IC 9513 

INFORMATION CIRCULAR/2009 

nd 

AMERICAN CONFERENCE ON

HUMAN VIBRATION 

June 4-6, 2008

Proceedings 

Organized by:
 

 

 

 

 

 

Information Circular 9513 

Proceedings of the Second American Conference 

on Human Vibration 

Chicago, IL 

June 4–6, 2008 

Technical Editors: Farid Amirouche, Ph.D., and Alan G. Mayton, C.M.S.P., P.E. 

Document Editor: Robert J. Tuchman 

DEPARTMENT OF HEALTH AND HUMAN SERVICES
 

Centers for Disease Control and Prevention
 

National Institute for Occupational Safety and Health
 

Pittsburgh Research Laboratory
 

Pittsburgh, PA
 

June 2009
 
 

 

 

 

       

This document is in the public domain and may be freely copied 

or reprinted. 

Disclaimer 

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do not constitute NIOSH endorsement of the sponsoring organizations or their programs or 

products. Furthermore, NIOSH is not responsible for the content of these Web sites. All web 

addresses referenced in this document were accessible as of the publication date. 

The views expressed by non-NIOSH authors in these proceedings are not necessarily those of 

NIOSH. 

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www.cdc.gov/niosh/eNews. 

DHHS (NIOSH) Publication No. 2009–145 

June 2009 

SAFER • HEALTHIER • PEOPLETM
Table of Contents
 

 Page 

Foreword............................................................................................................................ iii
 

Acknowledgments.............................................................................................................. iv
 

Conference Organizing Committee ................................................................................... iv
 

Human Body Vibration Scientific Committee................................................................... iv
 

Introduction ....................................................................................................................... 1
 

Keynote Speakers............................................................................................................... 5
 

Podium Presentations
 

Session I: Epidemiology and Standards I ................................................................... 7
 

Session II: New Technologies in Human Vibration ................................................... 14
 

Session III: Whole-Body Vibration I.......................................................................... 25
 

Session IV: Human Body Modeling and Vibration I.................................................. 36
 

Session V: Whole-Body Vibration II.......................................................................... 47
 

Session VI: Human Body Modeling and Vibration II ................................................ 56
 

Session VII: Hand-Arm Vibration.............................................................................. 67
 

Session VIII: Health Effects ....................................................................................... 80
 

Session IX: Epidemiology and Standards II ............................................................... 91
 

Session X: Whole-Body Vibration III ....................................................................... 110
 

Poster Session .................................................................................................................... 121
 

Index of Authors ................................................................................................................ 136
 
 

 

 

Foreword
 

We are proud to have cosponsored the Second American Conference on Human Vibration in 

Chicago, Illinois. Much hard work and diligent effort went into making this meeting a success 

and an avenue for future work in human vibration and health initiatives. The goal and the main 

thrust of the conference were to provide a forum for scientists, engineers, medical doctors, 

industrial hygienists, and educators to learn and advance research/education in the unique area of 

human body vibration. In promoting health and safety and in stimulating progress, leaders in the 

field were invited to share their insight and expertise in addition to the excellent and plausible 

papers on the presentation schedule. 

We hope that the proceedings of the conference, published here, will serve as a means of 

continuing the dialogue. 

This unique forum afforded participants opportunities to learn firsthand what their peers and 

colleagues are working on and to exchange information on a variety of relevant topics including 

human response, human modeling, experimental design, sensors, new technologies, and 

epidemiology studies in human responses to hand-transmitted and whole-body vibration. This 

research is essential for better understanding the risk factors for adverse effects related to 

vibration and for designing more effective interventions to prevent painful and potentially 

disabling work-related injuries. 

This conference addressed contemporary issues regarding occupational health, prevention 

measures, and scientific data collection used to study the complex, dynamic human response to 

vibration. The agenda included a rich and diverse scientific program as researchers and medical 

professionals from around the world gathered to examine human responses to hand-transmitted 

vibration and whole-body vibration. 

Special thanks are extended to the University of Illinois at Chicago for hosting the Second 

American Conference on Human Vibration as well as the scientific presenters from both the U.S. 

and abroad who shared their work and participated in advancing the science toward achieving 

safer and healthier workplaces. 

Christine M. Branche, Ph.D. 

Acting Director 

National Institute for Occupational Safety and Health 

Centers for Disease Control and Prevention 

iii
 
 

 

 

 

 

 

 

ACKNOWLEDGMENTS
 

The success of the Second American Conference on Human Vibration (2nd ACHV) could not 

be achieved except by the contributions of many. The conference Chair and Co-chair Farid 

Amirouche and Alan Mayton express their thanks and appreciation to the following individuals 

and organizations: the keynote speakers – Dr. Anthony Brammer, Mr. Thomas A. Broderick, 

Dr. Frank Buczek, Jr. (on behalf of Dr. John Howard), Dr. Mark Gonzalez, Dr. Rosemary Sokas; 

all of the reviewers who assisted in the technical review process including Kristine Krajnak, Ren 

Dong, John Wu, and Oliver Wirth at the Health Effects Laboratory Division (HELD) of the 

National Institute for Occupational Safety and Health (NIOSH), Morgantown, WV, and the 

Human Body Vibration Scientific Committee; Robert J. Tuchman, CDC Writer-Editor Services 

Branch, for his valuable insights and outstanding support in the editing, organization, and 

assembly of the final document; David Caruso (PRL) for designing the document cover, 

conference announcement, and call for papers; and Jill Raufus (CDC-MASO) for her support in 

organizing the review process and assembling this document. 

2nd ACHV Organizing Committee 

Farid Amirouche1 

Bertrand Valero1 

Kimberly Balogh1 

Urszula Sas1 

1

Department of Mechanical and Industrial Engineering, University of Illinois at Chicago 

Alan Mayton2 

Christopher Jobes2 

2

Pittsburgh Research Laboratory, National Institute for Occupational Safety and Health 

Human Body Vibration Scientific Committee 

Farid Amirouche (Chairman) University of Illinois at Chicago 

Thomas Armstrong University of Michigan 

Paul-Émile Boileau IRSST, Canada 

Anthony Brammer National Research Council, Canada 

Martin Cherniack University of Connecticut 

Ren Dong NIOSH – HELD 

Thomas Jetzer Occupational Medicine Consultants 

Bernard Martin University of Michigan 

Robert Radwin University of Wisconsin, Madison 

Subhash Rakheja Concordia University, Canada 

Douglas Reynolds University of Nevada, Las Vegas 

Danny Riley Medical College of Wisconsin 

Suzanne Smith U.S. Air Force Research Laboratory 

Donald Wasserman Human Vibration Consultant 

Jack Wasserman University of Tennessee, Nashville 

David Wilder University of Iowa 

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ACRONYMS AND ABBREVIATIONS
 

1-D one-dimensional 

AAALAC Association for Assessment and Accreditation of Laboratory Animal Care 

ACGIH American Conference of Governmental Industrial Hygienists 

ADAMS Automatic Dynamic Analysis of Mechanical Systems 

ANCOVA analysis of covariance 

ANOVA analysis of variance 

ANSI American National Standards Institute 

APMS apparent mass 

ASSE American Society of Safety Engineers 

BMD bone mineral density 

BMI body mass index 

BPF blade passage frequency 

BS British Standard 

CCM compensatory control model 

CDC Centers for Disease Control and Prevention 

CPT current perception threshold 

DPOAE distortion product otoacoustic emission 

EAV exposure action value 

ECM extracellular matrix 

ELV exposure limit value 

EMG electromyography, electromyogram 

EU European Union 

FAI fast-adapting type I (receptor) 

FBF finger blood flow 

FEA finite-element analysis 

fMRI functional magnetic resonance imaging 

FST finger skin temperature 

GPS global positioning system 

HAV hand-arm vibration 

HAVS hand-arm vibration syndrome 

HGCZ health guidance caution zone 

IFF interstitial fluid flow 

IRSST Institut de recherche Robert-Sauvé en santé et en sécurité du travail

 (Occupational Health and Safety Research Institute Robert-Sauvé, Montreal,

 Quebec, Canada) 

ISO International Organization for Standardization (Geneva, Switzerland) 

LHD load-haul-dump 

MSD musculoskeletal disorder 

MTVV maximum transient vibration value 

NAICS North American Industry Classification System 

NASA National Aeronautics and Space Administration 

NCV nerve conduction velocity 

NE norepinephrine 

v
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NIHL noise-induced hearing loss 

NIOSH National Institute for Occupational Safety and Health 

NSERC Natural Sciences and Engineering Research Council (Canada) 

OEL occupational exposure limit 

Pabs power absorbed 

PDA personal digital assistant 

PEMF pulsed electromagnetic field 

PSD power spectral density 

PVC polyvinyl chloride 

RDS response dose spectrum 

rms root-mean-square 

ROS reactive oxygen species 

RS response spectrum 

rss root-sum-of-squares 

S&H safety and health 

SAI slow-adapting type I (receptor) 

SD standard deviation 

SDOF single degree of freedom 

SDOFS single degree of freedom system 

SEM standard error of the mean 

SMC smooth muscle cell 

SPL sound pressure level 

STHT seat-to-head transmissibility 

SUV sport utility vehicle 

TTS temporary threshold shift 

TWA time-weighted average 

UIC University of Illinois at Chicago 

VDV vibration dose value 

VPA vibration power absorption 

VPT vibrotactile perception threshold 

WBV whole-body vibration 

WBVT whole-body vibration therapy 

WFD white finger disease 

vi
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UNIT OF MEASURE ABBREVIATIONS 

cm centimeter 

cm/ms centimeters per millisecond 

dB decibel 

dBA decibel, A-weighted 

dbNA decibel nível de audição 

df degree of freedom 

g gram 

g acceleration due to gravity (1 g = 9.80665 m/s2

) 

G gauss 

GPa gigapascal 

hr hour 

Hz hertz 

in inch 

kg kilogram 

kHz kilohertz 

km kilometer 

km/hr kilometers per hour 

kN kilonewton 

m meter 

m3 cubic meter 

m/s meter per second 

m/s2, ms

−2, m/s/s meter per second squared 

mA milliampere 

mg/kg milligram per kilogram 

mg

2 square milligram 

min minute 

mL milliliter 

mm millimeter 

mM millimolar 

mm Hg millimeters of mercury 

MPa megapascal 

mph mile per hour 

mt metric ton 

mV/cm millivolt per centimeter 

N newton 

nm nanometer 

Nm net moment 

N/m2 newton per square meter 

psi pound-force per square inch 

rad/s/s radian per second squared 

sec second 

μm micrometer 

μM micromolar 

μM2 square micromolar 

μT microtesla 

°C degree Celsius 

vii
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

INTRODUCTION
 

There is a saying, “If it moves, it vibrates.” This is especially true in our modern industrial environments, 

where workers use powered tools, machinery, vehicles, and heavy equipment. How workers are affected 

by these elements of the industrial working environment is a concern of health professionals, governments, and scientists around the world. How to adequately assess the effects of human vibration exposure 

is an equally important issue. 

The human body comprises a dynamic structure that is living, intelligent, and complex. Consequently, 

it is not unreasonable to consider that exposing the body to an array of vibration environments would 

result in outcomes that are not necessarily simple or easily predictable. Sensations caused by vibration 

may include nausea, annoyance, discomfort or pain, and exhilaration or pleasure. Many factors contribute 

to the effects of vibration on humans, including the characteristics of the motion and the exposed individual, the activities of the exposed individual, and various elements of the environment. There have been 

attempts to summarize the effects of occupational vibration exposures by simply recommending the 

avoidance of certain frequencies of vibration or by providing a graphical method, i.e., a single curve 

displaying all human responses to all frequencies. However, such efforts have not withstood the scrutiny 

of scientific research and analysis. Thus, attendees and participants at this professional gathering now 

have the rare opportunity to benefit from the technological advances and new scientific research to 

enhance their understanding of human responses to vibration that suggest more than a simplistic 

approach. 

In the tradition of the First American Conference on Human Vibration (1st ACHV) held in Morgantown, 

WV, June 2006, the 2nd ACHV provides a forum for scientists, engineers, medical doctors, industrial 

hygienists, and educators to learn and advance research and education in the specialized area of human 

body vibration. The conference was organized by the Mechanical and Industrial Engineering Department, 

University of Illinois at Chicago, with support from the National Institute for Occupational Safety and 

Health (NIOSH), Pittsburgh Research Laboratory. As with the first conference, the 2nd ACHV provides 

the unique opportunity to learn about the current activities of peers and colleagues and to exchange 

information on topics of interest such as human response, human modeling, experimental design, sensors, 

new technologies, and epidemiological studies of human responses to hand-transmitted and whole-body 

vibration. The conference organizers hope that the publication of these conference proceedings continues 

to foster new research and technological advances to reduce health hazards associated with occupational 

vibration exposures. 

Farid Amirouche
 

Conference Chair
 

Alan G. Mayton
 

Conference Co-Chair
 

1
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1 Outline of the Proceedings

1

This section was compiled by Ren G. Dong, Kristine Krajnak, and Thomas W. McDowell of the NIOSH Health 

Effects Laboratory Division, Morgantown, WV. 

2
 

A conceptual model of the major factors influencing human vibration exposure and health effects, as well 

as their general relationships, is shown in Figure 1.

 

 

 

 

 

 

 

 

 

 

 

 

 

Psychophysical responses 

Physiological responses 

Pathological responses 

Environments: 

temperature, noise, 

etc. 

Individual genetic 

variability, health 

condition, age, etc. 

Signs and symptoms of vibration-induced 

disorders or diseases 

Biodynamic responses: 

Vibration-induced 

motion, stress, strain, 

and power absorption 

Behaviors and influencing factors 

Vibration 

sources and 

inputs to 

human 

bodies 

Figure 1.—Conceptual model of human vibration exposure and health effects. 

 Most of the studies presented at this conference 

involved the measurement, understanding, and/or assessment of these factors and their relationships. 

Other studies focused on the control or mitigation of vibration transmitted to the human body or the 

biological responses of tissues to vibration exposure. Therefore, the proceedings are organized in terms of 

the major factors and their relationships. 

Specific sessions focused on the measurement of whole-body (III, V, X) and hand-transmitted (VII) 

vibration in field and laboratory settings. Studies presented in other sessions (I, VIII, and IX) 

characterized the physiological responses of humans and animals to vibration and described how 

vibration may act on the cellular and molecular levels to induce these physiological changes. Studies 

describing the development and use of mechanical models for assessing the effects of vibration on the 

human body were presented in Session II. A number of presentations throughout this conference also 

focused on the assessment of current standards; presented data can be used to update and improve those 

standards. Together, the presentations in these 10 sessions covered state-of-the-art approaches for 

measuring, assessing, and mitigating the effects of human exposures to occupational vibration. 

Assessment of the State of Human Body Vibration Research 

To aptly assess the state of human body vibration research, we refer back to the insights of Michael J. 

Griffin, a keynote speaker at the 1st ACHV. Dr. Griffin sought to encapsulate this field of study in terms 

of “what we know that we know, what it is sometimes claimed that we know, and what we know that we 

do not know about the relation between exposures to vibration and our health.” He speculated also on 

“what we do not know that we do not know” [Griffin 2006]. 

Griffin [2006] explains that “[t]here are many unknowns in the field of human responses to vibration. 

Not all would agree on what is known and what is unknown.” With regard to hand-transmitted vibration, 

Griffin states: “We know that exposures to hand-transmitted vibration result in various disorders of the 
 

 

 

 

 

 

 

 

 

 

 

 

 

hand, including abnormal vascular and neurological function. Not all frequencies, or magnitudes, 

or durations of hand-transmitted vibration cause the same effects.” 

We may claim to know that: 

To enable exposures to be reported and compared, they are “measured” and “evaluated” using defined 

(e.g., standardized) procedures. This involves identifying what is to be measured and specifying how 

it is expressed by one (or a few) numbers. Summarizing a vibration exposure in a single value 

involves assuming the relative importance of components within the vibration (e.g., different 

magnitudes, frequencies, directions, and durations), so standards define “weightings” for these 

variables. The importance of the weighted values may also be suggested, allowing “assessments” 

according to a criterion (e.g., the probability of a specific severity of a specific disease). 

Standards for the measurement and evaluation of hand-transmitted vibration define a frequency 

weighting and time dependencies that allow the severity of vibration exposures to be assessed and the 

probability of finger blanching to be predicted. [Griffin 2006] 

What we do not know is that: 

[T]he frequency weighting in current standards reflects the relative importance of different frequencies and axes of vibration in producing any specific disorder. We do not know whether the 

energy-based daily time-dependency inherent in A(8) reflects the relative importance of vibration 

magnitude and daily exposure duration. Consequently, the relation between A(8) and the years of 

exposure to develop finger blanching, as in an appendix to ISO 5349-1 (2001), is not well-founded. 

We do not know, or at least there is no consensus on, the full extent of the disorders caused by handtransmitted vibration (e.g., vascular, neurological, muscular, articular, central), or the pathogenesis of 

any specific disorder caused by hand-transmitted vibration, or the roles of other factors (e.g., ergonomic factors, environmental factors, or individual factors). We know that acute exposures to handtransmitted vibration cause both vascular and neurological changes analogous to the changes seen in 

those occupationally exposed to hand-transmitted vibration, but we do not yet know how the acute 

changes relate to the chronic disorders. [Griffin 2006] 

Regarding whole-body vibration, Griffin [2006] reports: “We know that many persons experience back 

pain and that some of these are exposed to whole-body vibration. We know that in the population at large, 

occupational exposures to whole-body vibration are not the main cause of back problems and that 

ergonomic factors (e.g., lifting and twisting) and personal factors are often involved. We know vibration 

and shock can impose stresses that could supplement other stresses.” We may claim to know that 

“[m]easurement methods and evaluation methods have been defined in which the frequencies, directions, 

and durations are weighted so as to predict the relative severity of different vibrations and indicate the 

magnitudes that might be hazardous.” What we do not know is that “[w]e are not able to predict the 

probability of any disorder from the severity of an exposure to whole-body vibration. We do not know 

whether there is any disorder specific to whole-body vibration or what disorders are aggravated by 

exposure to whole-body vibration. We do not know the relative importance of vibration and other risk 

factors in the development of back disorders.” 

Griffin [2006] concludes that: 

Providing guidance to others involves compromises—a perceived need, or other argument, that may 

outweigh the cautious interpretation of scientific evidence. Standards for measuring and evaluating 

human exposures to vibration use uncertain frequency weightings and time dependencies but allow 

legislation for the protection of those exposed. The standards may appear useful, but it is prudent to 

3
 
 

 

 

 

distinguish between standards and knowledge—between what is accepted to reach a consensus and 

what can be accepted as proven. Standards may guide actions but not understanding. 

Where reducing risk solely involves reducing vibration magnitude or exposure duration, ill-founded 

evaluation methods will not increase risk. Where prevention involves a redistribution of vibration over 

frequencies or directions, or balancing a change in magnitude with a change in duration, an 

inappropriate evaluation method can increase risk. For example, the hand-transmitted vibration 

frequency weighting, which may be far from optimum, implies that gloves give little beneficial 

attenuation, whereas a different weighting might indicate that gloves can be a useful means of 

protection. 

What do we not know that we need to know? Not all appreciate the benefits of placing more reliance 

on traceable data than on consensus. Traceability is fundamental to quality systems but deficient in 

current standardization. Standards can comfort their users—justifying actions without resort to 

understanding—while concealing assumptions that may prevent the minimization of the risks of injury 

from exposures to vibration. 

Reference 

Griffin MJ [2006]. Health effects of vibration: the known and the unknown. In: Proceedings of the First 

American Conference on Human Vibration. Morgantown, WV: U.S. Department of Health and Human 

Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and 

Health, DHHS (NIOSH) Publication No. 2006–140, pp. 3–4. 

4
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

KEYNOTE SPEAKERS
 

Frank Buczek, Jr. (on behalf of Dr. John Howard, Director, National Institute for Occupational Safety and Health (NIOSH), Washington, DC) 

Frank L. Buczek, Jr., Ph.D., is Chief of the Engineering & Control Technology Branch, 

in the Health Effects Laboratory Division, of the National Institute for Occupational 

Safety & Health in Morgantown, WV. He also serves as Coordinator for the Musculoskeletal Disorders (MSD) Cross Sector Program at NIOSH. He holds adjunct appointments at several universities, is a Past President of the Gait and Clinical Movement 

Analysis Society, and serves on MSD-related study sections for the National Institutes of Health (NIH). 

Building upon an undergraduate foundation in Mechanical Engineering, Dr. Buczek earned his doctorate 

in Human Movement Biomechanics from the Pennsylvania State University in 1990, where early research 

efforts challenged slip resistance levels considered adequate for flooring at that time. During postdoctoral 

work at NIH, he specialized in advanced kinematic and kinetic modeling of anatomical joints. Since 1995, 

he has applied this expertise to pediatric gait analysis, leading most recently to collaboration on muscle 

actuated, full-body simulations of normal and pathological gait. 

Mark Gonzalez 

Mark Gonzalez, M.D., is a Professor at the University of Illinois at Chicago (UIC), 

Department of Orthopedic Surgery. Mark has been a Fellow of the American Academy of 

Orthopedic Surgeons since 1993 and is Chairman of Orthopedic Surgery, Cook County 

Hospital, Chicago, IL. Mark received his B.S. in biochemistry from the University of 

Illinois-Champaign in 1976 and his M.D. from UIC in 1980. He completed his orthopedic 

residency at UIC during 1981–1985 and fellowships at Ohio State University and the 

University of Louisville. He is currently the Chairman of the Department of Orthopedic Surgery and is 

completing his Ph.D. in mechanical engineering at UIC. He is the author of more than 100 technical 

papers and has been a Fellow of the American Academy of Orthopedic Surgeons since 1992. His current 

research includes the areas of nerve regeneration, orthopedic biomechanics, and micro-electro-mechanical 

system (MEMS) sensor devices. 

Anthony Brammer 

Anthony (Tony) Brammer, Ph.D., is a Professor of Medicine at the University of 

Connecticut Health Center, and works in the Ergonomic Technology Center of 

Connecticut. He is also a Visiting Scientist at the National Research Council of Canada, 

where he has conducted research in acoustics for most of his career, and an Associate of 

Envir-O-Health Solutions, which is an Ottawa company specializing in solutions to 

environmental and occupational health problems. Dr. Brammer received a National 

Research Council Research Fellowship in 1968, the National Research Council’s Achievement Award in 

1994, and the National Research Council’s Institute for Microstructural Sciences’ Award in 2001, and the 

International Commission on Occupational Health’s Service Award in 2006. He is a Fellow of the Royal 

Society of Medicine and of the Acoustical Society of America, and is past Chairman of the Scientific 

Committee on Vibration and Noise of the International Commission on Occupational Health. He is also 

Convener (Chairman) of Working Groups of the International Organization for Standardization (ISO) on 

vibrotactile perception and biodynamic modeling. 

5
 
 

 

 

 

 

 

 

 

 

 

 

 

Thomas A. Broderick 

Thomas A. Broderick, M.S., is Executive Director, Construction Safety Council, 

Chicago, IL. Tom has been involved in the construction field since the early 1970s. He 

has been a construction worker, co-owner of a small construction company, and a construction safety professional. During his safety career, he has managed safety programs at 

projects including nuclear and fossil fuel power plants, paper mills, and other large jobs 

for contractors such as Blount Construction Co., Stone & Webster Engineering Corp., and the Rust Engineering Co. Tom holds a B.S. degree in speech communications and a master’s degree in safety management. He is currently the executive director of the not-for-profit Chicagoland Construction Safety Council 

and the Construction Safety Council. In that capacity he is the director of the annual Construction Safety 

Conference in Chicago, the largest educational gathering in the United States focused solely on construction environmental health and safety (EHS) issues. Tom was nominated in 2001 by Secretary of Labor 

Elaine Chao to serve on the congressionally mandated Advisory Committee for Construction Safety and 

Health, a committee on which he still serves. He is also past president of Veterans of Safety International 

and a commissioner on the National Commission for the Certification of Crane Operators. He has 

authored numerous articles on EHS and has contributed to several texts in the field. 

Rosemary Sokas 

Rosemary Sokas, M.D., M.S., is a Professor of Environmental and Occupational Health 

Sciences (EOHS), University of Illinois at Chicago. Her academic background is: 

M.D., Boston University, 1974; M.S., Physiology, Harvard University, 1981; MSPH, 

Harvard University, 1980; and BSMLS, Medical Science, Boston University, 1974. Her 

research interests include applied, translational occupational safety and health organizational work targeting small businesses and vulnerable populations. Her teaching interests include 

problem-based occupational and environmental health/integration of EOHS into public health and primary care. 

6
 
Session I: Epidemiology and Standards I 

Chair: Kristine Krajnak 

Co-Chair: Thomas McDowell 

Presenter 

R. House 

University of Toronto 

Title 

Current Perception Threshold, Nerve Conduction Studies, 

and the Stockholm Sensorineural Scale in Workers With 

Hand-Arm Vibration Syndrome 

Page 

8 

S. Govindaraju 

Medical College of 

Wisconsin 

Mechanism of Vibration-Induced Smooth Muscle Cell 

Injury in the Rat Tail Artery 

10 

K. Krajnak 

National Institute for 

Occupational Safety and 

Health (NIOSH) 

Sensory Nerve Responses to Acute Vibration Are 

Frequency-Dependent in a Rat Tail Model of Hand-Arm 

Vibration Syndrome 

12 

7
 
 

 

 

 

 

 

 

CURRENT PERCEPTION THRESHOLD, NERVE CONDUCTION STUDIES,
 

AND THE STOCKHOLM SENSORINEURAL SCALE IN WORKERS WITH
 

HAND-ARM VIBRATION SYNDROME
 

Ron House,1 and Michael Manno1 

1

University of Toronto and St. Michael’s Hospital, Toronto, Ontario, Canada
 

Kristine Krajnak,2

2

Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 


Morgantown, WV
 

Introduction 

Neurological abnormalities are frequently reported in workers using vibrating tools. 

The Stockholm sensorineural scale attempts to classify the neurological component of hand-arm 

vibration syndrome. However, it is unclear what the underlying neurological damage consists of, 

how it should be measured, and how it relates to the Stockholm scale. 

This study was carried out to examine the relation between the Stockholm sensorineural 

scale and tests of neurological abnormities, including measurement of current perception threshold (CPT) and nerve conduction in workers using vibrating tools. 

Methods 

All of the study participants had been exposed to hand-arm vibration at work and were 

assessed at St. Michael’s Hospital, Toronto, Ontario, Canada, over a 4-year period ending in 

2003. The assessment consisted of an occupational and medical history, physical examination 

with emphasis on the neurological examination of the upper extremities, and neurological tests 

including measurement of CPT and nerve conduction. The results of the medical history and 

physical examination were used to determine the Stockholm sensorineural scale. The CPT 

measurements, nerve conduction measurements, and determination of the Stockholm scale were 

all carried out in a fashion blinded to each other. 

Polychotomous logistic regression was used to examine the relation between the Stockholm scale dependent variable and various independent variables including (1) the CPT results 

for the median and ulnar nerve at 5250 and 2000 Hz and (2) the presence of neuropathy on the 

nerve conduction study (median, ulnar, digital). 

Results 

There were 155 study participants who worked in a variety of industries, with mining 

being the most prevalent. The workers were all male and had an average age of 45.9 ± 11.32 

years and an average duration of exposure to vibrating tools of 21.8 ± 12.03 years. The 

distribution of subjects in the Stockholm scale categories 0, 1, ≥2 was as follows: right hand – 

51, 81, 23; left hand – 52, 83, 20. The nerve conduction studies indicated that 40.6% of subjects 

had peripheral neuropathy in the right hand (34.8% median; 6.5% ulnar, 1.3% digital) and 30.3% 

had peripheral neuropathy in the left hand (23.9% median; 6.5% ulnar, 1.3% digital). The sum of 

the percentages of the specific neuropathies exceeded the overall total percentage of subjects 

with peripheral neuropathy in each hand because some subjects had more than one neuropathy. 

None of the CPT measurements at any frequency was found to be associated with any type of 

8
 
 

 

 

 

 

 

neuropathy. The polychotomous logistic regression results indicated that the CPT measurements 

at 2000 Hz were the main predictor variables for the Stockholm scale. In the right hand, the 

only statistically significant independent variable was the CPT median nerve value at 2000 Hz 

(p < 0.0001). In the left hand, the main statistically significant independent variables were the 

CPT median nerve value at 2000 Hz (p = 0.001) and the CPT ulnar nerve value at 2000 Hz 

(p = 0.0007). None of the nerve conduction abnormalities was significantly associated with the 

Stockholm scale in the regression results in either hand. 

Discussion 

The results indicated that the main neurological test predictive of the Stockholm scale 

was the CPT measurement at 2000 Hz. This independent variable measures damage to the large 

myelinated fibers of the fingers. 

A previous study by Lander et al. [2007] in the same setting but using different data suggested an association between overall CPT results for the ulnar nerve and the Stockholm scale. 

The results presented here provide more detailed information about the relation between 

frequency-specific CPT measurements and the Stockholm scale. Our findings are similar to those 

described by Kurozawa and Nasu [2001]. 

There is also evidence of similar effects on CPT in rats exposed to vibration [Krajnak 

et al. 2007], as well as histological evidence of damage to large myelinated fibers due to vibration exposure in animals [Chang et al. 1994]. These findings provide biological plausibility for 

damage to the large myelinated fibers in workers exposed to vibration and suggest overall coherence of evidence at the histological, animal, and human level. 

Workers exposed to vibration also have a high prevalence of neuropathy proximal to the 

hand. However, our results indicated that these proximal neuropathies were not associated with 

the Stockholm scale. Also, the proximal lesions did not explain the CPT findings in our study. 

Therefore, the CPT abnormalities, which were clearly associated with the Stockholm scale, seem 

to indicate a second type of distal neurological lesion in the fingers due to vibration exposure. 

Further research should focus on the best methods of measurement and the functional 

significance of these distal neurological lesions. In addition, the role of vibration and ergonomic 

factors in the etiology of the proximal neuropathies needs to be understood in more detail. It is 

also evident that improvement is needed in the classification system used for the neurological 

damage associated with vibration. Improved understanding in these areas should lead to 

enhanced prevention efforts. 

References 

Chang KY, Ho ST, Yu HS [1994]. Vibration induced neurophysiological and electron 

microscopy changes in rat peripheral nerves. Occup Environ Med 51(2):130–135. 

Krajnak K, Waugh S, Wirth O, Kashon ML [2007]. Acute vibration reduces Abeta nerve 

fiber sensitivity and alters gene expression in the ventral tail nerves of rats. Muscle Nerve 36(2): 

197–205. 

Kurozawa Y, Nasu Y [2001]. Current perception thresholds in vibration-induced neuropathy. Arch Environ Health 56(3):254–256. 

Lander L, Lou W, House R [2007]. Nerve conduction studies and current perception 

thresholds in workers assessed for hand-arm vibration syndrome. Occup Med (Lond) 57(4):284– 

289. 

9
 
 

 

 

SMC

 

 

 

SMC

Figure 1: Mechanism of vibration injury 

 

 

 

 

 

 

MECHANISM OF VIBRATION-INDUCED SMOOTH MUSCLE CELL INJURY
 

IN THE RAT TAIL ARTERY
 

Sandya Govindaraju, James Bain, and Danny Riley
 

Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 


Milwaukee, WI
 

Introduction 

Vasospastic blanching of the fingers is a major complication of hand-arm vibration syndrome, an occupational disorder in workers using handheld power tools. Our rat tail vibration 

model, which simulates hand-transmitted vibration, was developed to investigate the cellular 

mechanism of vibration injury [Curry et al. 2002]. Vibration causes vasoconstriction and smooth 

muscle cell (SMC) vacuoles in the rat tail artery [Curry et al. 2005]. Vibration injury of SMC in 

arteries is hypothesized as a two-step process (Figure 1).

Vibration

Vasoconstriction

Mechanical

displacement

vacuole formation

Vacuole transformation

1. resorption

2. detachment

3. fragmentation

vacuole reformation

••

•••• •

• • •

•

•

•

•

•

• 1 •

2

3

Vibration 

Vasoconstriction 

Mechanical

displacement 

vacuole formation 

Vacuole transformation 

1. resorption 

2. detachment 

3. fragmentation 

SMC 

vacuole reformation 

••

•••• •

• • •

•

•

•

•

•

• 1 •

2

3 ••

•••• •

• • •

•

•

•

•

•

••

••

•••• • 

• • • 

•

•

• 

•

• 

• 1 •

2 

3 

Figure 1.—Mechanism of vibration injury. 

 The first step is SMC contraction and 

vacuole formation, stimulated by vibration via a centrally mediated, somatosympathetic neural 

response. The second step occurs when the protruding vacuoles are detached from the cell by the 

mechanical force of vibration. Detachment could generate persistent vacuoles on the one hand 

and increased fragmentation on the other. Other vacuoles may be resorbed by the parent cell 

during SMC relaxation. The number and size of 

vacuoles formed and lost will determine the 

severity of vascular damage induced by vibration. 

The present study addressed two questions: 

(1) Do vibration-induced vasoconstriction and 

vacuole formation occur in SMC of rats 

anesthetized to blunt central nervous system 

vasomotor activity? (2) Does vibration of 

anesthetized rats disrupt vacuoles generated by 

norepinephrine (NE)-induced vasoconstriction 

pretreatment? 

Methods 

Awake rats were restrained on a nonvibrating platform with their tails taped to a vibrating 

stage. Vibration consisted of linear vertical oscillations with a frequency of 60 Hz, peak-to-peak 

amplitude of 0.98 mm, and an acceleration of 49 m/s2

 (rms) for 4 hr. Sham vibration rats were 

treated similarly but not vibrated. NE (1 mM) in Hanks Balanced Salt Solution bathed for 15 min 

the caudal artery exposed by a ~5-cm ventral skin incision. Following vibration, the tail segment 

C7 was removed and immersion-fixed in 4% glutaraldehyde, 2% paraformaldehyde in 

cacodylate buffer (pH 7.4). Arteries were postfixed in 1.3% osmium tetraoxide and embedded in 

epoxy resin for semithin (0.5 μm) and ultrathin (~70 nm) sectioning. Version 1.28v ImageJ 

software was used to count vacuoles, measure lumen circumference, and determine internal 

elastic membrane length in toluidine blue-stained semithin sections. Vacuoles counted were 

round to oval-shaped intracellular inclusions (2–12 μm), clear or homogeneously dense material. 

10
 
 

 

 

 

Results 

Vasoconstriction and 

vacuole formation occurred 

following awake-vibration and 

NE treatment. Vacuole number 

remained high 4 hr after exposure 

to NE (Table 1). 

1 Table 1.—Lumen size and vacuole number 

Treatment	 No. of rats	 

per group	 Lumen SMC 2 vacuoles

Awake-sham	 

Awake-vibration 

7 

7 

52.3 ± 3.8 3

42.1 ± 3.6 

3.6 ± 2.3 4

44.8 ± 6.1 

Anesthesia-sham 6 54.5 ± 3.3 2.0 ± 1.0 

Anesthesia-vibration 6 53.4 ± 3.1 4.0 ± 1.0 

Vehicle application 

NE	 

NE + anesthesia-sham 

5 

7 

6 

59.8 ± 3.2 3

29.4 ± 2.0 

61.0 ± 2.7 

0.0 ± 0.0 3

106.6 ± 16.3 4

44.5 ± 8.3 

NE + anesthesia-vibration 8 52.0 ± 4.2 0.4 ± 0.2 1 Percent ratio of the lumen circumference to the internal elastic mem 

brane length. 2 Total numbers per section. 

3 Significantly different from all other groups. 4 Significantly different (p<0.05) from all other groups, except each 

other, when tested using the Student-Newman-Keuls pairwise com 

parison test. 

Compared to the awakesham group, the NE + anesthesiavibration group had larger areas 

of dense filamentous matrix 

(Figure 2).

 

 

 

Figure 2.—Electron micrographs of extracellular matrix (ECM) of the awake-sham 

(A and D), awake-vibration (B and E), and NE + anesthesia-vibration (C and F) 

groups. Bar in A equals 3.6 μm for A through C and 440 nm for D through F. 

 Compared to awakesham, the awake-vibration and 

NE-anesthesia-vibration groups 

had a higher content 

of cellular membranous and particulate 

debris. The cellular 

debris in the NE + 

anesthesia-vibration 

group was larger 

than that of the 

awake-vibration 

group. 

­

­

Summary and Conclusions 

•	 Anesthesia prevents vibration-induced vasoconstriction and vacuole formation. 

•	 Vacuoles preformed by NE treatment are disrupted by vibration, as indicated by increased 

cellular debris in the ECM. 

•	 Vibration causes cell injury in a two-step process: inducing vasoconstriction to generate 

vacuoles and disrupting vacuoles to cause loss of portions of SMC. 

•	 Repeated cell injury over time may compromise vascular function and trigger adaptive cellular mechanisms to combat vibration injury. 

References 

Curry BD, Bain JLW, Yan J-G, Zhang LL, Yamaguchi M, Matloub HS, Riley DA 

[2002]. Vibration injury damages arterial endothelial cells. Muscle Nerve 25(4):527–534. 

Curry BD, Govindaraju SR, Bain JL, Zhang LL, Yan JG, Matloub HS, Riley DA [2005]. 

Evidence for frequency-dependent arterial damage in vibrated rat tails. Anat Rec A Discov Mol 

Cell Evol Biol 284(2):511–521. 

11
 
 

 

 

 

SENSORY NERVE RESPONSES TO ACUTE VIBRATION ARE FREQUENCYDEPENDENT IN A RAT TAIL MODEL OF HAND-ARM VIBRATION SYNDROME
 

Kristine Krajnak,1

 Stacey Waugh,1 G. Roger Miller,1

1

Engineering and Control Technology Branch, Health Effects Laboratory Division 

 and Michael L. Kashon2 

2

Biostatistics and Epidemiology Branch, Health Effects Laboratory Division 

National Institute for Occupational Safety and Health (NIOSH), Morgantown, WV 

Introduction 

Occupational exposure to hand-arm vibration through the use of powered handtools can 

result in reductions in tactile sensitivity. Acute exposures to vibration cause shifts in vibrotactile 

thresholds in exposed fingers that are affected by the frequency of the exposure, with exposure to 

midrange vibration frequencies (i.e., around 125 Hz) producing the greatest shifts [Maeda and 

Griffin 1994]. We have demonstrated that acute vibration exposure at 125 Hz results in a transient increase in sensory nerve thresholds to a 2,000-Hz transcutaneous stimulus in a rat tail 

model of hand-arm vibration syndrome [Krajnak et al. 2007]. The goal of this study was to determine how repeated exposures to vibration at frequencies that produce different biodynamic 

responses affect sensory nerve function in our rat tail model. 

Methods 

Animals. Male Sprague Dawley rats (8 weeks of age, n = 5 per group) were housed in 

AAALAC-accredited facilities. All procedures were approved by the NIOSH Animal Care and 

Use Committee and were in compliance with CDC guidelines for the care and use of laboratory 

animals. Vibration exposures were performed by restraining rats in a Broome-style restrainer and 

securing their tails to a vibration platform using 6-mm-wide straps that were placed over the tail 

every 3 cm. Restraint control animals were treated in an identical manner except that the tail 

platform was set on isolation blocks instead of a shaker. Rats were exposed to 4-hr bouts of 

vibration or restraint for 10 consecutive days at 0, 62.5, 125, or 250 Hz with a constant acceleration of 49 m/s2

 root-mean-square. Previous work in our laboratory has shown that vibration 

exposure at these frequencies and acceleration produce different magnitudes of transmissibility 

to the tail [Welcome et al. 2006]. An additional group of animals served as cage control rats. 

Current perception thresholds (CPTs) and mechanoreceptor sensitivity. Sensory 

nerve function was assessed by measuring CPTs with a Neurometer (Neurotron, Inc., Baltimore, 

MD). Transcutaneous nerve stimulation at 2,000 Hz was applied to the C10 region of the tail to 

determine the effects of vibration on Aβ nerve fiber sensitivity. The intensity of the stimulus was 

automatically increased in small increments until the rat flicked its tail. Aβ-nerve fibers are 

large-diameter, myelinated nerve fibers that carry information from mechanoreceptors to the 

central nervous system. Tests were repeated until the animals displayed two responses that were 

within 2 CPT (or 0.02 mA) of each other (two to three tests per animal). To determine if changes 

in sensory nerve responsiveness were accompanied by changes in mechanoreceptor sensitivity, 

the response to pressure induced by the application of 1- and 10-g von Frey filament was 

assessed. If animals flicked their tail, they were responsive; if not, they were nonresponsive. CPT 

and mechanoreceptor sensitivity tests were performed before (pretest) and immediately after 

(posttest) the vibration exposure on days 1 and 9 of the exposure. 

Data analyses. CPT data were analyzed using a mixed model three-way (condition × 

days of exposure × pre/post exposure) ANOVA where animal served as a random variable. The 

number of animals responding to stimulation with the von Frey filaments was analyzed using 

contingency table chi-square tests. Differences with p < 0.05 were considered significant. 

12
 
 

 

 

Results 

­

 

 

 

 

 

 

 

 

20 

30 

40 

50 

60 

70 

80 

90 

1 Day of Exposure	 90 

80 

9 Days of Exposure 

#A #A,B #A,B 

Cage Restraint 62.5 Hz 125 Hz 250 Hz 

Pre Exposure 

Post Exposure 

* 

Cage Restraint 62.5 Hz 125 Hz 250 Hz 

2000 Hz CPT (mA) 

2000 Hz CPT (mA) 

70 

60 

50 

40 

30 

20 

10 10 

0 0

Figure 1.—CPTs after vibration exposure. After 1 day of exposure, vibration at 125 Hz resulted in an 

increase in the 2,000-Hz CPT threshold (*greater than preexposure, p < 0.05). After 9 days of exposure, 

CPTs were reduced in all rats exposed to vibration (# less than day 1, p < 0.05). In addition, vibrated animals 

displayed lower thresholds than control animals after 9 days of exposure (A: different from cage controls; 

B: different from restraint controls, p < 0.05). 

 

 

 

 

 

 

 

0 

10 

20 

30 

40 

50 

60 

70 

%Animals Responding at 1g

Day 1 

Day 9 Figure 2.—Percentage of animals responding to mechano

receptor stimulation with a 1-g von Frey filament after 1 or 

9 days of vibration. The percentage of animals responding to 

stimulation with the filament was higher after 9 days of 

vibration exposure at 250 Hz than after 1 day (χ

2

, p < 0.04). 

No changes were seen with 10-g stimulation. 

Cage	 Restraint 62.5 Hz 125 Hz 250 Hz 

Discussion 

•	 As previously shown [Krajnak et al. 2007], a single exposure to vibration at 125 Hz results 

in an increase in the 2,000-Hz CPT. Similar responses to acute vibration are also seen in 

humans [Maeda and Griffin 1994]. 

•	 After 9 days of vibration exposure, 2,000-Hz thresholds were lower in vibrated than in control or restrained rats. In contrast, changes in mechanoreceptor sensitivity were seen only in 

rats exposed to 250 Hz, which is the frequency that generates the greatest biodynamic 

response in the tail [Welcome et al. 2006]. 

•	 Increased sensitivity to mechanical stimuli may serve as an early indicator of vibrationinduced nerve damage. 

References 

Krajnak K, Waugh S, Wirth O, Kashon ML [2007]. Acute vibration reduces Abeta nerve 

fiber sensitivity and alters gene expression in the ventral tail nerves of rats. Muscle Nerve 36(2): 

197–205. 

Maeda S, Griffin MJ [1994]. Temporary threshold shifts in fingertip vibratory sensation 

from hand-transmitted vibration and repetitive shock. Nagoya J Med Sci 57(Suppl):185–198. 

Welcome D, Dong RG, Krajnak KM [2006]. A pilot study of the transmissibility of the 

rat tail compared to that of the human finger. In: Proceedings of the First American Conference 

on Human Vibration (June 5–7, 2006). Morgantown, WV: U.S. Department of Health and 

Human Services, Public Health Service, Centers for Disease Control and Prevention, National 

Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2006–140, 

pp. 101–102. 

13
 
Session II: New Technologies in Human Vibration
 

Chair: Michael Griffin 

Co-Chair: Tom Jetzer * 

* Author unable to attend session. 


14
 

Presenter 

N. Shibata 

Japan National Institute of 

Occupational Safety and 

Health 

Title 

Comparison Between Biodynamic Response Parameters 

of the Same Subject Obtained From Two Different 

Vibration Systems 

Page 

15 

R. Stayner 

RMS Vibration Test 

Laboratory 

Suspended Seats for Reducing Exposure to Whole-Body 

Vibration: Improving Standard Tests to Reduce 

Interlaboratory Variations 

17 

S. D. Smith 

Wright-Patterson Air Force 

Base 

Multiaxis Seat Cushion Transmissibility Characteristics 19 

F. Amirouche 

University of Illinois at 

Chicago 

Comparison of the Performance of a Pneumatic Active 

Seat Suspension Using a Discrete and Fuzzy LogicBased Control Law 

21 

P. Marcotte 

Institut de recherche 

Robert-Sauvé en santé et 

en sécurité du travail 

(IRSST) 

Characterization of the Noise and Vibration Produced by 

Portable Power Tools Used in the Automotive Repair 

Industry 

23 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

COMPARISON BETWEEN BIODYNAMIC RESPONSE PARAMETERS OF THE 

SAME SUBJECT OBTAINED FROM TWO DIFFERENT VIBRATION SYSTEMS 

N. Shibata and S. Maeda
 

Japan National Institute of Occupational Safety and Health, Kawasaki, Japan
 

Introduction 

Biodynamic response data of the hand-arm system give us much information not only for 

understanding hand-transmitted vibration and its health effects, but also for designing lowvibration exposure handheld power tools. Although ISO 10068 (1998) specifies the free, mechanical impedance of the human hand-arm system at the driving point, this standard contains some 

recommendations partially based on unreliable data sets, which differ considerably from each 

other even if measured under similar experimental conditions. These differences are partly due to 

the difference in dynamic characteristics of the experimental systems used, which of course 

include handle geometry and its setup. In this study, data compatibility was examined for two 

hand-arm vibration systems—one installed at the Japan National Institute of Occupational Safety 

and Health, the other at the U.S. National Institute for Occupational Safety and Health (NIOSH)— 

by measuring biodynamic response parameters of the hand-arm system with the same subject. 

Methods 

The experiments were conducted in two laboratories: one at the U.S. NIOSH, the other at 

the Japan NIOSH. The configurations of the two hand-arm vibration systems were basically the 

same. These vibration exposure systems consisted of an electromechanical shaker, horizontally 

mounted on a solid base, which makes vibration in the Zh direction. The same force plates 

(Kistler 9286AA) were used to measure the feed force applied through the subject’s hand to 

instrumented handles connected to the shaft of the shaker. The handles, of the same design 

[Dong et al. 2004], were composed of the base and measuring cap between which two force sensors (Kistler 9212) were sandwiched along the handle centerline. The grip force was measured 

with these force sensors. Also, an accelerometer (PCB 339B24) was secured at the center point 

of the measuring cap to measure and control the vibration acceleration of the handles. 

The experiments were performed with one healthy male subject (aged 40 years). The subject was a nonsmoker and had never been exposed to high levels or long periods of hand-arm 

vibration occupationally or in his leisure time activities. The experiments were approved by the 

Research Ethics Committee of the Japan NIOSH. 

The vibration signal used in this study was a pseudorandom signal with a broadband 

spectrum ranging from 10 to 1250 Hz of a constant power spectrum density of 1.0 (m/s2

)

2

/Hz. 

We prepared two force coupling conditions: grip forces of 30 N and 50 N with a push force of 

0 N. For each force coupling condition, five trials were conducted. 

The subject posture used in this study was based on ISO 10819 requirements. The subject 

controlled the grip and feed forces under a certain force coupling condition by watching monitors 

during the measurement. 

Results and Discussion 

Figure 1 shows biodynamic response parameters measured with the same subject under 

the two different vibration systems. For each force coupling condition, the apparent mass and 

mechanical impedance obtained from biodynamic response measurements for the two vibration 

systems showed good agreement with each other. Differences of the apparent mass magnitudes 

observed in relatively low frequency ranges (<40 Hz) at the palm were statistically tolerable. Our 

15
 
 

 

 

results suggest that biodynamic response data obtained from the hand-arm vibration system at 

the Japan NIOSH can be comparable with data obtained from the system at the U.S. NIOSH. 

 

 

 

 

 

 

 

 

0 

(kg)

2.0 2.0 

1.5 

JPN (Finger) US (Finger) 

JPN (Palm) US (Palm) 

AM Magnitude 

AM Magnitude (kg) 

1.0 

0.5 

0.0
 

10 100 1000
 

0.0 

10 100 1000 

Frequency (Hz) Frequency (Hz) 

AM magnitude (grip force: 30 N) AM magnitude (grip force: 50 N) 

400 400 

1.5 

1.0 

0.5 

MI Magnitude (Ns/m) 300
 

200
 

100
 

0
 0
 

10 100 1000
 10 100 1000 

Frequency (Hz) Frequency (Hz) 

MI magnitude (grip force: 30 N) MI magnitude (grip force: 50 N) 

90 90 

60 60 MI Phase (deg) MI Magnitude (Ns/m) 300 

200 

100 

(deg) 30 MI Phase -30 

30 

0 

10 100 1000 

-30 10 100 

-60 -60 

-90 -90 

Frequency (Hz) Frequency (Hz) 

MI phase (grip force: 30 N) MI phase (grip force: 50 N) 

Figure 1.—Biodynamic response parameters given as functions of vibration frequency. (AM = apparent 

mass; MI = mechanical impedance). 

1000 

Acknowledgment: The authors are grateful to Ren Dong of NIOSH, Morgantown, WV, 

for his support to perform our experiments. 

References 

Dong RG, Welcome DE, McDowell TW, Wu JZ [2004]. Biodynamic response of human 

fingers in a power grip subjected to a random vibration. J Biomech Eng 126(4):447–457. 

ISO [1998]. Mechanical vibration and shock – Free, mechanical impedance of the human 

hand-arm system at the driving point. Geneva, Switzerland: International Organization for 

Standardization. ISO 10068:1998. 

16
 
 

SUSPENDED SEATS FOR REDUCING EXPOSURE TO WHOLE-BODY VIBRATION: 

IMPROVING STANDARD TESTS TO REDUCE INTERLABORATORY VARIATIONS 

Richard Stayner
 

RMS Vibration Test Laboratory, Ludlow, U.K.
 

Introduction 

­

­

Suspended seats are intended to reduce whole-body vibration transmitted from moving 

machines into the bodies of seated operators. The effectiveness of any particular seat suspension 

varies according to the application and operating conditions and depends on the frequency con

tent and magnitude of the input vibration. At its simplest, the system operator-suspension acts 

like a mass on a spring, so that it can attenuate input vibrations at frequencies higher than 2
 

times the system natural frequency. In reality, damper characteristics and friction effects make 

the system nonlinear so that performance changes with the magnitude of the input, and large 

excursions bring into play the suspension end-stops. This complicates the selection of a suspen

sion for a specific type of machine. Standard tests have been developed to overcome some of 

these difficulties. A critical part of these tests is to measure the vibration transmission of the seat 

for input vibration that is representative of the relevant machine type. The test codes specify the 

input vibrations and the weights of the operators (test persons). However, at least two attempts to 

conduct “round robin” tests among groups of European laboratories have shown differences of 

more than 25% in the measured performance of the same seats. CEN/TC231/WG9 (Seating), 

which is draft guidance on writing the test codes (EN 30326-1), is presently addressing ways to 

improve reproducibility, some of which are discussed below. 

Setting Up the Seat: Ride Height and Subject Posture 

With the help of the BGIA laboratory in Germany, WG9 ran a series of tests in which 

experienced test engineers from six laboratories measured the performance of two seats, each 

with an appropriate input vibration. For these tests, the engineers all used the same input vibra

tions and the same test persons. The “experimental variables” was the method used by each test 

engineer to determine the suspension height settings for the tests and the postures of the test per

sons. Surprisingly, in the worst case, the differences among test engineers exceeded 20%. From 

discussions with the engineers, a number of improvements to the guidance given in the test codes 

were suggested: 

•	 Specify a common way to measure the suspension travel and determine the midride 

position to be used for vibration measurement. 

•	 Display the suspension position continuously, first as an aid to correct setting, and 

then to allow corrections such as might be needed as the damper heats up. 

•	 Specify posture better, in particular, control the pressure under the thighs of the test 

person to limit vibration transmitted to the seat cushion through the legs. Specific 

instructions may also be needed to control muscle tone. 

•	 Specify test persons by sitting weight as opposed to standing weight. 

­

­

Controlling the Input Vibration 

In a second interlaboratory comparison, seven laboratories sent recordings of their input 

vibrations measured on the platform to an independent laboratory (IMMM, Slovak Republic) for 

comparison with the specifications, including tolerances on frequency spectra, and amplitude 

17
 
 

 

 

 

 

 

 

distributions. Again, there were some surprises. Some aspects of the specifications were clearly 

impractical and therefore were being ignored. In addition to correcting these points, the main 

advice was that the method of frequency analysis should be defined, i.e., common parameters 

should be used for fast Fourier transforms, such as sample rate (Δt), block length (Δf), time 

domain window, and amount of overlap. It should be noted that the differences found in both 

frequency and magnitude were small and were not experimentally correlated with any differences in measured vibration reduction. 

Replacing the Human Subject 

One obvious potential source of variation among laboratories is the difference in 

mechanical impedance (or apparent mass) of test persons, even when they have the same overall 

body mass. This, together with difficulties in finding very specific test persons, and aspects of 

subject safety have for years been behind attempts to replace live subjects with dummies. The 

frequency range of interest for suspended seats (vertical or z-axis suspension) extends from 

<1 Hz up to 20 Hz. The human body does not respond as a pure mass throughout all of that 

range; thus, many of the studies have been with dynamic dummies, starting with Suggs et al. 

[1969] and continuing up to the present with active models, e.g., Mozaffarin et al. [2007]. 

Nélisse et al. [2006] suggest that for applications with only very low-frequency components, 

a simple inert mass would make a quite suitable substitute for a live test person. This should be 

investigated further because it is easy to “calibrate” a mass. Passive spring-mass dummies could 

extend the frequency range and could be calibrated in a traceable way [Howard and Stayner 

1998], but difficulties have been found with controlling the damping elements. An active dummy 

can overcome this, but would be more difficult to calibrate in a process that allows traceability to 

primary standards. This aspect requires further work. 

Conclusions 

Gradual progress is being made toward reaching an acceptable reproducibility in testing 

suspended seats. Detailed guidance for test procedures is likely to help, but there are more steps 

to be made. Elimination of human test persons remains an outstanding goal. 

Acknowledgment: The author wishes to thank CVG KAB Seating for supporting this 

work. 

References 

EN 30326-1 [1994]. Mechanical vibration – laboratory method for evaluating vehicle seat 

vibration (ISO 10326-1:1992). Part 1: Basic requirements. 

Howard JC, Stayner RM [1998]. Dynamic dummies for seat testing: what the industry 

wants is a standard. In: 33rd U.K. Conference on Human Response to Vibration (Buxton, U.K.) 

Mozaffarin A, Pankoke S, Bersiner F, Cullmann A [2007]. MEMOSIK V: Development 

and application of an active, three-dimensional dummy for measurement of vibration comfort on 

vehicle seats. In: Proceedings of the Third National Conference on Human Vibration (Dresden, 

Germany, October 8–9, 2007). 

Nélisse H, Patra S, Boutin J, Boileau P-É, Rakheja S [2006]. Evaluation of two anthropodynamic manikins for seat testing under whole-body vibration. In: 41st U.K. Conference on 

Human Response to Vibration (Farnborough, U.K., September 20–22, 2006). 

Suggs CW, Abrams CF, Stikeleather LF [1969]. Application of a damped spring-mass 

human vibration simulator in vibration testing of vehicle seats. Ergonomics 12(1):79–93. 

18
 
 

 

 

MULTIAXIS SEAT CUSHION TRANSMISSIBILITY CHARACTERISTICS 

Suzanne D. Smith,1 and Jennifer G. Jurcsisn1 

1

Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 

 David R. Bowden,2

2

General Dynamics Advanced Information Systems, Dayton, OH 

Introduction 

The spectral characteristics of higher-frequency multiaxis military propeller aircraft 

vibration have been investigated [Smith et al. 2007]. The vibration properties of the coupled 

seat/cushion/human were further evaluated by applying a multiple-input/single-output model to 

estimate the system transfer matrix associated with exposure to multiaxis random vibration. 

Methods 

­

­

A U.S. Navy E-2C Hawkeye aircraft seat was tested with six cushion configurations and 

seven subjects in a multiaxis vibration facility. Cushion configurations A through E included five 

different seat pan cushions and the original seat back cushion with separate lumbar support. 

Cushion configuration F included the seat pan cushion used in E combined with a prototype seat 

back cushion. Triaxial accelerations were measured at the floor and on the left side of the seat 

near the base. Triaxial accelerometer pads measured the vibration between the human and cush

ions at the seat pan and seat back. Flat constant-bandwidth random vibration (1–80 Hz) was 

generated at 1.0 ms

−2 

rms to produce linearly independent combined-axis motions in the X, Y, 

and Z axes. The system transfer matrix is written as: 

−1

⎡H
 ⎤ ⎡ ⎤ xO s s s
 ⎢ xx xy xz ⎡S
 ⎤ ⎢ ⎥ ⎥ xO ⎢ ⎥ =
 (1)
 ⎢

H
 yO ⎥ ⎢s yx s yy s
 yz ⎥ ⎢

S
yO ⎥ ⎢H
 ⎥ ⎢ ⎥ ⎢ ⎥ ⎣ zO ⎦ ⎣szx szy s
 zz ⎦ ⎣S
zO ⎦

where HxO, HyO, and HzO represent the transfer functions (transmissibilities) between a single out

put, O, and inputs x, y, and z at the floor (ω not shown in Equation 1); sxx, sxy,...szz are the autoand cross-spectra between the input signals; and SxO, SyO, and SzO are the cross-spectra between 

the three inputs at the floor and the output, O. The output, O, was measured in the X, Y, and Z 

directions at the seat pan, seat back, and seat base. 

Results 

Figure 1 illustrates the mean multiaxis transmissibilities for the major responses at the 

seat pan and seat back. All cushions tended to show a small amplification of the seat pan X/x, 

seat pan Z/z, and seat back X/x vibration in the vicinity of whole-body vertical resonance 

(4–8 Hz). The seat pan, seat back, and seat base showed a substantial peak in the Y/y transmissibility between 12 and 15 Hz. This peak was also observed in the seat back X/x transmissibility, 

but at a lower magnitude. All cushions showed increases in the seat base and seat pan X/x, Z/z, 

and X/z transmissibilities over a broad range between 30–50 Hz (Figure 1). This increase was 

also observed for the seat back Z/z. Higher seat pan X/x and seat pan X/z transmissibilities were 

observed at higher frequencies (>70 Hz). Cushion F showed significant damping in the higherfrequency seat back X/x and seat back X/z transmissibilities (Figure 1). 

19
 
 

 

 

 

 

 

TRANSMISSIBILITY TRANSMISSIBILITY 5.0 SEAT PAN X/x Cushion A SEAT PAN Y/y Cushion A Cushion A Cushion A Cushion D SEAT PAN Z/z Cushion B Cushion B Cushion B Cushion B Cushion E 

Cushion C Cushion F 

Cushion D 4.0 Cushion C Cushion C Cushion C 

Cushion D Cushion D Cushion E Cushion E Cushion E 

3.0 Cushion F Cushion F Cushion F 

2.0 

1.0 

SEAT PAN X/z 0.0 

0	 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 

FREQUENCY (Hz) 

5.0 Cushion A Cushion A 

Cushion B 

SEAT BACK X/x Cushion A SEAT BACK Y/y SEAT BACK Z/z Cushion A SEAT BACK X/z Cushion B Cushion B Cushion B 

Cushion C Cushion C 

Cushion D 

4.0 Cushion C Cushion C 

Cushion D Cushion D 

Cushion E 

Cushion D 

Cushion E Cushion E Cushion E 

3.0 Cushion F Cushion F Cushion F Cushion F 

2.0 

1.0 

0.0 

0 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 

FREQUENCY (Hz) 

Figure 1.—Mean seat pan and seat back transmissibilities (seven subjects). 

Discussion 

­

­

The operational exposures [Smith et al. 2007] showed that the older original seat pan 

cushion (cushion A) produced significantly higher seat pan accelerations in the X direction at the 

blade passage frequency (BPF ~73.5 Hz) compared to the other tested cushions. This was pre

dicted by the transmissibility data: cushion A produced significantly higher seat pan X/x trans

missibility compared to cushions B and C (Figure 2) and produced significantly higher seat pan 

X/z transmissibility compared to all other cushions.

 

 

5.0 5.0 

TRANSMISSIBILITY 4.0 

3.0 

2.0 

1.0 

SEAT PAN X/x 73.5 Hz 

TRANSMISSIBILITY 

SEAT PAN X/z 73.5 Hz 

4.0 

3.0 

2.0 

1.0 

0.0 0.0 

A B C D E 

CUSHIONS 

F A 

CUSHIONS 

B C D E F 

Figure 2.—Seat pan X/x and X/z transmissibility at 73.5 Hz. 

 The z-axis vibration may have the greatest 

influence on the higher-frequency X-axis seat pan vibration; the X/z transmissibilities were 

higher compared to X/x. However, the input vibration at the BPF was the highest in the X direction. The damping effect of the prototype seat back cushion (cushion F) was also observed at the 

BPF. The seat base transmissibility 

results did indicate that the E-2C seat 

structure was not rigid, particularly in the
 

Y axis, and most likely influenced the 

behavior at the seat/occupant interfaces. 

The transmissibility data can be used to 

predict the multiaxis accelerations entering the human during operational exposures and target seat vibration mitigation 

strategies. 

Reference 

Smith SD, Jurcsisn JG, Walker AY, Smith JA, Bowden DR [2007]. Dynamic characteristics and human perception of vibration aboard a military propeller aircraft. Wright-Patterson 

Air Force Base, OH: Air Force Research Laboratory, Human Effectiveness Directorate, 

Biosciences and Protection Division, Biomechanics Branch. Report No. AFRL-HE-WP-TR2007-0114. NTIS No. ADA473700. 

20
 
 

 

 

 

 

 

 

 

 

 

 

COMPARISON OF THE PERFORMANCE OF A PNEUMATIC ACTIVE SEAT
 

SUSPENSION USING A DISCRETE AND FUZZY LOGIC-BASED CONTROL LAW
 

Bertrand Valero,1

 Farid Amirouche,1

1

Vehicle Technology Laboratory, University of Illinois at Chicago (UIC)
 

 and Alan G. Mayton2 

2

National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, 


Pittsburgh, PA
 

Introduction 

The torque generated by a heavy vehicle engine can lead to a high level of vibration 

inside the operator’s cabin. It raises not only safety issues concerning the operator’s ability to 

perform his or her task, but also health issues. Indeed, prolonged exposure to such vibration 

has been linked to an increase in the risk of lower back problems and other illnesses [Schwarze 

et al. 1998]. 

The addition of a suspension system between the operator’s seat and the chassis of the 

vehicle lowers the level of vibration felt by the driver. Passive suspension designs have been 

introduced but have limitations. The skyhook control method [Karnopp et al. 1974] was used in 

this study, which investigated an active seat suspension under various conditions. The main idea 

behind the active suspension design is to introduce an actuator and adjust its damping properties 

depending on input signals from sensors placed on the seat and chassis of the vehicle [Valero 

et al. 2007]. 

The damping of the actuator can be set at different levels chosen from a predetermined 

set of configurations for the actuator [Valero et al. 2006]. The nonlinearity introduced by such an 

approach can lead to chattering due to the high-frequency switching in the actuator command. 

To achieve more linear behavior in the actuator, a control method using fuzzy logic concepts 

[Guglielmino et al. 2005] was implemented, with an active pneumatic suspension design developed at the UIC Vehicle Technology Laboratory. 

Methods 

The suspension system was tested at the National Institute for Occupational Safety and 

Health’s Pittsburgh Research Laboratory. The suspension was bolted to an MTS shake table, and 

a mass of 40 kg was bolted to the top of the suspension system. The test protocol consisted of a 

sinusoidal vibration sweep of amplitude ±10 mm or ±20 mm and a frequency range of 1–8 Hz at 

0.1-Hz intervals. The signals from two accelerometers placed on top of the suspension and onto 

the chassis were used as input by a control algorithm that returns a position for the valve using 

the fuzzy logic approach. Different variations of the control laws were tested by changing the 

number of membership functions for the fuzzy logic implementation. The pressure inside the 

actuator of the pneumatic suspension was also set to different levels. During a previous test session, the same testing protocol, suspension design, and conditions were used to evaluate the 

performance of the suspension. The only difference was the control method used; it included a 

discrete number of damping levels for the actuator. Subsequently, the efficiency of the fuzzy 

logic approach can be evaluated by comparing the results obtained during the two testing sessions. 

Results 

In both cases, when actuator pressure was increased, the results showed a reduction of the 

peak amplitude at the resonant frequency for all of the control strategies. The discrete approach 

showed a direct correlation between the resonance peak and the ability to select higher damping 

21
 
 

 

 

options using different valve positions. In the fuzzy logic approach, we observed better isolation 

at the resonant frequency when the number of membership functions considered in the control 

method was reduced. Of the two control approaches, the fuzzy logic approach showed better 

performance. 

Figure 1.—Experimental setup. 

 

60 PSI 

0 

0.5 

1 

1.5 

2 

2.5 

0 1 2 3 4 5 6 

frequency 

transm issibility

4 fuzzy 

3 fuzzy 

2 fuzzy 

Figure 2.—Transmissibility of the seat with a fuzzy controller (left) and a discrete controller (right). 

References 

Guglielmino E, Stammers CW, Stancioiu D, Sireteanu T, Ghigliazza R [2005]. Hybrid variable structure-fuzzy control of a magnetorheological damper for a seat suspension. Int J Vehicle 

Autonomous Syst 3(1):34–46. 

Karnopp DC, Crosby MJ, Harwood RA [1974]. Vibration control using semi-active force 

generators. ASME J Eng Ind 96(2):619–626. 

Schwarze S, Notbohm G, Dupuis H, Hartung E [1998]. Dose-response relationships 

between whole-body vibration and lumbar disk disease: a field study on 388 drivers of different 

vehicles. J Sound Vibration 215(4):613–628. 

Valero B, Amirouche FML, Mayton AG [2006]. Pneumatic active suspension design for 

heavy vehicle seats and operator ride comfort. In: Proceedings of the First American Conference on 

Human Vibration (June 5–7, 2006). Morgantown, WV: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2006–140, pp. 38–39. 

Valero B, Amirouche FML, Mayton AG, Jobes CC [2007]. Comparison of passive seat suspension with different configuration of seat pads and active seat suspension. Warrendale, PA: Society 

of Automotive Engineers, Inc., technical paper 2007-01-0350. 

22
 
 

 

 

 

 

 

CHARACTERIZATION OF THE NOISE AND VIBRATION PRODUCED BY
 

PORTABLE POWER TOOLS USED IN THE AUTOMOTIVE REPAIR INDUSTRY
 

Pierre Marcotte,1 Jérôme Boutin,1

 and Hugues Nélisse1 

1

Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), 


Montreal, Quebec, Canada
 

 Rémy Oddo,2 

2

Acoustics Group, University of Sherbrooke, Sherbrooke, Quebec, Canada
 

Introduction 

Users of handheld power tools can be exposed to excessive levels of noise and hand-arm 

vibration. The current ISO standards used to evaluate the vibration and noise levels of these tools 

generally do not take into account the interaction between the tool and the worked piece. However, this interaction is important since, in some cases, the noise and vibration generated by these 

tools is strongly dependent upon the tool-worked piece interaction. Thus, the goal of this study 

was to develop new test benches that include the tool-worked piece interaction. 

Methods 

Test benches based on existing standards were used to measure the noise and vibration 

levels of three categories of handheld power tools currently used in auto repair shops and 

recognized as being potentially problematic in terms of noise exposure and hand-arm vibration. 

They consist of pneumatic wrenches, impact wrenches, and die grinders. They were tested 

according to the ISO 8662-7 and ISO 8662-13 standards to assess their vibration levels and to the 

ISO 15744 standard to assess their noise levels. ISO 8662-7 describes the operation of pneumatic 

and impact wrenches in a resistive setup at a constant rpm, while ISO 8662-13 describes the 

operation of die grinders with an artificial eccentric bit. In an additional step, the test benches 

were modified in order to include the interaction between the tool and the worked piece, thus 

better representing the operation of these tools in a real work environment. For the pneumatic 

wrenches and impact wrenches, the second-generation test bench consisted of screwing nuts on 

threaded rods, while for the die grinder, the second-generation test bench consisted of grinding, 

sanding, and cleaning a standardized piece of steel with a metal brush. Measurements of noise 

and hand-arm vibration upon various handheld power tools were also carried out in several 

garages in order to guide the development of these second-generation test benches. 

Results 

A summary of the noise and vibration levels obtained with the first- and secondgeneration test benches is shown in Table 1 for four different pneumatic wrenches. The vibration 

levels are higher with the first-generation test benches for all tested tools, while the sound power 

levels are similar between the two generation test benches. The results obtained with five different impact wrenches are shown in Table 2. For the impact wrenches, the vibration levels 

obtained with the two generation test benches are similar, while the sound power level is 4.6– 

7.2 dB(A) lower with the second-generation test benches. Table 3 shows a summary of the noise 

and vibration levels for four different die grinders using the first- and second-generation test 

benches. The levels reported for the second-generation test bench consist of the maximum values 

obtained from the three tasks (grinding, sanding, and cleaning). The results show similar sound 

power levels for all tested tools, but the vibration levels are much greater with the secondgeneration test bench. 

23
 
Table 1.—Summary of laboratory measurements on pneumatic wrenches 

2 Vibration (m/s , W h)Sound power (L w,dB(A)) Capacity Manufacturer Model 1st 2nd 1st 2nd (Nm) generation generation generation generation 

A 1 68 12.54 4.48 102.9 101.8 

B 3 81 NA 5.67 NA 94.5

B 2 68 8.355.32 100.3 100.2 

C 4 75 5.244.05 98.3 98.7

Table 2.—Summary of laboratory measurements on impact wrenches 

Manufacturer Model Capacity 

(Nm) 

2 Vibration (m/s , W h) Sound power (L w,dB(A)) 

1st 

generation 

2nd 

generation 

1st 

generation 

2nd 

generation 

A 1 949 6.89 6.46 107.2 100.0 

A 2 949 6.93 5.08 101.0 95.6

B 3 847 6.59 5.39 103.1 98.5

B 4 576 4.01 3.83 103.9 96.7

C 5 576 5.49 5.05 106.1 99.0

Table 3.—Summary of laboratory measurements on die grinders 

Manufacturer Model 

2 Vibration (m/s , W h)Sound power (L w,dB(A)) 

1st 2nd 1st 2nd 

generation generation generation generation 

B 1 6.15 14.59 95.6 97.8

B 2 5.68 9.61104.2 103.8 

C 3 3.55 10.19 104.2 104.5 

A 4 7.59 10.02 NA 100.3 

 

 

 

Discussion 

The results from the second-generation test benches show lower noise levels for impact 

wrenches, lower vibration levels for pneumatic wrenches, and higher vibration levels for die 

grinders. However, paired t-tests indicate that the differences in the vibration levels of the impact 

wrenches between the two generations are not statistically significant (α = 0.05). Thus, new ISO 

test benches should include the interaction of the tool with the worked piece in assessing vibration levels of pneumatic wrenches and die grinders and noise levels of impact wrenches. 

References 

ISO [1997a]. Hand-held portable power tools – Measurement of vibrations at the handle – 

Part 7: Wrenches, screwdrivers and nut runners with impact, impulse or ratchet action. Geneva, 

Switzerland: International Organization for Standardization. ISO 8662-7:1997. 

ISO [1997b]. Hand-held portable power tools – Measurement of vibrations at the handle – 

Part 13: Die grinders. Geneva, Switzerland: International Organization for Standardization. 

ISO 8662-13:1997. 

ISO [2002]. Hand-held non-electric power tools – Noise measurement code – Engineering method (grade 2). Geneva, Switzerland: International Organization for Standardization. 

ISO 15744:2002. 

24
 
Session III: Whole-Body Vibration I 

Chair: Subhash Rakheja * 

* Author unable to attend conference.
 

25
 

Co-Chair: N. Shibata 

Presenter 

A. G. Mayton 

National Institute for 

Occupational Safety and 

Health (NIOSH) 

Title 

Assessment of Whole-Body Vibration Exposure 

on Haulage Trucks and Front-end Loaders at 

U.S. Aggregate Stone Operations 

Page 

26 

M. S. Contratto 

Caterpillar, Inc. 

Evaluation of Vibration Exposure of Operators in Wheel 

Tractor-Scrapers 

28 

S. Pankoke 

Wölfel 

Static and Dynamic Properties of Polyurethane Foams for 

Mobile Machine Static Seats and Their Effects on 

Operator Exposure to Whole-Body Vibration 

30 

H. W. Paschold 

Ohio University 

Pilot Study of Whole-Body Vibration in Fully Automated 

Residential Solid Waste Collection 

32 

B. Bazrgari 

École Polytechnique 

Biodynamics of the Human Trunk in Seated Whole-Body 

Vibration 

34 
 

 

 

 

 

 

 

 

ASSESSMENT OF WHOLE-BODY VIBRATION EXPOSURE ON HAULAGE TRUCKS 

AND FRONT-END LOADERS AT U.S. AGGREGATE STONE OPERATIONS 

Alan G. Mayton,1 and Christopher C. Jobes1 

1

National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, 


Pittsburgh, PA
 

Richard E. Miller,2

2

National Institute for Occupational Safety and Health, Spokane Research Laboratory,
 

Spokane, WA
 

Introduction 

Preliminary vibration data were obtained during a study conducted at two eastern quarries 

of a major U.S. aggregate stone producer. As a result of employee feedback concerning low back 

discomfort and bouncing/jarring, company management decided to evaluate seating and operator 

whole-body vibration (WBV) exposure at two quarries for drivers/operators on haulage trucks 

and front-end loaders. Two study hypotheses were presented: (1) older equipment at quarry 1 

would show worse WBV exposure results than the newer haulage/loading machinery at quarry 2; 

(2) measurements of WBV exposure would support employee complaints of musculoskeletal 

symptoms, particularly for the low back, during haulage truck and front-end loader operation. 

Quarry 2 operated with newer model equipment with greater hauling and loading capacity than quarry 1. All of the haulage trucks were rear-dump style, and the haulage trucks and 

their respective seats were in good working order. The travel routes and drivers were different 

between the two quarries. The roadways were dusty and required constant watering for dust 

abatement during data collection at quarry 1, whereas a steady rain caused wet conditions during 

1 of 2 days of data collection at quarry 2. Data were collected on one pit front-end loader at 

quarry 1 and one pit and one plant/yard loader at quarry 2. 

Methods 

Vibration data were collected using PCB Piezotronics (Depew, NY) triaxial accelerometers (models 356B18, 356B40) with signal amplifiers (model 480E09) and filters (150-Hz lowpass, model 474M32) connected to a Sony digital data recorder (model PC208Ax, Sony Manufacturing Systems America, Lake Forest, CA). The mean sampling time for quarry 1 was 21 min 

(standard deviation (SD) = 13 min); mean sampling time for quarry 2 was 63 min (SD = 24 min). 

These were considered representative of exposures for the shift. WBV exposures for vehicle 

drivers/operators were assessed relative to ISO 2631-1 (1997) and the European Union Good 

Practice Guide for WBV [Griffin et al. 2006]. 

Results and Discussion 

Table 1 describes the equipment operating at quarries 1 and 2 and shows the results from 

WBV exposure measurements collected for haulage trucks and front-end loaders. Weighted 

RMS accelerations (wRMS) and vibration dose values (VDVs) for the dominant axis of vibration 

and overall weighted total RMS accelerations (vector sums) were computed for comparison. 

In five of six trials for quarry 1 haulage trucks, wRMSz exceeded the action level 

(0.5 m/s2

) recommended in the European Union Good Practice Guide for WBV [Griffin et al. 

2006]. By contrast, in one of three trials for haulage trucks at quarry 2, wRMSz just barely 

26
 
 

 

 

exceeded this same action level. No haulage trucks at either quarry showed VDVz that reached 

the 9.1 m/s1.75 action level. Vector sums may indicate driver/operator discomfort or a “rougher” 

ride (ISO 2631-1 (1997)). For the older trucks at quarry 1, vector sums varied from 0.64 to 

2.73 m/s2

 with a mean of 1.58 m/s2 and 0.87 m/s2 SD. Vector sums for quarry 2 haulage trucks 

exhibited less variation, ranging from 0.42 to 0.61 m/s2 with a mean of 0.51 m/s2 and 0.10 m/s2 

SD. In contrast to the quarry 1 pit front-end loader, the newer and larger-capacity pit loader at 

quarry 2 showed wRMSx at 1.21 m/s2, exceeding both action and exposure levels specified in the 

European Union Good Practice Guide for WBV [Griffin et al. 2006]; VDVx at 12.26 m/s1.75 

exceeded the action level. In comparing the mean wRMSz and vector sum accelerations in this 

study with Eger et al. [2006], quarry 2 haulage trucks were slightly higher, but the quarry 1 

trucks were more than three to four times higher. In summary, the two hypotheses stated earlier 

seem true in view of the findings, although more data are needed to verify this. 

­

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1.—Description of equipment with weighted RMS accelerations, vector sums, and vibration dose values 

(shading indicates dominant axis) 

Mobile 

equipment 

Manu

facturer Year Capacity wRMSx 

(m/s2) 

wRMSy 

(m/s2) 

wRMSz 

(m/s2) 

Vector 

sum 

(m/s2

) 

Overall 

VDV 

(m/s1.75) 

VDVx 

(m/s1.75) 

VDVy 

(m/s1.75) 

VDVz 

(m/s1.75) 

Quarry No. 1 

Haulage 

truck 

A 1986 50.8 mt 0.48 0.56 1.00 1.15 5.21 1.97 2.06 4.36 

0.28 0.25 0.46 0.64 2.91 1.47 1.01 2.25 

A 1978 50.8 mt 0.73 0.74 1.83 2.73 8.28 3.07 3.31 6.94 

0.28 0.34 0.60 0.96 3.04 1.21 1.42 2.40 

A 1986 50.8 mt 0.45 0.48 0.98 1.40 4.86 1.80 1.80 4.15 

0.91 1.08 1.68 2.57 8.63 3.59 4.13 6.67 

Front-end 

loader B 1997 6.3 m3 0.30 0.43 0.41 0.66 3.31 1.64 1.93 2.13 

Quarry No. 2 

Haulage 

truck 

C 2000 66.0 mt 0.25 0.27 0.51 0.49 8.98 3.26 3.25 7.71 

C 1999 66.0 mt 0.25 0.26 0.41 0.42 6.55 3.23 3.14 4.75 

B 2000 71.1 mt 0.30 0.37 0.43 0.61 7.27 3.33 4.17 4.94 

Front-end 

loader 

B 2005 10.7 m3 1.21 1.02 0.75 1.24 17.58 12.26 10.30 7.27 

C 2000 5.4 m3 0.32 0.28 0.36 0.36 6.19 3.80 2.97 3.87 

References 

Eger T, Salmoni A, Cann A, Jack R [2006]. Whole-body vibration exposure experienced 

by mining equipment operators. Occup Ergon 6(3/4):121–127. 

Griffin MJ, Howarth HVC, Pitts PM, Fischer S, Kaulbars U, Donati PM, Bereton PF 

[2006]. Guide to good practice on whole-body vibration: non-binding guide to good practice 

with a view to implementation of directive 2002/44/EC on the minimum health and safety 

requirements regarding the exposure of workers to the risks arising from physical agents 

(vibrations). [http://www.humanvibration.com/EU/VIBGUIDE/ 

WBV%20Good%20practice%20Guide%20v6.7g%20English%20070606.pdf]. Date accessed: 

May 2008. 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

27
 
 

 

 

EVALUATION OF VIBRATION EXPOSURE OF OPERATORS
 

IN WHEEL TRACTOR-SCRAPERS
 

Michael S. Contratto and Jinyan (Christy) Du
 

Caterpillar, Inc., Peoria, IL
 

Introduction 

Due to uncertain knowledge of human responses to vibration, both objective vibration 

measurements and subjective scaling are used to evaluate the vibration level to which machine 

operators are exposed. This study seeks to develop a model to describe the operator’s perceived 

discomfort as a function of the measured acceleration so that vibration comfort level can be 

predicted by the acceleration measurements. This was done by (1) identifying the vibration 

measurement that seems to be the best correlation with subjective response, (2) investigating 

effects caused by different experimental design variables on subjective response and vibration 

acceleration, and (3) using linear regression to model the relationship between the selected vibration measurement and the subjective response. 

Methods 

Nine operators were selected to run a wheel tractor-scraper passing over a bump. Four 

variables were investigated, including two bump heights, two load conditions (empty and full), 

left or right tire crossing over the bump, and five speed levels. Acceleration was measured at the 

seat base and seat pad using triaxis accelerometers with a sampling rate of 500 Hz. In order to 

identify which frequency weighting and analysis method gave the best correlation with subjective rating, four frequency-weighted filters were applied on the raw measurement: ISO, ISOM 

(modification to ISO 2631 weight curves), jerk, and 12 Hz (Figure 1). 

Frequency Weighting Curves

Vertical

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8 10 12 14 16 18 20

Frequency (Hertz)

Weighting

12 Hz ISOM

ISO

Jerk

 Frequency Weighting Curves

F/A S/S

0

0.2

0.4

0.6

0.8

1

1.2

0 2 4 6 8 10 12 14 16 18 20

Frequency (Hertz)

Weighting

12 Hz ISO

ISOM

Jerk

 

 

 

Frequency Weighting Curves 

Vertical 

0 

0.2 

0.4 

0.6 

0.8 

1 

1.2 

0 2 4 6 8 10 12 14 16 18 20 

Frequency (Hertz) 

Weighting 

12 Hz ISOM 

ISO 

Jerk 

Frequency Weighting Curves 

F/A S/S 

0 

0.2 

0.4 

0.6 

0.8 

1 

1.2 

0 2 4 6 8 10 12 14 16 18 20 

Frequency (Hertz) 

Weighting

12 Hz ISO 

ISOM 

Jerk 

Figure 1.—Frequency weighting curves. (F/A = fore/aft; S/S = side/side.) 

For each filter, the minimum, maximum, range, root-mean-square (RMS), vibration dose value 

(VDV), and maximum transient (x,y,z), maximum of the RMS value of three vectors (x,y,z), and 

the vector sum RMS were calculated. A 1–9 rating scale was used to determine the operators’ 

subjective assessment of vibration comfort. 

Results 

Statistic analysis was performed using Minitab. Analyses of Pearson’s correlation test 

showed measurements from the seat pad had higher correlation with the subjective measurements than those from the seat base. The correlation coefficients with all four frequency28
 
weighted filters were similar. The highest correlation coefficients were around 0.68–0.7 with 

vector sum RMS, maximum RMS (x,y,z), VDV, and maximum transient vibration value 

(MTVV). Jerk data showed slightly higher correlation than others. Also, smaller deviations were 

shown in the vector sum RMS and maximum RMS (x,y,z) than in the VDV and MTVV; therefore, the jerk vector sum RMS data were selected for further statistical analysis. 

Analysis of the main effects demonstrated that speed, bump height, and the tire passing 

over the bump have significant effects on both acceleration measurements and subjective 

response (P-value < 0.001). A regression model based on the group average of each test run 

showed a significant relationship between the jerk vector sum RMS and operator subjective 

rating, while the regression model of the individual data showed large variation between the 

vibration measurements and the subjective rating (R2 = 48%) (Figure 2). 

3

Scatterplot of MeanSub vs MeanRMS Regression of Group Average Regression of Individual Data 

1,6,4,R 8

0,6,4,R 

5 0,5,4,R 1,5,4,R 7

0,5,4,L 1,6,4,L 

6

1,5,4,L 0,6,4,L 

4 1,4,4 R0,4,4,R 5

MeanSub

SUB_RAT

0,4,4,L 1,4,4,L 4

3

0,3,4,L 1,3,4,L 1,3,4,R 1,5,2,R 

1,6,2,R 

0,5,2,R 0,3,4,R 1,6,2,L0,6,2,R 1,2,4,R 0,2,4,L 0,2,4,R 2 0,5,2,L0,6,2,L 1,5,2,L1,4,2,R 1,2,4,L 0,4,2,R 1 1,4,2,L 2 1,3 2 R1,,3,,2,L
 

1,2,2,R 0,3,2,L 0,4,2,L
 1,2,2,L 0,3,2,R 0

­1

1

0 10 20 30 40 50 60 70

0, ,2,R0,2, 22,L 

10 20 30 40 50 60 70
 

Base JERK sum S Jerk RRMMS 

Figure 2.—Regression of group average and individual measurements. 

MeanRMS

 Normalizing the subjective rating data helped 

increase the correlation with the acceleration measurement (r = 0.785). The regression model using the 

normalized subjective data was also better than using 

the nonnormalized data (R2 = 62%) (Figure 3). 

12

Normalize = 2.547 + 0.117

Jerk RMS 9

Normalize

6

3

0

0 10 20 30 40 50 60 70

Base sum Jerk MS Jerk RMS 

Figure 3.—Regression model of normalized

rating and the RMS value. 

How

ever, due to the high operator-to-operator variation even 

with normalized data, the upper boundary of the data set 

was used as the linear regression function to predict the 

comfort level using the acceleration measurements. 

Discussion 

 

 This study concluded that the difference 

between frequency weightings is not significant. 

Because the variance of the subjective response to 

comfort level is large, the correlation between the subjective response and acceleration 

measurement is not very good. The variance also affects the accuracy of the regression model. 

Normalization does help decrease variation of the subjective scaling data, but improvement is not 

significant. 

­

29 
 

 

STATIC AND DYNAMIC PROPERTIES OF POLYURETHANE FOAMS FOR MOBILE
 

MACHINE STATIC SEATS AND THEIR EFFECTS ON OPERATOR EXPOSURE
 

TO WHOLE-BODY VIBRATION
 

S. Pankoke,1 and J. Hofmann1 

1

Wölfel Beratende Ingenieure GmbH + Co. KG, Höchberg, Germany 

M. S. Contratto,2 A. Striegel,2

2

Caterpillar, Inc., Peoria, IL 

Introduction 

Seat cushions have a dramatic impact on both the ride experienced by the operator and 

the operator’s subjective opinion of the machine ride. Static seats for mobile machines and 

commercial vehicles, i.e., seats that do not have an explicit spring and damper suspension, may 

provide isolation of the operator from vibrations only by the stiffness and damping properties of 

the polyurethane foams. It is desirable to analyze the effect of foam properties on vibration isolation behavior when used in a static seat with a human. 

Methods 

Polyurethane foams are investigated by static and dynamic compression tests of quadshaped foam samples. A hydraulic test rig compresses the samples between two rigid plates 

(Figure 1).

 Figure1.—Hydraulic test rig with foam. 

Compression (mm) and compression force (N) are measured and evaluated. From the 

raw data, static hysteresis plots and plots of the frequency-dependent complex Young’s Modulus 

are computed. The data are then used for the identification of material models for a dynamic 

finite-element simulation using Abaqus and the dynamic occupant model CASIMIR in configu

ration m50 (1.75-m body height, 75-kg body mass) [Pankoke and Siefert 2006]. 

With such identified material models for the polyurethane foams, a simplified model of 

the occupied seat is set up. The seat is modeled with a quad-shaped foam cushion and backrest; 

the seat and back are considered to be rigid. The dynamic occupant model, CASIMIR configura

­

­

30
 

tion m50, represents the operator (Figure 2).

 Figure2.—Simplified seat with CASIMIR. 

 The sitting posture of CASIMIR is adapted to typical seat and backrest angles of operator seats. 

With this model, a static seating simulation is performed to find the appropriate operating 

point for the succeeding dynamic simulation. The dynamic simulation is carried out in the frequency domain from 0.5 to 15 Hz, using vertical (z) excitation at the cushion base. 
 

 

 

 

 

 

 

 

Results 


Results from the static material tests show the typical S-shaped hysteresis curves of poly ­

urethane foams (Figure 3).

Figure 3.—Static hysteresis with identification. 

 Differences occur between loading and unloading, building the 

hysteresis. For the static material model, the average between loading and unloading is used as 

identification target. Identification results are very close to this target. 

The dynamic material model is based on the complex Young’s modulus, which depends 

on the polyurethane material (Figure 4), static precompression, frequency, and the dynamic 

vibration magnitude. 

Figure 4.—Complex Young’s modulus. 

­

Differences in dynamic foam characteristics result in differences in the isolation behavior 

of the foams as expressed by the vertical seat transfer function HS (s), defined as the complex 

ratio between the vertical vibration response Q(s) on the cushion surface and the vertical vibra

tion excitation Q0

(s) at the seat base (s = iQ is the Laplace variable): HS (s) = Q(s) / 0 Q (s). 

Figure 5 shows the differences in HS (s). 

Figure 5.—Seat transfer functions HS (s)


for different foams.
 

Discussion 

With the above results for HS (s) for different 

foams, it is now possible to identify the best cushion 

property to minimize operator vibrations. It is 

foreseeable that this will depend on the machine type, 

since different machines have different typical excitation 

spectra at the seat base. The identification of the best 

foam for different machine types (wheel loaders, tractor 

scrapers, track-type tractors) will be the next step in 

this study. 

Reference 

Pankoke S, Siefert A [2006]. Simulation of human motion, muscle forces, and lumbar spine 

stresses due to whole-body vibration: application of the dynamic human model CASIMIR for the 

development of commercial vehicles and passenger cars. In: Proceedings of the First American Conference on Human Vibration (June 5–7, 2006). Morgantown, WV: U.S. Department of Health and 

Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2006–140, pp. 46–47. 

31
 

 

 

PILOT STUDY OF WHOLE-BODY VIBRATION
 

IN FULLY AUTOMATED RESIDENTIAL SOLID WASTE COLLECTION
 

Helmut W. Paschold
 

School of Health Sciences, Ohio University, Athens, OH
 

Introduction 

­

­

­

Residential solid waste collection methods range from manual to semiautomated to auto

mated loading. Manual loading is accomplished by a crew physically moving and dumping waste 

containers into hoppers of trucks. Semiautomated systems require manual movement and place

ment of the waste containers at the truck hopper so a hydraulic or mechanical device can lift and 

empty the waste containers. In a fully automated system, a driver collects solid waste from con

tainers using a joystick-controlled robotic arm, without leaving the vehicle cab. Full automation 

eliminates safety and health hazards resulting from manual lifting, walking, and direct contact 

with the solid waste, leading solid waste collection management to believe that most job risks 

have been eliminated. However, two new hazard exposures were introduced with the automated 

system: joystick manipulation and whole-body vibration (WBV). 

Several studies have evaluated solid waste collection trucks and WBV. Maeda and 

Morioka [1998] reported vibration exposure exceeding ISO 2631 recommended limits in the 

mode of manual collection. With semiautomated collection, Melo and Carvalhinho [2006] 

reported WBV doses exceeding the action value in 5 of 13 garbage trucks, while Bovenzi et al. 

[2006] found WBV levels below the action value in 6 trucks. 

In the automated method, the driver positions the truck in approximate alignment with the 

container and extends a robotic arm. This arm grasps, lifts, and dumps the filled container into a 

hopper at the top of the truck (see Figure 1).

Figure 1.—Automated collection truck (left) with a closeup of the robotic arm (right). 

 Automated operators are exposed to the vibrations 

from the robotic arm lifter. Also, it seems that the automated vehicles tend to have more stops 

and starts as the driver aligns with each individual container. 

Methods 

During the summer of 2007, vibration measurements were made in a total of four vehicles during a 2-day period. WBV measurements were obtained with Quest Technologies (QT) 

HAVPro human vibration meters with QT seat pad triaxial accelerometers. The data buffers 

recorded a series of 24 consecutive 20-min sets, equivalent to a full workday in a residential 

urban neighborhood on relatively flat, well-paved streets. 

32
 
 

 

 

 

 

Results and Discussion 

The data in Table 1 and Figure 2 are representative of other WBV values for collection 

activity obtained in this pilot study.

Figure 2.—Results of one 20-min period during residential solid waste collection. 

Table 1.—Tabular results from Figure 2 2 (m/s ) 

X Y Z Sum 

Amin 

Amax 

A(8) 

0.0166 

1.0095 

0.4120 

0.0151 

0.8986 

0.5123 

0.0879 

0.8734 

0.5542 

— 

— 

1.0744 

 Lower levels were found during travel, idle time, and landfill 

transport. The higher values of this study in the horizontal (x and y) axes, when compared with 

those previously reported for solid waste truck operation, may be explained by the robotic arm 

activity or increased vehicle starts and stops. Additional data analysis is being performed to 

evaluate the combined daily data set for an accurate daily exposure value. This pilot study 

identifies a need to obtain improved operation mode detail from the operator or an assigned 

observer. Additional variables to consider in future studies include the effects of collection route 

characteristics (terrain, roads, home spacing), equipment type, robotic arm operation, and seat 

transmission. 

References 

Bovenzi M, Rui F, Negro C, D’Agostin F, Angotzi G, Bianchi S, Bramanti L, Festa G, 

Gatti S, Pinto I, Rondina L, Stacchini N [2006]. An epidemiological study of low back pain in 

professional drivers. J Sound Vibration 298(3):514–539. 

Maeda S, Morioka M [1998]. Measurement of whole-body vibration exposure from garbage trucks. J Sound Vibration 215(4):959–964. 

Melo RB, Carvalhinho F [2006]. Whole-body vibration exposure of waste truck drivers. 

In: Proceedings of the 16th World Congress of the International Ergonomics Association (Maastricht, Netherlands, July 10–14, 2006). Elsevier. 

33
 
 

 

 

 

BIODYNAMICS OF THE HUMAN TRUNK IN SEATED WHOLE-BODY VIBRATION 

B. Bazrgari,1 A. Shirazi-Adl,1

1

Department of Mechanical Engineering, École Polytechnique, Montreal, Quebec, Canada 

and M. Kasra2 

2

Department of Mechanical Engineering, McMaster University, Hamilton, Ontario, Canada 

Introduction 

Long-term exposure to whole-body vibration (WBV) may increase risk of spine disorders 

[Lings and Leboeuf-Yde 2000], an association that still remains controversial. To elucidate the 

likely causative role of WBV in low-back disorders, however, one needs accurate knowledge on 

muscle forces, spinal loads, and trunk stability. Previous trunk WBV model studies have either 

neglected or oversimplified the trunk redundancy, and trunk stability has not been addressed. 

In continuation of our earlier isometric/transient investigations using a kinematics-driven 

approach [Arjmand and Shirazi-Adl 2006; Bazrgari et al. 2007], this work aims to evaluate 

spinal loads, muscle forces, and stability in a seated subject under a vehicular random vertical 

base excitation with ~ ±1 g peak acceleration contents [Seidel et al. 1997]. The effects of posture 

and coactivity were studied. It is hypothesized that high acceleration contents (shocks) increase 

spinal loads and risk of injury. 

Methods 

A three-dimensional head-pelvis model (Figure 1) made of six non

linear deformable beams to represent lumbar discs and rigid elements to 

represent the rest of the head-thorax segments was used [Bazrgari et al. 2007]. 

­

­

­

Figure 1.—Headpelvis model. 

34
 

The buttocks were modeled by a connector element (compression only) with 

nonlinear properties. Masses, mass moments of inertia, and dampers were 

introduced at different levels based on the literature. A sagittally symmetric 

muscle architecture with 56 muscle fascicles was used. Trunk kinematics, 

distributed gravity, and base excitation were applied onto the model. The non

linear response, muscle forces, and spinal loads were computed using the 

kinematics-driven approach, which satisfies equilibrium at all levels/directions 

while accounting for time-varying muscle forces. Stability analyses were 

performed taking a linear force-stiffness relationship for muscles with a criti

cal stiffness coefficient (q) computed using nonlinear and linear (perturbation 

and eigenvalue) analyses. The input excitation was taken from measurements 

collected at the vehicle seat-driver interface (Figure 2) [Seidel et al. 1997]. 

Two lumbar postures of erect and flexed were considered; in the latter, the 

lordosis was flattened by 10°. The effect of antagonistic activity in abdominal 

muscles and changes in buttocks stiffness on response was also investigated. 

Results 

Base net moments remained positive (flexion) throughout vibration and were larger in the 

flexed posture (Figure 2). Spinal compression/shear forces reached their maximum values at the 

lowermost L5-S1 level in the flexed posture. The critical (minimum) muscle stiffness coefficient 

to maintain stability was substantially influenced by muscle activity, posture, and coactivity in 

the abdominal muscles. The flexed posture improved trunk stability. Introduction of antagonistic 

abdominal activity substantially increased the trunk stability margin in the erect posture by 

diminishing critical q from 89 to 21 at the onset of vibration and from 131 to 39 at the time of 
 

 

 

 

 

peak upward acceleration. Reductions in buttocks stiffness decreased peak accelerations, natural 

frequency, muscle forces, and spinal loads. 

Discussion 

The computed vertical accelerations at the L3 and head (Figure 2) were in good agreement with measurements [Seidel et al. 1997].

 

 

 

 

Figure 2.—Input base 

excitation and acceleration 

(left) with predictions for 

for postures (right). 

 Incorporation of the buttocks with realistic properties diminished the first vertical natural frequency from ~12 to 5.5 Hz, in agreement with the 

literature. The spinal compression/shear forces at the L5-S1 increased significantly because of 

inertial forces—from the respective static values of 535 and 222 N in the erect posture and 717 and 

297 N in the flexed posture to peak values of 1,131 and 508 N in the former and 1,608 and 771 N 

in the latter posture. Based on the premise that excessive loads on the spine could cause injury 

and considering the mild shock contents as compared with values of ±2–6 g reported in off-road 

and industrial vehicles, WBV can be considered as a risk factor. The 10° flattening in the lumbar 

lordosis increased the net moment, muscle forces, and passive spinal loads while substantially 

improving trunk stability. Similarly, the introduction of antagonistic coactivity in the abdominal 

muscles increased extensor muscles activity, spinal loads, and the stability margin. An increase 

in trunk stability occurs at the cost of higher passive loads and hence greater risk of tissue injury, 

suggesting a tradeoff between opposing demands. 

Acknowledgment: Supported by NSERC-Canada and the Aga Khan Foundation. 

References 

Arjmand N, Shirazi-Adl A [2006]. Model and in vivo studies on human trunk load 

partitioning and stability in isometric forward flexions. J Biomech 39(3):510–521. 

Bazrgari B, Shirazi-Adl A, Arjmand N [2007] Analysis of squat and stoop dynamic 

liftings: muscle forces and internal spinal loads. Eur Spine J 16(5):687–699. 

Lings S, Leboeuf-Yde C [2000]. Whole-body vibration and low back pain: a systematic, 

critical review of the epidemiological literature 1992–1999. Int Arch Occup Environ Health 

73(5):290–297. 

Seidel H, Blüthner R, Hinz B, Schust M [1997]. Stresses in the lumbar spine due to 

whole-body vibration containing shocks (final report). Dortmund/Berlin, Germany: 

Schriftenreihe der Bundesanstalt für Arbeitsschutz und Arbeitsmedizin. 

35
 
Session IV: Human Body Modeling and Vibration I 

Chair: Suzanne D. Smith 

Co-Chair: H. P. Wölfel 

Presenter 

A. Mozaffarin 

Wölfel 

Title 

MEMOSIK V: Development and Application of an Active 

Three-Dimensional Dummy for Measuring Vibration 

Comfort on Vehicle Seats 

Page 

37 

B. Bazrgari 

École Polytechnique 

Spinal Loads, Muscle Forces, and Stability under Axial 

Shocks 

39 

H. P. Wölfel 

Darmstadt University of 

Technology 

Application of the Response Spectrum Analysis Method for 

the Evaluation of Human Response to Vibration 

41 

W. J. Pielemeier 

Ford Motor Co. 

Hybrid Modal Analysis of Occupied Seats 43 

M. A. Ksiązek Models of a Human Operator as a Push Force Regulator in 

a Human-Handtool System 

45 

36
 
 

 

MEMOSIK V: DEVELOPMENT AND APPLICATION
 

OF AN ACTIVE THREE-DIMENSIONAL DUMMY
 

FOR MEASURING VIBRATION COMFORT ON VEHICLE SEATS
 

Amin Mozaffarin and Steffen Pankoke
 

Wölfel Beratende Ingenieure GmbH + Co. KG, Höchberg, Germany
 

Introduction 

The unavoidable occurrence of vehicle vibrations affects operating safety, health, and 

comfort in both commercial vehicles and passenger cars. In addition to the vibration exposure at 

the interface between the seat and the occupant, seat transfer functions are usually measured for 

the rating of these effects. Because the transfer functions depend on the dynamic loading of the 

seat, the application and validity of such measurements are only suggestive when using human 

test subjects. However, the use of human subjects is complicated by various restrictions and disadvantages. The development of a vibration dummy is presented here in order to address the 

difficulties in the experimental rating of whole-body vibrations. 

Active Vibration Dummy MEMOSIK V 

The newly developed MEMOSIK V (Figure 1) is an actively controlled, threedimensional vibration dummy that reproduces the vibration behavior of a seated occupant for the 

x-, y-, and z-direction by its dynamic masses.

Figure 1.—MEMOSIK V vibration dummy. 

 It is able to replace the occupant for measurements 

in a vehicle as well as on test rigs. The adoption of the dynamic vibration behavior to the three 

standard mass percentiles (f05 – 5th female; m50 – 50th male; and m95 – 95th male), as well as 

to a particular individual, is easily made through software modifications to the controller setup. 

The appropriate static adoption masses are added or removed. 

The postural variability is accommodated by the complete design range of vehicle seats 

from SUV to roadster. MEMOSIK V comes up with an integrated measurement system and 

enables the repeatable measurement of vibration exposure and seat transfer functions in all three 

spatial directions x, y, and z. 

Active Model Approach 

The active model approach of MEMOSIK V is based on the enhancement of an initially 

passive, ground-excited single degree of freedom (SDOF) oscillator by an actuator and an appropriate control system in order to design a modifiable frequency response (Figure 2). 

37
 
Figure 2.—Equivalent model of the active ground-excited SDOF. 

 

 

 

 

 

The dynamic mass M(s) of this structure results from the contributions of the ground 

mass m 

0

 and the moving mass m, weighted with the amplification function Vm (s). The amplification function Vm (s) represents the relation between the response displacement Q(s) of the moving 

mass and the excitation displacement Q 0(s) of the ground mass (s = iQ is the Laplace variable). 

M(s) = m 

0

 + mVm (s) (1) 

Vm (s) = Q(s) /Q0(s) (2) 

In conjunction with the controller, the actuator enables the modification of the amplification 

function and, thus, the dynamic mass can be adjusted to a given objective function (Figure 3). 

Figure 3.—Amplification functions Vm (s) for x and z, target and measurement. 

Modal Identification 

As a dummy development base, a measuring program was arranged in order to acquire 

the dynamic masses (x, y, and z) of human subjects seated on a rigid test seat. Subsequently, 

the required objective functions were deduced using a modal system identification algorithm to 

parameterize the measurement results for the implementation in the control system. The modal 

identification is based on the approximation of the measured data by the sum of multiple SDOF 

oscillators. Each single oscillator represents a specific mode of the system. 

Bibliography 

Cullmann A [2002]. An active vibration dummy of the seated occupant (in German). 

Düsseldorf, Germany: VDI report No. 492. 

Patent Specification DE 19858517 C1 [1998]. Active vibration model of the human, 

especially of the seated occupant (in German). 

38
 
 

 

 

 

 

 

SPINAL LOADS, MUSCLE FORCES, AND STABILITY UNDER AXIAL SHOCKS
 

B. Bazrgari and A. Shirazi-Adl 

Department of Mechanical Engineering, École Polytechnique, Montreal, Quebec, Canada 

Introduction 

Effective management of back disorders depends in part on accurate estimation of 

spinal loads, muscle forces, and trunk stability in various occupational conditions. Existing biomechanical models of spine have either neglected or oversimplified the nonlinear passive resistance, muscle forces, complex geometry/loading/dynamics of the spine, and equilibrium in all 

spinal levels and directions. Our group has introduced an iterative kinematics-based finiteelement approach to address the existing shortcomings in spinal models. Thus far, the model has 

successfully been applied to simulate a number of isometric and dynamic manual materialhandling tasks [Arjmand and Shirazi-Adl 2005; Bazrgari et al. 2008]. The current work presents 

a novel application of the kinematics-based approach to investigate the seated trunk response 

(e.g., spinal loads, muscle forces, and trunk stability) to vehicular vibration with axial shock 

contents (~4 g) at different frequencies. It is hypothesized that the magnitude and frequency of 

the base excitation, via muscle recruitments (a parameter generally overlooked in earlier 

models), markedly affect the response and risk of injury. 

Methods 

­

The kinematics-driven approach combines experimental and model 

studies to alleviate the kinetic redundancy of the trunk musculoskeletal system. 

Measured trunk kinematics (e.g., rotations at different vertebral levels), along 

with external/gravity loads, were prescribed into a nonlinear, finite-element, 

three-dimensional head-pelvis model (Figure 1) made of nonlinear deformable 

beams to represent lumbar segments and rigid elements for head-thorax seg

ments [Bazrgari et al. 2008].

Figure 1.—Finite-element 

model. 

39
 

 The buttocks were modeled by a connector element (compression only) with nonlinear properties. Masses, mass moments of 

inertia, and dampers were introduced at different levels based on the literature. 

The model was based on data from different sources and close to the 85th 

percentile in the 40–50 years age group. A sagittally symmetric muscle architecture with 56 muscle fascicles was used. Temporal variation of response is 

calculated using the nonlinear iterative kinematics-driven approach. Trunk 

stability was subsequently investigated taking a linear force-stiffness relationship for muscles with a critical stiffness coefficient (q) computed using 

nonlinear and linear (perturbation and eigenvalue) analyses. Axial base 

excitations with ~4 g peaks and frequencies of ~4 and 20 Hz were considered 

based on data at a vertical sinusoidal shaker table [Robinson 1999]. The 

effect of antagonistic activity in abdominal muscles was also investigated. 

Results 

Spinal loads were much greater for the excitation frequency of 4 Hz compared to 20 Hz. 

Maximum net moment at the S1 was also greater in the former (69 versus 37 Nm). Accordingly, 

compression/shear forces at the L5-S1 disc (i.e., the level with maximum loads) for base excitations with 4- and 20-Hz frequencies were, respectively, 3,468/1,236 N and 1,933/697 N. 
 

 

 

Contribution of muscle forces to these loads was significant and generally exceeded that of iner

tial loads (Figure 2).

­

 

 

 

Figure 2.—Input and predictions for 

excitation contents of 4 g-4 Hz (left) and 

4 g-20 Hz (right). 

 The critical (minimum) muscle stiffness coefficient reached values of 350 

and 150 at peak acceleration periods, respectively, under 4- and 20-Hz frequencies, indicating 

risk of instability. In contrast, the system was rather stable in periods with negative acceleration 

or active abdominal muscles. Introduction of antagonistic abdominal coactivity in the case under 

4-Hz frequency substantially increased the trunk stability margin by diminishing critical q from 

88 to 12 at the onset of vibration and from 350 to 63 at the time of peak upward acceleration. 

Amelioration in spinal stability due to antagonistic muscle coactivities was, however, at the 

expense of increases in spinal loads. 

Discussion 

Under various activities such as those involving vehicular vibrations, the spinal loads 

substantially alter depending on the temporal variation of activation in the trunk muscles. The 

relative contributions of gravity, inertial, and muscle forces to the peak compression/shear forces 

at the L5-S1 for the excitation frequency of 4 Hz were, respectively, 10/11%, 39/48%, and 

51/41%, which altered to 9/10%, 35/44%, and 56/46% in the presence of abdominal coactivity 

and to 18/20%, 32/40%, and 50/40% as the excitation frequency increased to 20 Hz (Figure 2). 

Large shock contents (~4 g in the current study) in off-road and military vehicles can significantly increase spinal loads and, hence, risk of injury especially when applied at frequencies in 

the neighborhood of trunk natural frequency (~5 Hz). Such loading conditions also substantially 

deteriorate system stability, thereby demanding compensatory antagonistic muscle coactivity that 

further increases spinal loads and risk of spinal injuries. 

Acknowledgment: Supported by NSERC-Canada and the Aga Khan Foundation. 

References 

Arjmand N, Shirazi-Adl A [2005]. Biomechanics of changes in lumbar posture in static 

lifting. Spine 30(23):2637–2648. 

Bazrgari B, Shirazi-Adl A, Trottier M, Mathieu P [2008]. Computation of trunk equilibrium and stability in free flexion-extension movements at different velocities. J Biomech 41(2): 

412–421. 

Robinson DG [1999]. The dynamic response of the seated to mechanical shock (Dissertation). Burnaby, British Columbia, Canada: Simon Fraser University. 

40
 
APPLICATION OF THE RESPONSE SPECTRUM ANALYSIS METHOD
 

FOR THE EVALUATION OF HUMAN RESPONSE TO VIBRATION
 

H. P. Wölfel1

1

Darmstadt University of Technology, Darmstadt, Germany
 

and J. Hofmann2 

2

Wölfel Beratende Ingenieure GmbH + Co. KG, Höchberg, Germany
 

Introduction 

In view of the large number of workers with back pain, a reliable preventive evaluation of 

vibration exposures on humans at work is of great importance. In addition, the number of inter

national regulations and guidelines dealing with the protection of the worker against vibration 

exposures that have been decreed during previous years make it obvious that we need to under

stand the relationship between occupational exposures and back pain. 

Current evaluations of workplaces with regard to their potential for health impairment 

are based on methods introduced in ISO 2631-1 (1997), which often lead to questionable results 

[Seidel et al., in press]. The main reason originates from the attempt to reduce the vibration 

exposure to a single numerical value (root-mean-square (rms), root-mean-quad, maximum 

transient vibration value, vibration dose value), which facilitates the classification, but at the 

expense of reliability. However, reliability of the classification is critical when dealing with 

health-related matters. 

Methods 

This paper introduces the response spectrum analysis method, which offers a safer and 

more reliable basis for evaluating vibration exposures with regard to their potential for health 

impairment. The response spectrum (RS) should not be confused with a Fourier spectrum, since 

the RS characterizes the response of a vibratory system and not the excitation. To compute the 

RS, a set of single degree of freedom systems (SDOFSs) with different natural frequencies fn is 

excited by the exposure. By taking the maximum value of the response of each SDOFS and 

plotting it over the natural frequency fn, one obtains a curve with the maximum responses, the 

response spectrum (see Figure 1). Since the maximum response of the human directly correlates 

to the potential for health impairment, the response spectrum directly shows whether or not a 

signal can cause health impairment. Since the maximum value is selected and it is not considered 

how often this value appears within the signal, the RS can be used for evaluating the direct risk 

of impairment due to single exposure. A dose consideration is thus not possible. Such a dose 

consideration can be done by picking each local maximum Ai and minimum separated by a zeropass and performing a higher power summation (see Equation 1). Such operation results in the 

response dose spectrum (RDS). The RDS differs from the RS since it considers how often an 

event of certain intensity of human response appears. The RDS Dn for the SDOFS with natural 

frequency fn depends on the power of summation m: a higher power m puts emphasis on single 

events with high amplitude, while a lower power m stresses events with lower amplitude, which 

appear more frequently. 

1 

⎡ ⎤ Dn = ⎢∑( m m 

Ai n ) ⎥ (1) ⎣ i ⎦

­

­

41
 
 

 

 

 

 

EXCITATION: time history 

0 50 100 150 200 250 300 

time 

k f1 df1 

m 

a0(t) 

a(t) f1 

n SDOF systems 

with natural 

frequency f n 

k f2 

m a(t) f2 

df2 

a0(t) 

RESPONSE SPECTRUM 

acceleration 

f

1 f2 

RESPONSE DOSE 

SPECTRUM 

acceleration 

300 0 50 100 150 200 250 -4 

-2 

0 

2 

4 

time 

max(a(t)) 

RESPONSE: time history 

acceleration -2 

0 50 100 150 200 250 -4 

0 

2 

4 

time 

300 

max(a(t)) 

4 

2 

0 

-2 

acceleration -4 

natural frequency fn of SDOF systems 

Figure 1.—Calculation of the response spectrum and the response dose spectrum [Gupta 1990]. 

 

Discussion 

By performing numerous calculations with selected exposure signals, it can be shown 

that the response spectrum analysis method produces much more differentiated results than the 

single value-based methods. The main disadvantage of those methods, which is the disability to 

differ between signals that provide identical rms value (for example) but do have significant 

differences in their spectrum and thus in their response of the exposed human, can be avoided 

using RS and RDS for evaluation. 

With definition of a maximum curve not to be exceeded, this method not only allows for 

evaluation of risk of health impairment, but is also suitable for standardization as well. A similar 

method considering only the RS and not the RDS is standardized in earthquake engineering. 

Several industrial applications for the RS and RDS method are apparent. Due to the ability to consider the response over the whole spectrum at one glance, it is easy to figure out in 

which direction further developments should tend. A seat manufacturer, for example, can decide 

in which frequency ranges the seat behavior must be enhanced to reduce vibration effects on the 

operator. Single-value methods do not provide such information. Such application requires 

definition of standard excitations (typical for the vehicle under investigation) and appropriate 

limit curves. 

References 

Gupta AK [1990]. Response spectrum method in seismic analysis and design of structures. Boston, MA: Blackwell Scientific Publications, Inc. 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

Seidel H, Hinz B, Hofmann J, Menzel G [in press]. Intraspinal forces and health risk 

caused by whole-body vibration: predictions for European drivers and different field conditions. 

Int J Ind Ergon. 

42
 
 

 

 

 

 

 

HYBRID MODAL ANALYSIS OF OCCUPIED SEATS 

William J. Pielemeier
 

Ford Motor Co., Dearborn, MI
 

Introduction and Background 

The measurement of the transmission of vibration through occupied vehicle seats has 

proven useful for understanding the effect of the seat on both vibration comfort and health 

effects [Griffin 1990]. Occupied seat transmissibility provides an input/output relationship 

between the attachment points to the floorpan and the interface between the seat and occupant. 

However, it provides no information on how the mechanical systems in the seat contribute to the 

transmissibility. Modal analysis is a standard tool for analyzing the linear vibration properties of 

mechanical systems. However, traditional modal analysis performed on a seat under the conditions of an occupied seat transmissibility test (i.e., mounted to a shaker system and occupied by a 

human) presents problems. Two new methods are described here that solve those problems and 

produce high-quality results. 

A normal modal analysis excites the system with a wideband force input such as a modal 

hammer, or a shaker and stinger. With multiple inputs, all must be independent and uncorrelated 

for the system to be solved. Output accelerations are measured and transfer functions computed 

from the input forces to output accelerations. These functions are solved for the system modal 

properties, particularly mode frequencies, shapes, masses, and damping. Applying normal modal 

analysis to analyze a seat in the context of an occupied seat transmissibility test presents problems. With the seat attached to a rigid shaker system at four points, it is not mathematically possible for the force inputs to all four attachment points to be independent and uncorrelated. 

Operational modal analysis is an alternate method that is often applied when test conditions do not allow control or measurement of input forces, such analysis of buildings, flying airplanes, etc. It uses only output accelerations, specifying some as references. Cross spectra are 

computed between the references and other outputs, forming a system of equations that can be 

solved for the mode frequencies, shapes, and damping, but not modal masses. 

In practice, operational modal analysis results can suffer from the fact that the spectral 

properties of the excitations are not removed from cross spectra as they are when transfer functions are computed in a normal modal analysis. The presence of the input spectra in the cross 

spectra acts as noise when analyzing for the system properties in the output. When applied to 

modal analysis of a seat transmissibility test, this compromises the results of the analysis due to 

poor signal-to-noise ratio, because many system modes are highly damped and the input spectra 

fluctuations act as lightly damped peaks, which are fitted first by the modal analysis. 

Methods 

A pair of new methods of occupied seat modal analysis take advantage of the fact that the 

seat behaves as an approximately linear system when excitation dynamic range is limited. If an 

occupied seat is excited in pure translation (i.e., one axis at a time), then all of the attachment 

inputs receive the same acceleration. If all of the outputs are divided by a unitless copy of the 

acceleration input, linearity gives the outputs that will be obtained if a perfectly flat unity magnitude white-noise acceleration input was employed. If cross spectra are computed treating the 

input acceleration as an output reference, this process removes the fluctuations of the input 

43
 
 

 

 

 

spectrum and results in a high-quality operational modal analysis. A related idea can be applied 

to normal modal analysis as follows. An acceleration input can be substituted for the force input 

so that the standard transfer function computation removes the input spectral fluctuations and the 

normal modal equations can still be solved, but lack modal masses as with operational modal 

analysis. With the single-axis input condition described above, this acceleration input can be 

treated as a single input (even though at four points), so that dependent equations are not 

obtained. This is called hybrid modal analysis because it is a hybrid of normal and operational 

methods. 

Results 

Figure 1 shows the green line fit of five modes to the red vertical output at the seat 

cushion using a standard operational modal analysis.

 

 

 

4 . 1 3 e - 6 

5 4 . 0 e - 6 Log 

g2 

S y n t h e s iz e d C r o s s p o w e r S E A T : 4 1 : + Z / S E A T : 0 : + Z 

0 . 5 0 H z 3 2 . 3 3 

- 1 8 0 . 0 0 

1 8 0 . 0 0 ° 

S y n t h e s iz e d C r o s s p o w e r S E A T : 4 1 : + Z / S E A T : 0 : + Z 

0 

180 

-180 

10 

mg2 

log 

Hz 32 

Figure 1.—Vertical cushion output (red) amplitude

(above) and phase (below) fitted with five modes of 

an operational modal analysis (green). 

 The vertical axis is in mg2

 for the cross 

spectrum between the vertical output and the wideband input used as a reference for operational 

modal analysis. Note the many sharp peaks due to the superposition of the excitation spectrum 

on the system modes, which the analysis fits with multiple lightly damped modes. Figure 2 is the 

same seat and excitation, analyzed with the second method described above, a normal modal 

analysis with a single vertical acceleration input.

 

 

 

 

 

 

 

0 . 1 2 

2 . 3 1 Log / 

1 .0 0 

S y n th e s iz e d F R F S E A T : 4 1 : + Z /S E A T : 0 :+ Z 

0 . 5 0 H z 3 2 .0 0 

- 1 8 0 . 0 0 

1 8 0 . 0 0 ° 

S y n th e s iz e d F R F S E A T : 4 1 : + Z /S E A T : 0 :+ Z 

0 Hz 32 

amp 

log 

/ 

1.0 

-180 

180 

 Figure 2.—Same vertical cushion and excita

tion as in Figure 1, but treated with hybrid modal
 

analysis.
 

 The vertical axis is the unitless transfer function 

amplitude ratio. Five modes are again used to fit the acceleration/acceleration transfer function 

obtained. Note the removal of the excitation artifacts and the superior fit of the magnitude and 

phase, with the analysis now fitting the more highly damped system modes. Fifty-four output 

points distributed over the entire seat along all three axes, including transmissibility outputs at 

the cushion and back of the seat system, gave similar improvements. 

54 2.3 

­

Discussion 

Animation of the mode shapes from the modal analysis identifies the mechanical sources 

of the resonances in the transmissibility functions. The results above clearly indicate that these 

alternatives to traditional methods of modal analysis provide an excellent fit to experimental data 

and the desired link to the mechanical behavior of the system. 

Reference 

Griffin MJ [1990]. Handbook of human vibration. London: Academic Press, pp. 387–413. 

44
 
 

 

 

MODELS OF A HUMAN OPERATOR AS A PUSH FORCE REGULATOR
 

IN A HUMAN-HANDTOOL SYSTEM
 

Marek A. Ksiązek, Daniel Ziemiański, Zygmunt Basista, Janusz Tarnowski
 

Krakow University of Technology, Krakow, Poland
 

Introduction 

The objective of our work was the synthesis of a model of human operator eye-hand 

reactions for assumed a priori working conditions with handtools. The data obtained from 

experimental investigations of a human operator’s reactions were analyzed and modeled. The 

experiments were conducted on a stand specially designed for 14 volunteers. The registered output signals were approximated by functions that allowed the estimation of their corresponding 

transfer functions. 

Experimental Investigations 

During the experiment, a standing human operator applied measured and registered push 

force on a horizontal handle. The force was the result of screen observation where reference step 

and real push forces were shown side by side. 

The signal of the step input force with a value of 100 N appeared unexpectedly on the 

screen. It was tracked by the operator, whose task was to realize, in the same period of time, 

a similar pressure force on the handle. The system measuring the force realized by the operator 

consisted of strain gauge force sensors. The output analog signal was proportional to the measured value of force. The exemplary time history of input and output signals, chosen from the set 

of analyzed signals, with marked characteristic points and parameters, is shown in Figure 1. 

45
 

 Figure1.—Exemplary time history of step reference and forces realized by human operator. 
 

 

 

 

 

The following parameters were assessed and calculated for each output signal: time delay 

of operator’s reaction, rise time, peak amplitude, overshoot, steady-state error, and settling time. 

Method of Modeling of Human Reactions 

A diagram of the control system modeling human reactions is shown in Figure 2. 

 

u(t) f(t) 

e(t) 

error 

y(t) + 

- -

K(s) 

Figure 2.—Diagram of the investigated system. 

The 

synthesis of the transfer function K(s) of the system was done by minimization of the integral 

quadratic performance index of error e(t) with an assumption of its physical realizability. The 

error e(t) denotes the difference between the real, registered, and approximated output signals. 

Discussion of Results 

An inspection analysis of the registered output signals shows that, in reality, each output 

signal should be modeled by a different transfer function. Among the analyzed signals, some 

different types can be specified. In the present approach, different Laplace transformations were 

applied to process different signals resulting from different types of human reactions. Such 

models allow more precise formulation of human reactions and criteria with regard to many 

aspects of work comfort with handtools. Mathematical modeling of the tool and human operator 

is indispensable for analyzing the dynamic and ergonomic aspects of the handtool-operator system as a whole. It has been shown that such modeling allows for better formulation of work 

comfort criteria and final estimation of design criteria of “human-friendly” handtools. First, the 

problems of reducing harmful vibration and vibration isolation must be addressed. Future experimental measurements will allow for the construction of a human operator model suitable for 

dynamic analysis of a human-machine system. 

Bibliography 

Alexík M [2000]. Modelling and identification of eye-hand dynamics. Simulat Pract 

Theory 8(1–2):25–38. 

Basista Z [2006]. Simulation investigation of an active vibration protection system of an 

operator of a hand-held percussive tool. Eng Trans (Polish Acad Sci) 54(3):173–187. 

Basista Z, Ksiązek M [2004]. Estimation of comfort parameters of an active vibration 

isolation system of handle of percussive power tool. In: Proceedings of INTER-NOISE 2004 

(Prague, Czech Republic, August 22–25, 2004). 

de Vlugt E, Schouten AC, van der Helm FCT [2002]. Adaptation of reflexive feedback 

during arm posture to different environments. Biol Cybern 87(1):10–26. 

McRuer D [1980]. Human dynamics in man-machine systems. Automatica 16(3):237–253. 

This paper is supported by Polish Scientific Committee: PB 1255/T02/2007/32. 

46
 
Session V: Whole-Body Vibration II 

Chair: Bernard Martin 

Co-Chair: Neil Mansfield 

Presenter 

N. Shibata 

Japan National Institute of 

Occupational Safety and 

Health 

Title 

ISO 2631-1 Based Ride Comfort Evaluation of a 

Wheelchair Secured on Day Care Vehicles 

Page 

48 

A. Øvrum 

University Hospital of North

Norway 

Whole-Body Exposure from Heavy Loading Vehicles 

with Different Risk Assessment Outcomes Using 

Recommendations in the ISO-2631 and ISO-8041 

Standards 

50 

L. F. Silva * 

* Author unable to attend conference. 

47
 

Federal University of Itajubá 

Study on Combined Exposure to Noise and WholeBody Vibration and Its Effects on Workers’ Hearing 52 

N. Mansfield 

Loughborough University 

The Compensatory Control Model as a Framework for 

Understanding Whole-Body Vibration 

54 
 

 

 

 

 

 

 

 

 

 

ISO 2631-1 BASED RIDE COMFORT EVALUATION OF A WHEELCHAIR
 

SECURED ON DAY CARE VEHICLES
 

N. Shibata and S. Maeda
 

Japan National Institute of Occupational Safety and Health, Kawasaki, Japan
 

Introduction 

Wheelchairs are an indispensable means of transport for those who have difficulty in 

walking and driving without the aid of mechanical equipment. Nowadays, a great number of 

people receive day care services, which include transport of older and/or disabled people by car 

while seated in wheelchairs secured on the vehicles. Recently, wheelchair users have complained 

of ride discomfort during transport by day care vehicles, which includes a fear of losing balance, 

swaying, falling forward, etc. Vibration transmitted through some surfaces in contact with the 

human body (e.g., seat back, seat surface, floor, and footrest) may cause such complaints. In this 

study, 12-axes vibration measurements based on ISO 2631-1 (1997) were performed to examine 

the effects of vibration on ride comfort for two types of day care vehicles. 

Methods 

­

The experiments were performed with one 

healthy female subject (aged 29 years). The subject 

had no prior experience of exposure to high levels 

or long periods of whole-body vibration occupa

tionally or during leisure time activities. The subject 

was asked to sit in the wheelchair attached to the 

vehicle floor while driving these vehicles. The 

subject used a seat belt to secure her body in the 

wheelchair seat. 

Figure 1 shows a 12-axes vibratory 

acceleration measurement system set up on the 

manual wheelchair used in this study. Figure 1.—Setup of the 12-axes vibratory 

acceleration measurement system. 

48
 

Two triaxial 

seat transducers were secured to the wheelchair: 

one on the seat back, the other on the supporting 

feet surface. Also, a six degree of freedom seat pad accelerometer was secured on the seat surface of the wheelchair. For each transducer, measurement directions were carefully adjusted to 

the basicentric axes of the human body in seated position specified in ISO 2631-1. Measurements of acceleration were obtained for vibration along the 12 axes with a sampling frequency of 

1024 Hz. 

Two types of vehicles, a large (vehicle 1) and a small one (vehicle 2), typically used in 

day care services in Japan, which can carry one wheelchair with the user seated in the 

wheelchair, were evaluated in this study. These day care vehicles were driven on two types of 

roads: alleys and trunk roads (highways). 

Results and Discussion 

As shown in Figure 2, vehicle 1 showed much higher total vibration values on alleys than 

trunk roads. By contrast, vehicle 2 did not show a significant difference in total vibration values 

between alleys and trunk roads. Also, total vibration values observed in vehicle 1 were higher 

than those observed in vehicle 2 for both trunk roads and alleys. This can be explained mainly by 
 

a difference in the mechanical structure of these two vehicles: vehicle 1 had a higher center of 

gravity position than vehicle 2. This structural characteristic caused vehicle 1 to vibrate more 

roughly and have larger displacements than vehicle 2, thereby adversely affecting the comfort of 

those riding in this vehicle. 

 

0 

0.2 

0.4 

0.6 

0.8 

1 

12-axix total value r.m.s. m/s 2 

trunk road 

alley 

Vehicle 1 Vehicle 2 

Figure 2.—Total vibration values obtained for two types of day care vehicles. 

Regardless of vehicle type and road type, the frequency-weighted acceleration value in 

the x direction at seat back was the largest among the 12 acceleration components. In rotation 

effects, the acceleration value in pitching was the highest among the three rotation components. 

These acceleration components are likely to be high when the gradient of the road changes, 

as well as when vehicles start and stop. Reports have indicated that a number of wheelchair users 

felt extremely uncomfortable and sometimes in danger of falling forward. Indeed, some wheelchair users have fallen forward while riding in day care vehicles and have sustained minor injuries. In this regard, our results support the facts. 

 

 

Seat X 

Seat Y 

Seat Z 

Roll 

Pitch

Yaw 

Back X 

Back Y 

Back Z 

Foot X 

Foot Y 

Foot Z 

Seat X 

Seat Y 

Seat Z 

Roll 

Pitch

Yaw 

Back X 

Back Y 

Back Z 

Foot X 

Foot Y 

Foot Z 

0.0 

0.4 

0.8 

1.2 

1.6 

2.0 

Weighted r.m.s. acceleration m/s2

Alley Trunkroad 

0.0 

0.4 

0.8 

1.2 

1.6 

2.0 

Weighted r.m.s. acceleration m/s2 

Alley Trunkroad 

Vehicle 1 Vehicle 2 

Figure 3.—Frequency-weighted rms acceleration for each axis. 

Reference 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

49
 
 

WHOLE-BODY EXPOSURE FROM HEAVY LOADING VEHICLES
 

WITH DIFFERENT RISK ASSESSMENT OUTCOMES USING
 

RECOMMENDATIONS IN THE ISO-2631 AND ISO-8041 STANDARDS
 

A. Øvrum,1 M. Skandfer,1

1

Department of Occupational and Environmental Medicine, University Hospital of North Norway, 


Tromsø, Norway
 

A. Nikanov,2 L. Talykova,2 S. Syurin,2 T. Khokhlov,2

2

Kola Research Laboratory for Occupational Health, Kirovsk, Russia


A. Vaktskjold3 

3

Nordic School of Public Health, Gothenburg, Sweden
 

Introduction 

Whole-body vibration (WBV) is a phenomenon to which vehicle drivers in the mining 

industry are exposed on a daily basis. The purpose of this project was to assess WBV exposure in 

a nonsimulated setting, applying portable equipment during real work cycles in underground and 

open mines on the Kola Peninsula. We calculated different possible risk assessments applying 

the ISO standard 2631-1 for load-haul-dump (LHD) vehicles. The results represent part of a 

cooperative project between the Department of Occupational and Environmental Medicine at the 

University Hospital of North Norway and the Kola Research Laboratory for Occupational Health 

in Kirovsk, Russia. 

Methods 

WBV exposure was measured in the OAO Apatity underground mine on the two most 

commonly used types of LHDs: TORO 007D, TORO 400E, one large transport truck; TORO 

40D and K14 transport locomotives, operating in cycles performing loading, driving, dumping, 

and returning. The ground qualities ranged from soft to rocky surface. A total of 13 measurements were made. Measurement periods ranged from 10 to 52 min, with one to three cycles per 

period. The measurement, processing, analysis, and exposure assessment methods followed the 

guidelines of ISO 2631-1 (1997) and ISO 8041 (2005). 

Results 

50
 

Results from the measurements are shown in Table 1.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1.—Results from the WBV exposure measurements on the TORO 007D, TORO 400E,
 

TORO 40D, and K14
 

LHD 

vehicle Minutes Cycles A(8)x rms 

A(8)x 

VDV 

A(8)y 

rms 

A(8)y 

VDV 

A(8)z 

rms 

A(8)z 

VDV 

Vector sum 

A(8) rms 

TORO 007D 10 3 0.56 4.12 0.44 3.43 0.76 7.80 1.23 

TORO 007D 24 3 0.72 6.68 0.57 6.12 0.73 7.98 1.45 

TORO 007D 17 3 0.81 6.68 0.47 3.95 0.98 10.27 1.61 

TORO 400E 11 3 0.88 6.92 0.51 4.68 1 11.85 1.71 

TORO 400E 11 3 0.72 5.45 0.47 3.63 0.52 4.36 1.30 

TORO 400E 16 3 0.90 7.98 0.64 5.30 0.72 9.95 1.67 

TORO 400E 24 3 0.82 7.81 0.65 6.08 0.83 9.64 1.65 

TORO 40D 36 1 0.53 5.61 0.53 5.76 1.12 18.72 1.52 

TORO 40D 34 1 0.72 7.45 0.57 5.69 1.05 14.93 1.64 

TORO 40D 27 1 0.45 4.79 0.49 5.10 0.89 11.61 1.26 

K14 32 1 0.20 3.01 0.12 1.83 0.19 4.20 0.37 

K14 27 1 0.26 3.87 0.14 1.64 0.31 4.53 0.51 

K14 52 1 0.2 4.05 0.1 2.39 0.29 12.8 0.42 

To calculate A(8) (time-weighted 

acceleration over 8 hr), a time factor of T = 5 hr was used. The ISO standard 2631-1 allows for 

results with these characteristics to be presented in three ways: A(8) root-mean-square (rms) m/s2

, 

A(8) vibration dose value (VDV) m/s−1.75, and vector sum (x, y, and z) A(8) rms (m/s2). 
 

 

 

 

 

Discussion 

­

­

The number, types of vehicles, cycles, and days measured are considered adequate and 

representative in order to make a qualified risk assessment. The recommended basic risk evalu

ation method in ISO 2631-1 is used to present the results in Table 1 as A(8) rms, with results 

comparable to findings in other studies [Boileau et al. 2006; Shrawan 2004]. The characteristics 

of data for LHDs can also be presented using A(8) rms vector sum if two or more axes are com

parable (ISO 2631-1, NOTE in 7.2.2), as seen in Table 1, or using A(8) VDV (if the crest factor is 

high, occasional shocks, transient vibration) (ISO 2631-1, 6.3, NOTE in 6.2.2) [Griffin 2004]. 

Depending on which method is applied, the LHD values provide different risk evaluations 

related to limit and action values (Table 2).

Table 2.—A(8) rms risk evaluation of TORO 007D, TORO 400E, TORO 40D, and K14 and 

risk evaluation of TORO 007D, TORO 400E using other methods in ISO 2631-1 

 Presented as dominant axis A(8) rms, the LHD 

values are below limit value, but above action value (0.5 m/s2

). Presented as vector sum A(8) 

rms, the LHD values are above limit value (1.15 m/s2). Presented as A(8) VDV, the data are 

above and below the action value. Our WBV data on LHDs have substantial vibration levels in 

the x and z directions. The assessment method should therefore rely on the vector sum rather 

than the dominant axis, reducing the number of risk assessment methods for LHDs to one. 

References 

Boileau P-É, Boutin J, Eger T, Smets M [2006]. Vibration spectral class characterization 

of long haul dump mining vehicles and seat performance evaluation. In: Proceedings of the First 

American Conference on Human Vibration (June 5–7, 2006). Morgantown, WV: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and 

Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 

No. 2006–140, pp. 14–15. 

Griffin MJ [2004]. Minimum health and safety requirements for workers exposed to 

hand-transmitted vibration and whole-body vibration in the European Union: a review. Occup 

Environ Med 61:387–397. 

Shrawan K [2004]. Vibration in operating heavy haul trucks in overburden mining. 

Appl Ergon 35(6):509–520. 

51
 
 

 

 

 

 

STUDY ON COMBINED EXPOSURE TO NOISE AND WHOLE-BODY VIBRATION
 

AND ITS EFFECTS ON WORKERS’ HEARING 

Luiz Felipe Silva1

1

Federal University of Itajubá, Brazil 

and René Mendes2 

2

Federal University of Minas Gerais, Brazil 

Introduction 

The purpose of this study was to quantitatively assess occupational exposure to noise and 

whole-body vibration (WBV), analyze the possibility of an association between these two hazards in causing noise-induced hearing loss (NIHL), and discuss feasible means of prevention. 

Methods 

This cross-sectional study was conducted on a population of 141 bus drivers in 

São Paulo, Brazil. The prevalence of NIHL was established through audiometric examinations of 

all workers. The audiograms were classified according to audiometric criteria formulated by 

Merluzzi et al. [1979]. The entire group of bus drivers was classified and stratified internally in 

subgroups of “exposed” and “controls” according to the cumulative length of working time as a 

bus driver. A questionnaire was designed and applied to retrieve occupational history and other 

relevant information. The methodology for noise exposure evaluation was based on the procedures established in ISO 1999 (1990), as well as in the European Economic Community Directive [EEC 1986]. The methodology for whole-body vibration (WBV) exposure evaluation was 

based on the principles established in ISO 2631 (1985). The vibration meter used did not have 

the ISO 2631 (1997) configuration available at the time. Furthermore, the ISO 2631 (1997) 

application still has many controversial points. As Griffin [1998] pointed out: “International 

Standard 2631 (1997) is unclear in several important areas.” The association between the 

dependent variable and the set of explanatory variables was analyzed through nonconditional 

multivariable logistic regression. 

Results 

52
 

It was found that drivers of front-engine buses were exposed to noise levels of 83.6 ± 

1.9 dB(A) (weekly average), while drivers of rear-engine buses were exposed to noise levels of 

77.0 ± 1.1 dB(A). Also, the average of noise exposure equivalents (Leq) for drivers of frontengine buses was 83.1 ± 1.9 dB(A), whereas the average Leqs for drivers of rear-engine buses 

was 76.2 ± 1.7 dB(A). This difference was statistically significant. The average vibration 

acceleration found in the five different bus types analyzed, weighted according to the number 

and length of use of vehicles, was 0.85 m/s2

. Two factors could explain this high value: the 

pavement quality of the streets and the suspension type (parabolic suspension springs) used by 

the bus analyzed. The NIHL prevalence rates were 46% and 24% for the exposed group and the 

reference group, respectively. It was found that the odds ratio for NIHL prevalence, according to 

the univariable analysis, was 2.68 (1.31–5.48, for a 95% confidence interval) for the exposed 

group compared to the reference group. For the best adjusted model, the multivariable analysis 
 

 

 

 

 

showed that age (44 years and older), reference to diabetes, and level of noise exposure (above 

86.8 dB(A)) were risk factors relevant to the development of NIHL. Exposure to WBV, when 

represented by doses, was not significant for NIHL development. 

Conclusions 

The bus drivers analyzed in this cross-sectional study were exposed to relevant WBV 

levels, higher than the permissible exposure levels established by ISO 2631 (1985). Also, the 

noise exposure levels found at the drivers’ work station in front-engine buses were higher than 

those observed at the drivers’ work station in rear-engine buses. No association between WBV 

exposure and NIHL prevalence was observed in this study. In addition, this study could not find 

any interaction between WBV exposure and noise exposure. However, further studies are 

required because other logistic regression models were analyzed showing that an interaction 

between WBV and NIHL could occur, thus increasing the potential risk of adverse health effects 

to workers. 

References 

EEC (European Economic Community) [1986]. Council Directive 86/188/EEC of 

12 May 1986 on the protection of workers from the risks related to exposure to noise at work. 

Official Journal L 137, May 24, 1986, pp. 28–34. 

Griffin MJ [1998]. A comparison of standardized methods for predicting the hazards of 

whole-body vibration and repeated shocks. J Sound Vibration 215(4):883–914. 

ISO [1990]. Acoustics – Determination of occupational noise exposure and estimation of 

noise-induced hearing impairment. Geneva, Switzerland: International Organization for 

Standardization. ISO 1999:1990. 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

Merluzzi F, Parigi G, Cornacchia L, Terrana T [1979]. Metodologia di esecuzione del 

controllo dell’udito dei lavoratori esposti a rumore (in Italian). Nuovo Arch Ital Otol 7(4):695– 

714. 

53
 
 

 

THE COMPENSATORY CONTROL MODEL AS A FRAMEWORK
 

FOR UNDERSTANDING WHOLE-BODY VIBRATION
 

­

­

­

R. Hancock,1

 N. J. Mansfield,1 and J. Vellani1 

1

Environmental Ergonomics Research Centre, Loughborough University, Loughborough, U.K. 

 V. K. Goel,2

2

Indian Institute of Technology Roorkee, India 

Introduction 

There is currently a lack of detailed models of the cognitive effects of whole-body vibra

tion (WBV) [Conway et al. 2007], although some general mechanisms are understood. Previous 

research has often focused on how performance decrements occur. However, a more valuable 

goal would be to specify why these effects occur and find the importance of the component fac

tors that cause these decrements. 

This paper considers Hockey’s [1997] compensatory control model (CCM) as a frame

work for explaining the effects of WBV on activities. The CCM accounts for the hidden costs 

and stressors resulting from maintaining performance as conditions become more difficult. The 

CCM allows for a possible explanation of why objective measures of performance can remain 

stable while workload increases (Figure 1).

Figure 1.—Compensatory control model (adapted from Hockey [1997]). 

 Below an external load threshold, coping occurs 

unconsciously (loop A), but active coping is required for elevated external loads, such as WBV. 

The CCM states that performance protection may occur as difficulty and environmental 

disturbances increase, but at a cost to the performer (e.g., increased psychological stress and 

fatigue); this is known as active coping. This increased effort is maintained by heightened motivation, but if these costs become too great, the motivational strategy will change to minimize the 

effects of long-term stress. The simple methods used in previous experiments to determine 

performance detriments may not be sufficient to capture these underlying stress effects. A framework that predicts these stressors is needed. This framework also needs to take into account that 

performance can compete with other motivational goals (e.g., vigilance; Dorrian et al. [2007]). 

Case Studies 

Three case studies are used to illustrate this active coping approach. All are experimental 

studies by the research team, using WBV as a stressor and measuring workload using NASATLX (task load index), a standard technique using six multidimensional scales including mental 

54
 
 

 

 

 

 

 

 

 

 

 

 

demand, physical demand, temporal demand, performance, effort, and frustration [Hart and 

Staveland 1988]. In case study 1, Hancock et al. [2008] reported the effects of WBV magnitude 

(triaxial random, 0.35, 0.6, 0.87 ms−2 rss) and posture (working on table/lap) on subjective difficulty of reading and writing in Hindi and English. Subjective workload scores increased with 

vibration magnitude. The greatest workload increases were on the frustration and effort subscales. While physical and temporal demand also increased, there was little increase in perceived 

performance rating. Thus, subjects were aware of increased workload associated with their active 

coping due to WBV load. 

In case study 2, Newell and Mansfield [in press] considered the influence of WBV and 

twisted postures on reaction time and error rate for a choice reaction time task. “With armrest” 

conditions showed little or no differences in objective measures of performance with and without 

WBV (x: 1.4; z: 1.1 ms−2). However subjective workload scores increased, particularly in the 

effort and frustration subscales. Thus, performance was maintained at the cost of higher mental 

workload. Without armrests, performance degraded with WBV; this was associated with 

increased workload. Here, the active coping was insufficient to maintain objective performance. 

In case study 3, the influence of WBV (x: 1.4; z: 1.1 ms−2) and 10° seat inclination on 

joystick performance was considered. It was found that subjective workload increased between 

WBV exposure and no exposure, although reaction time did not increase. This again suggests 

that for performance to be maintained, psychological costs are incurred, supporting the CCM. 

Summary 

Three case studies show that objective measures of performance can remain constant 

while subjective workload increases. This supports the CCM, where performance is protected at 

cost to other systems. In particular, fatigue is shown to be one cost induced by active coping. 

This may reduce the vigilance required to maintain task performance [Dorrian et al. 2007]. 

Acknowledgment: This research was funded by the EU Asia-Link ASIE/2005/111000 

CIRCIS (Collaboration in Research and Development of New Curriculum in Sound and 

Vibration). 

References 

Conway GE, Szalma JL, Hancock PA [2007]. A qualitative meta-analytic examination of 

whole-body vibration effects on human performance. Ergonomics 50(2):228–245. 

Dorrian J, Roach GD, Fletcher A, Dawson D [2007]. Simulated train driving: fatigue, 

self-awareness and cognitive disengagement. Appl Ergon 38(2):155–166. 

Hancock R, Mansfield NJ, Goel VK, Narayanamoorthy R [2008]. Influence of vibration 

on workload whilst reading and writing on trains. In: Proceedings of the Ergonomics Society. 

Hart SG, Staveland LE [1988]. Development of NASA-TLX (task load index): results of 

empirical and theoretical research. In: Hancock PA, Meshkati N, eds. Human mental workload. 

Amsterdam, Netherlands: North Holland B.V., pp. 139–183. 

Hockey GRJ [1997]. Compensatory control in the regulation of human performance 

under stress and high workload: a cognitive-energetical framework. Biol Psychol 45(1–3):73–93. 

Newell GS, Mansfield NJ [in press]. Evaluation of reaction time performance and subjective workload during whole-body vibration exposure while seated in upright and twisted postures 

with and without armrests. Int J Ind Ergon. 

55
 
Session VI: Human Body Modeling and Vibration II
 

Chair: David Wilder 

Co-Chair: Arild Øvrum 

Presenter 

S. K. Patra 

Concordia University 

Title 

Defining Reference Values of Vertical Apparent Mass of 

Seated Body Exposed to Vibration 

Page 

57 

H.- J. Kim 

University of Michigan 

Transmissibility of Upper-Body Segments Affecting 

Reaching Tasks Under Vehicle Vibration Exposure 

59 

A. Pranesh 

Concordia University 

Analysis of Distributed Responses of the Seated Human 

Body Exposed to Vertical Seat Excitations 

61 

R. Blood 

University of Washington 

A Comparison of Whole-Body Vibration Exposures 

Across Three Different Types of Bus Seats 

63 

B. Valero 

University of Illinois at 

Chicago 

Ride Comfort Evaluation Using a Three-Dimensional 

Model of a Human Body Focusing the Lumbar Spine 

Area 

65 

56
 
 

 

 

DEFINING REFERENCE VALUES OF VERTICAL APPARENT MASS
 

OF A SEATED BODY EXPOSED TO VIBRATION
 

S. K. Patra,1

 S. Rakheja,1

1

Concordia Centre for Advanced Vehicle Engineering (CONCAVE), Concordia University, 


Montreal, Quebec, Canada
 

P.-É. Boileau,2 H. Nelisse,2 and J. Boutin2 

2

Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), 


Montreal, Quebec, Canada
 

Introduction 

The ranges of biodynamic response of the human body seated without a back support and 

exposed to vertical whole-body vibration have been standardized in ISO 5982 (2001) in terms of 

driving-point impedance and apparent mass (APMS). The ranges were derived from synthesis of 

data reported in different studies, where the total body mass of the subjects varied from 49 to 

93 kg, with mean body mass of 75 kg. The standard also provides reference values for three body 

masses (55, 75, and 90 kg) derived from a linear model. The defined mean values are often interpreted to correspond to mean body mass of 75 kg (DIN standard 45676), which is questionable. 

Furthermore, the lower and upper limits of the idealized range do not represent the biodynamic 

response of any particular body mass group. Many studies [Wang et al. 2004] have shown that 

APMS response of a seated human is strongly influenced by the body mass, excitation magnitude, and sitting posture. It is evident that reliable reference data for particular body masses and 

sitting postures involving back support have not been defined for development of effective 

anthropodynamic manikins. This study involves with the characterization of the biodynamic 

responses of seated human subjects for particular body masses, sitting postures, and excitation 

magnitudes in order to define the reference values. 

Methods 

Experiments were undertaken to measure the APMS responses of seated human subjects 

of particular body masses under vertical vibration. Subjects with body mass in the vicinity of 55, 

75 and 98 kg were recruited for the experiments. A total of 27 adult male subjects (9 subjects in 

each group) participated in the study. Attempts were made to recruit test subjects with body mass 

close to one of the chosen target masses. The APMS characteristics of seated human subjects 

were investigated using a Whole-Body Vehicular Simulator. Measurements were performed with 

each subject seated on a rigid seat without a back support (NBS) and with an inclined rigid backrest (WBS) with an inclination of 12° with respect to the vertical axis. The postural variations 

caused by two different hand positions (hands in lap (LP) and hands on steering wheel (SW)) 

were considered only for the WBS condition. The simulator was programmed to synthesize 

random vertical vibration with flat acceleration power spectrum in the 0.4–20 Hz frequency 

range with three different magnitudes: 0.5, 1, and 2 m/s2

 root-mean-square (rms) acceleration. 

The total static and dynamic force of the seated human subject together with the seat was measured using the force platform, while a single-axis accelerometer was installed in the middle of 

the base platform of the seat to measure acceleration due to vertical excitation. The measured 

data were appropriately corrected for the rigid seat inertia force, and the APMS characteristics of 

the seated human subject were derived using the 50-Hz bandwidth and the frequency resolution 

of 0.0625 Hz. The coherence between the two signals was also monitored during the experiments, which was observed to be close to unity for all of the measurements. 

57
 
Results and Discussion 

 The APMS responses of each subject attained during the three trials were analyzed to 

derive the mean magnitude and phase responses for each mass group, back support condition, 

and excitation magnitude. The data generally revealed excellent repeatability of measurements, 

with peak intrasubject variability in the order of 10% in the vicinity of the resonant frequency, 

which was attributed to relatively small variations in the body mass. Figure 1 illustrates the mean 

APMS magnitude responses of individual subjects within the 55-kg mass group corresponding to 

NBS-LP posture under 0.5-m/s2

 excitation.

100 

80 

APMS (kg) 

60 

40 

20 

0 

0 2 4 6 8 10 12 14 16 18 20 

F requency ( Hz) 

 Figure 1.—Measured APMS responses of 

 seated human subjects (NBS-LP) excited under 

 0.5-m/s2

 rms acceleration. 

The result showed considerable scatter in the magni

tude responses irrespective of excitation level, back support condition, and hand position. The 

scatter in the magnitude response at lower frequencies can be attributed to slight variations in the 

body mass within each mass group. Such low-frequency variations may be suppressed by 

normalizing the biodynamic response data (Figure 2).

­

2.5 

Normalized APMS

2 

1.5 

1 

0.5 

0 

0 2 4 6 8 10 12 14 16 18 20 

Frequency ( Hz) 

 Figure 2.—Normalized APMS responses of 

 seated human subjects (NBS-LP) excited 

 under 0.5-m/s2

 rms acceleration. 

 The normalization, however, cannot 

eliminate the variabilities around the resonant frequencies, which are attributed to strong body 

mass effects. 

 The results, in general, showed strong effects of back support and excitation magnitude, 

apart from the body mass. Moreover, the effects seem to be strongly coupled. The peak APMS 

magnitude varied only slightly with the change in the excitation magnitude irrespective of the 

body mass group. The variation in the primary frequency was observed to be dependent on the 

back support condition. While the primary resonance frequency decreased with increasing 

excitation magnitude for the NBS-LP posture, irrespective of the body mass group, the effect 

diminished for the back-supported posture with hands on steering wheel (WBS-SW). From the 

results, it was concluded that the reference values of the vertical biodynamic responses need to 

be defined for particular body mass, sitting posture, and excitation condition. This study further 

proposes such reference values. 

 

 

 

References 

 DIN [1992]. Mechanical impedances at the driving point and transfer functions of the 

human body. Deutsches Institut für Normung e.V. (German Institute for Standardization). 

DIN 45676. 

 ISO [2001]. Mechanical vibration and shock: range of idealized values to characterize 

seated-body biodynamic response under vertical vibration. Geneva, Switzerland: International 

Organization for Standardization. ISO 5982:2001. 

 Wang W, Rakheja S, Boileau P-É [2004]. Effects of sitting postures on biodynamic 

response of seated occupants under vertical vibration. Int J Ind Ergon 34(4):289–306. 

58 
TRANSMISSIBILITY OF UPPER-BODY SEGMENTS AFFECTING
 

REACHING TASKS UNDER VEHICLE VIBRATION EXPOSURE
 

Heon-Jeong Kim and Bernard J. Martin
 

Human Motion Simulation Laboratory, Center for Ergonomics, University of Michigan,
 

Ann Arbor, MI
 

Introduction 

Vibration perturbation generated by vehicles or terrains is transmitted to the whole body 

of the seated driver and eventual other operators, thus causing discomfort and interfering with 

driving vehicles or performing other tasks in dynamic environments. More specifically, vehicle 

vibration can affect the speed and accuracy of reaching and manipulating tasks associated with 

vehicle operations. Several studies have investigated the effects of vibration on the seated human 

with the goal of improving comfort, safety, or manual performance. The apparent mass of the 

upper torso in static seated postures was analyzed as a function of vibration conditions [McLeod 

and Griffin 1989; Griffin 1990; Paddan and Griffin 2002]. Reach kinematics and performance 

under whole-body vibration (WBV) were quantified by the end-effector trajectory, movement 

time, and aiming error [Reed et al. 2003]. However, to evaluate and predict the effects of WBV 

on reach performance, vibration transmissibility along the path of body segments must also be 

identified since upper-body movement coordination can affect the control of the hand or endeffector. This study investigated changes in the transfer functions of individual upper-body 

segments as a function of various vibration conditions to evaluate the effects of WBV on 

dynamic reach performance. 

Methods 

A reaching experiment was conducted on the U.S. Army’s Ride Motion Simulator. Three 

vibration frequencies (2, 4, and 6 Hz) and two vibration directions (vertical and fore-and-aft) 

were used as input variables to generate six sinusoidal vibration conditions. Thirteen participants 

performed self-paced reaches to five targets representing the overall right-reach hemisphere for 

in-vehicle operations. Twenty-six retroreflective markers were placed on selected body landmarks to record reach movements of seated operators. An optical motion capture system (Vicon) 

was used to acquire movement data with a sampling frequency of 100 Hz. A frequency analysis 

was used to determine the transfer function of body segments, focusing specifically on the 

motion of the torso, right upper arm, and right lower arm-hand. The motions of these three body 

segments were quantified by measuring the displacements of the right shoulder, elbow, and 

fingertip. Relative displacements of individual upper-body segments were transformed into 

transfer functions of the right shoulder, right elbow, and right fingertip in the frequency range of 

0.2–15 Hz, corresponding to the bandwidth of interest. 

Results and Discussion 

The transfer functions of right upper-body segments vary as a function of vibration frequency, direction, and spatial target location. For both vertical and fore-and-aft WBV, transmissibility along the right arm shows the same characteristics. Transmissibility is amplified from the 

59
 
 

shoulder to the fingertip for the 2-Hz vibration, whereas it is attenuated for the 6-Hz vibration. 

For the 4-Hz vibration, all transfer functions have similar peak values. However, the peak fre

quency of transmissibility (transfer function) for each body segment varies as a function of vibra

tion direction (Figure 1).

­

­

 

 

 

Figure 1.—Average peaks of body segment transfer functions as a function of WBV frequency and direction: 

shoulder (1st column), elbow (2nd column), and fingertip (3rd column); vertical WBV (1st row) and horizontal WBV 

(2nd row). 

 For the vertical vibration, the peak of transmissibility occurs at different 

vibration frequencies for the different body segments. For the fore-aft vibration, all the peaks of 

transmissibility decrease monotonously as WBV frequency increases. Transmissibility of body 

segments may also be affected by target location, which is associated with posture differences 

and movement coordination. Further investigation of transfer functions will be used to develop 

an active biodynamic model to predict human behavior in WBV environments and to design controls or interfaces adapted for in-vehicle operations. 

References 

Griffin MJ [1990]. Handbook of human vibration. London: Academic Press. 

McLeod RW, Griffin MJ [1989]. A review of the effects of translational whole-body 

vibration on continuous manual control performance. J Sound Vibration 133(1):55–115. 

Paddan GS, Griffin MJ [2002]. Effect of seating on exposures to whole-body vibration in 

vehicles. J Sound Vibration 253(1):215–241. 

Reed MP, Chaffin DB, Nebel KJ, Rider KA, Mikol KJ [2003]. A pilot study of the 

effects of vertical ride motion on reach kinematics. Warrendale, PA: Society of Automotive 

Engineers, Inc., technical paper 2003-01-0589. 

60
 
 

 

 

ANALYSIS OF DISTRIBUTED RESPONSES OF THE SEATED HUMAN BODY
 

EXPOSED TO VERTICAL SEAT EXCITATIONS
 

A. Pranesh,1

 S. Rakheja,1

1

Concordia Centre for Advanced Vehicle Engineering (CONCAVE), Concordia University, 


Montreal, Quebec, Canada
 

 and R. DeMont2 

2

Department of Exercise Science, Concordia University, Montreal, Quebec, Canada
 

Introduction 

The seated human body’s responses to whole-body vibration (WBV) are characterized 

mainly on the basis of biodynamic functions such as mechanical impedance, apparent mass 

(APMS), or absorbed power measured at the driving point. Responses have also been measured 

in terms of vibration transmitted from the seat to the head (STHT) and other locations of the 

body. It has been suggested that the vibration power absorbed (Pabs) by the human body is 

associated with the potential for tissue damage and may thus be a better indicator of injury risks 

[Vibration Injury Network 2001]. This response quantity, however, is generally evaluated from 

the signals measured at the driving point and may not be associated with localized responses or 

potential injuries in various substructures of the body. Vibration responses measured noninvasively at different segments of the human body could yield a better understanding of the 

localized segmental motions under WBV. Alternatively, anthropometric biomodels, developed 

with adequate consideration of the anatomical substructures and reliable inertial and joint parameters, could be applied for predicting the segmental motions and interactions among the various 

segments. Analytical methods could further facilitate the derivation of response quantities that 

are at present inaccessible by noninvasive techniques, such as the distributed absorbed power 

responses. In this study, a multibody model of the seated human exposed to vertical excitation 

was developed to derive the whole-body distributed biodynamic responses in terms of the power 

absorption characteristics. 

Methods 

An anthropometric model of the seated human body was constructed using 14 rigid 

bodies coupled through joints and force elements to permit vertical translations and sagittal-plane 

rotations of the individual bodies. The upper-body segments (head, neck, thorax, lumbar, torso, 

abdominal viscera, and sacropelvic element), along with upper and lower limbs, were coupled by 

appropriate translational and rotational viscoelastic joints. Inertial properties and joint coordinates were based on a 50th-percentile adult male sitting in a passenger’s posture with “hands in 

lap.” Stiffness and damping values for the viscoelastic elements were identified through minimization of the errors between the model’s biodynamic responses and experimentally measured 

target values. The target values were based on the laboratory-measured APMS and STHT 

responses of six adult male subjects (body mass: 72–79.6 kg) exposed to random vertical vibration (1 m/s2

 rms; 0.5–15 Hz) [Wang 2006]. A gradient-based constrained error minimization 

technique was adopted in the MSC.ADAMS platform, with the model being simulated under a 

vertical swept harmonic excitation at the seat. It was concluded that STHT serves as a better target data for anthropometric model parameter identification than the APMS. Also, modal properties of the former compared better with those reported in the literature. The model derived on the 

basis of STHT error minimization alone was thus used to analyze segmental vibration responses. 

The total and distributed vibration power absorption responses were computed from the energy 

61
 
 

 

 

 

 

 

dissipation across the dissipative components at selected discrete frequencies. Unlike the global 

power responses generally derived from the driving point responses, the model computes the distributed power responses from the relative velocities of different body segments occurring at the 

joints, which obviously are not directly measurable. The estimated power responses across the 

individual joints are normalized by the mass/inertia supported by the joint. 

Results 

In Figure 1A, the total Pabs response of the model is compared with the mean measured 

data reported by Wang [2006] for the same six subjects used for target data set generation. The 

model shows acceptably good agreement with the measured Pabs for the entire frequency range, 

except for small deviations in the vicinity of the primary resonance. The results suggest that the 

model can predict the global absorbed power response reasonably well. Figure 1B shows the distributed energy dissipation characteristics of the viscous joints between model segments in vertical translation, normalized with the total mass supported by the corresponding joint. The results 

suggest highest energy dissipation within the visceral tissue, followed by the buttock, lower lumbar, and neck joints. 

 

A 0.2 

B 4.E-04 

Model C1 

Pabs PSD ((N-m/s)/ Hz) 0.15 

0.1 

0.05 

Measured 

Normalised Pabs (Nm/s)/ kg 

C7 3.E-04 T12 

L5 

Buttock 2.E-04 Viscera 

1.E-04 

0.E+00 0 

0 5 10 15 

Frequency (Hz) 

0 5 10 15 

Frequency (Hz) 

Figure 1.—A, spectral density of total absorbed power; B, model: distributed energy dissipation. 

Discussion 

The anthropometric model developed in this study is capable of effectively predicting 

body segment responses to vertical WBV. The derivation of distributed responses, especially in 

absorbed power, is also definitely possible with this approach. These response variables may 

yield significant insights into potential injury mechanisms in the seated human body due to 

vibration exposure. However, further efforts are needed to achieve improved confidence in the 

model’s predictions. 

References 

Vibration Injury Network [2001]. Review of methods for evaluating human exposure to 

whole-body vibration. Appendix W4A to final report. [http://www.humanvibration.com/EU/ 

VINET/pdf_files/Appendix_W4A.pdf]. Date accessed: May 2008. 

Wang W [2006]. A study of force-motion and vibration transmission properties of seated 

body under vertical vibration and effects of sitting posture [Dissertation]. Montreal, Quebec, 

Canada: Concordia University. 

62
 
 

 

 

 

 

 

 

A COMPARISON OF WHOLE-BODY VIBRATION EXPOSURES
 

ACROSS THREE DIFFERENT TYPES OF BUS SEATS
 

Ryan Blood, Jim Ploger, and Peter W. Johnson
 

University of Washington, Department of Environmental and Occupational Health Sciences,
 

Seattle, WA
 

Introduction 

Low back pain among public transit drivers is quite prevalent. U.S. Bureau of Labor 

Statistics data indicate a high occurrence of low back illness and injury in the transportation 

industry. The relationship between whole-body vibration (WBV) exposure and low back pain 

has been established in prior research [Troup 1998]. Using a low-floor coach bus and a 

standardized test route, the goal of this project was to compare and determine whether there were 

differences across three seat types in their ability to attenuate WBV exposures as defined in ISO 

2631-1 (1997) and ISO 2631-5 (2004). By using a standardized and controlled test route, which 

accurately simulates on-the-job conditions, it is hoped that the analysis of these data may help 

direct and reduce WBV exposures and the potential for subsequent injuries and illnesses among 

bus operators. 

Methods 

Sixteen subjects were recruited for this study. After data collection (dropouts and equipment failure), complete repeated measures data were collected and analyzed from 10 subjects. 

Three different seats were used: (1) a Recaro Ergo M, (2) a USSC Q91 with a standard foam 

seat pad, and (3) the identical USSC Q91 retrofitted with a silicone foam seat pad. Subjects 

drove the bus for approximately 1 hr over a 65-km standardized test route. Seat order was not 

randomized. Vibration was measured using two triaxial accelerometers, one mounted on the seat 

using an accelerometer rigidly mounted in a runner seat pad and the other placed on the floor 

next to the seat using thin high-bond adhesive. Based on ISO 2631-5, which requires a sampling 

rate of at least 160 samples per second, we collected data at 640 samples per second. The standardized test route included surface streets, freeways, and a small section of road containing eight 

speed humps. This route was chosen to represent different types of driving, including start-andstop driving associated with surface streets, impulsive speed hump excursions, and continuous 

freeway travel. The bus used in the study was a 4-year-old, empty, 12.2-m, low-floor coach bus 

(New Flyer Industries, Inc., Winnipeg, Manitoba, Canada). Since there are no steps to impede 

entrance and exit, most major metropolitan bus companies are transitioning to this type of bus. 

The instrumentation developed for this study included a PDA-based portable WBV data 

acquisition system, which collected raw unweighted WBV data at 640 Hz, and the associated 

software to analyze WBV exposures, per ISO 2631-1 and 2631-5. The preliminary analysis of 

the data was focused on analyzing the Z-axis measurements of Aw, vibration dose value (VDV), 

crest factor, maximum continuous peak, and positive and negative raw peaks. Data are presented 

as mean and standard error with significance accepted for p-values less than 0.05. 

Results 

The global positioning system data indicated that there were no significant differences in 

bus speed across the three conditions. Table 1 shows the preliminary results of the analysis of 

time-weighted average (TWA) and peak data across the three different seat types and between 

63
 
the bus seat and floor. Relative to the vibration measured at the floor, the bus seats primarily 

attenuated the vibration exposures. The degree of attenuation depended on the type of measure; 

average measures of vibration (Aw and VDV) were attenuated to a lesser degree than impulsive 

measures (crest factor, maximum peak, and raw peaks). In addition, with the exception of VDV, 

the vibration measured on the bus floor was dependent on seat type. There were also differences 

across seats in the attenuation of the impulsive vibration measures (crest factor, maximum peak, 

and raw positive peak). In general, the Recaro seat had lower impulsive exposures, but what the 

data do not show (not presented) are the seat results by individual road types. On freeways, relative to floor measurements, all seats amplified the Aw exposures; over the speed humps, all seats 

amplified the VDV exposures. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1.—Mean and standard error Z-axis vibration measures by location and seat type (n = 10) 

Seat Floor 

Recaro 

Ergo M 

USSC 

Q91 

USSC Q91 

with silicone p-value Recaro 

Ergo M 

USSC 

Q91 

USSC Q91 

with silicone p-value 

Aw 

(m/s2) 

0.39 

± 0.01 

0.39 

± 0.02 

0.39 

± 0.01 0.98 0.43 ± 0.01 

0.42 

± 0.01 

0.44 

± 0.01 0.04 

VDV 

(m/s1.75) 

9.03 

± 0.23 

9.28 

± 0.46 

9.32 

± 0.43 0.77 11.83 ± 0.46 

12.05 

± 0.44 

11.11 

± 0.20 0.20 

Crest factor 9.65 

± 0.51 

12.09 

± 0.36 

12.63 

± 0.66 0.001 20.92 ± 1.82 

22.85 

± 1.61 

15.26 

± 0.82 0.01 

TWA peak 

(m/s2

) 

3.61 

± 0.18 

4.60 

± 0.27 

4.78 

± 0.32 0.005 8.99 ± 0.82 

9.45 

± 0.70 

6.69 

± 0.39 0.04 

Raw (+) peak 

(m/s2

) 

5.44 

± 0.27 

8.26 

± 1.03 

7.33 

± 0.53 0.03 44.58 ± 5.41 

53.72 

± 2.32 

32.05 

± 3.94 0.01 

Raw (−) peak 

(m/s2

) 

−6.50 

± 0.33 

−6.91 

± 0.42 

−7.08 

± 0.74 0.77 −47.88 ± 6.00 

−62.87 

± 4.87 

−34.02 

± 4.20 0.01 

Discussion 

The bus seats tested in this study seem to be attenuating vibration exposures, but there are 

some exceptions, such as freeways (Aw) and speed humps (VDV). This indicates that the bus 

seats are not optimized for all road types and perhaps bus seat selection could be improved by 

matching or tuning the bus seat to the predominant road type on the bus route. Of particular 

interest is the amplification of exposures on freeways, which can predominate certain types of 

bus routes. Finally, the vibration measured on the bus floor was dependent on seat type. This 

indicates a complex interaction between the bus seat and vibration measured on the floor. 

References 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

ISO [2004]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 5: Method for evaluation of vibration containing multiple shocks. Geneva, 

Switzerland: International Organization for Standardization. ISO 2631-5:2004. 

Troup JDG [1988]. Clinical effects of shock and vibration on the spine. Clin Biomech 

3(4):232–235. 

Zuo L, Nayfeh SA [2003]. Low order continuous-time filters for approximation of the 

ISO 2631-1 human vibration sensitivity weightings. J Sound Vibration 265(2):459–465. 

64
 
 

 

 

 

 

 

 

 

 

 

RIDE COMFORT EVALUATION USING A THREE-DIMENSIONAL MODEL
 

OF A HUMAN BODY FOCUSING ON THE LUMBAR SPINE AREA
 

Bertrand Valero, Farid Amirouche, and Vincent Aledo
 

Vehicle Technology Laboratory, University of Illinois at Chicago (UIC)
 

Introduction 

It is estimated that about 8 million to 10 million U.S. workers are exposed daily to wholebody vibration (WBV) [Wasserman 1987]. These workers are exposed to WBV through various 

sources, e.g., the operation of trucks, forklifts, buses, heavy equipment, farm vehicles, and helicopters. WBV can limit the ability of the operator to perform his or her tasks, which can lead to 

safety issues. Vibration can enter the human body through different pathways, e.g., via the spine 

while driving a vehicle. In the case of heavy vehicle operators, long-term exposure to WBV has 

been linked to severe low back pain in the lumbar region [Schwarze et al. 1998]. A higher rate of 

lumbar syndrome exists among people who have been subjected to this type of vibration for an 

important period of their life. 

Suspension systems have been introduced between the seat and the chassis of such vehicles to minimize body vibration. In parallel to the research done at the UIC Vehicle Technology 

Laboratory on the design of an active seat suspension [Valero et al. 2007], a three-dimensional 

model of the human body is being developed to evaluate the absorbed power and energy transmitted to the human body. The model aims to assert the performance of seat design using the 

latter measures. 

Methods 

A human body model including 19 segments and 18 joints was created. The inertia properties of each segment were defined using anthropometric data for a 95th-percentile American 

male. The properties of a Hybrid III crash test dummy were initially used for the joint characteristics between the segments to build the model. Then, using experimental results found in the 

literature, the joint characteristics were tuned to obtain a first human body resonance comparable 

to the one observed experimentally when the seat-to-head transmissibility was considered. 

A finite-element model of the lumbar spine developed in our laboratory and validated against 

experimental data [Varadarajan et al. 2002] was used to replace the segment representing the 

lower torso. 

The seat suspension design developed in the Vehicle Technology Laboratory was fixed 

on a shaker table. The acceleration signals of the seat and table were collected during the testing. 

These experimental data were applied to a body representing the seat and connected to the 

human body model through the pelvis. The interaction between the body and the seat was 

modeled through a spring and damper in parallel [Amirouche et al. 1997]. The absorbed power 

and the energy transmitted to the body could then be estimated. 

Results 

Experimental results of the semiactive suspension system show a significant reduction in 

the root-mean-square value of the acceleration of the seat. A reduction of the total absorbed 

power by the operator is expected and will allow us to better assess the performance of the suspension design. 

65
 
Figure 1.—Human body model. 

 

 

 

 

 

 

Seat to head transmissibility 

3.5 3.00E+00 

3 m1971 

xu 2.50E+00 

2.5 

eat 

m1995 2.00E+00 

2

xs

xie 

d/

m1978 1.50E+00 

1.5

eaxh

1.00E+00 

1 

5.00E-01 

0.5 

0 0.00E+00 

0 2 4 6 8 10 12 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 

frequency [Hz] Frequency, Hz freqency

Seat-to-head tran transmisibility eat to head ssmissibility 

Figure 2.—Seat-to-head transmissibility obtained through different models (left) and seat-to-head 

transmissibility given by our model including the lumbar spine (right). 

 

 

References 

Amirouche F, Alexa E, Xu P [1997]. Evaluation of dynamic seat comfort and driver’s 

fatigue. Warrendale, PA: Society of Automotive Engineers, Inc., technical paper 971573. 

Schwarze S, Notbohm G, Dupuis H, Hartung E [1998]. Dose-response relationships 

between whole-body vibration and lumbar disk disease: a field study on 388 drivers of different 

vehicles. J Sound Vibration 215(4):613–628. 

Wasserman D [1987]. Human aspects of occupational vibration. Amsterdam, Netherlands: Elsevier Publishers. 

Valero B, Amirouche FML, Mayton AG, Jobes CC [2007]. Comparison of passive seat 

suspension with different configuration of seat pads and active seat suspension. Warrendale, PA: 

Society of Automotive Engineers, Inc., technical paper 2007-01-0350. 

Varadarajan R, Amirouche FML, Wagner F, Guppy K [2002]. Effect of osteoporosis in a 

disc degenerated lumbar spine. In: Proceedings of the Fourth World Congress of Biomechanics 

(Calgary, Alberta, Canada, August 4–9, 2002). 

66
 
Session VII: Hand-Arm Vibration 

Chair: Ren Dong 

Co-Chair: Richard Stayner 

Presenter 

U. Kaulbars 

BGIA 

Title 

Hand-Arm Vibration Exposure in Aircraft Manufacture: 

Measures of Vibration Attenuation 

Page 

68 

T. McDowell 

National Institute for 

Occupational Safety and 

Health (NIOSH) 

Vibration Transmitted From an Impact Wrench to the 

Human Wrist and Elbow 

70 

J. Kim 

University of Cincinnati 

Development of a Receptance Method-Based Modeling 

Technique for Finite-Element Analysis of Hand-Arm 

Vibration 

72 

A. Turcot * 

* Author unable to attend conference.
 

67
 

Institut national de santé 

publique du Québec 

(National Institute of 

Public Health of Québec) 

Noise and Hand-Arm Vibration: A Dangerous Match 74 

S. A. Adewusi 

Concordia University 

Posture Effect on Vibration Transmissibility of the 

Hand-Arm 

76 

R. Dong 

NIOSH Morgantown 

A New Biodynamic Approach to Assess the 

Effectiveness of Antivibration Gloves 

78 
 

 

 

HAND-ARM VIBRATION EXPOSURE IN AIRCRAFT MANUFACTURE:
 

MEASURES OF VIBRATION ATTENUATION
 

Uwe Kaulbars
 

BG-Institute for Occupational Safety and Health (BGIA)
 

Sankt Augustin, Germany
 

Introduction 

Despite a high level of automation, a large number of handheld power tools are still being 

used during the manufacture of aircraft. In particular, high exposure to vibration occurs during 

use of a riveting hammer and dolly. Other tools typically used that give rise to vibration exposure 

are power screwdrivers, saws, and grinding machines. Under the EU Vibration Directive, 

employers are obliged to take state-of-the-art measures to reduce vibration exposure when the 

daily vibration exposure A(8) exceeds 2.5 m/s2

. 

From the range of measures within a vibration attenuation program (as described in the 

CR 1030 series of CEN reports), this work studied the use of alternative working methods and 

the selection of suitable working equipment that could lower vibration exposure. 

Methods 

Measurements were performed under typical work and plant conditions. Each measurement was repeated several times with a number of different test persons experienced in the use of 

the equipment. For riveters, a working cycle of 10 riveting operations was specified for each discrete measurement in order to permit comparison between the different tools for a given task. 

Measurement and analysis of the results were conducted in accordance with ISO 5349. 

Results 

The frequency-weighted acceleration (ahw) values are between 5.4 and 11.5 m/s2

 for 

conventional riveting hammers without vibration damping and between 1.75 and 6.8 m/s2 for 

riveting hammers with vibration damping. These values are not conclusive, however, since they 

are determined from the number of riveting operations over the integration period (duration of 

measurement) according to the hardness of the rivet and the individual pace of progress. The 

number of riveting operations that can be performed before the daily vibration exposure A(8) of 

2.5 m/s2

 is exceeded is 530–1,170 per day for a riveting hammer without damping and 1,830– 

3,000 for a riveting hammer with damping. This takes into account any breaks necessitated by 

the work. 

Higher exposures occur on the dolly. Here the daily vibration exposure is exceeded after 

98 riveting operations per day. The vibration exposure can be reduced by increasing the mass of 

the dolly (Table 1). Owing to the confined conditions, the use of dollies with vibration damping 

is frequently not possible (Figure 1). 

Vibration attenuation can be improved considerably by the use of an alternative working 

method. Blind rivet guns employ an impact-free process; a titanium pop rivet is deformed by 

means of a drawing movement. Blind rivet guns can perform 25,160 riveting operations per day 

before the daily vibration exposure A(8) of 2.5 m/s2

 is exceeded. Threaded joints also generate 

lower vibration exposure than riveted joints. 

68
 
Table 1.—Reduction in vibration exposure as a 

function of dolly weight 

Dolly 

No. of riveting operations 

per day before 2 A(8) = 2.5 m/s isreached 

Tungsten, 3.16 kg 

Steel, 1.61 kg 

Steel, 0.839 kg 

538 

293 

109 

Figure 1.—Use of a riveting hammer and dolly in confined conditions. 

Further relevant vibration exposure occurs during the sawing of 2 mm sheet aluminium 

with a pad saw (ahw = 6.9 ± 1.7 m/s2

) and during the use of random orbital sanders (ahw = 5.1 ± 

1.1 m/s2

). 

Summary and Discussion 

The effects of vibration attenuation for riveting equipment were investigated. Damping 

increases the number of riveting operations for riveting hammers roughly by a factor of three. 

Even more effective for prevention purposes is the use of blind rivet guns, which allow up to 

25,160 riveting operations per day before the daily exposure limit is exceeded. This opens alter

native options to reduce vibration exposure. 

References 

EEC (European Economic Community) [2002]. Directive 2002/44/EC of the European 

Parliament and of the Council of 25 June 2002 on the minimum health and safety requirements 

regarding the exposure of workers to the risks arising from physical agents (vibration) (16th 

individual directive within the meaning of article 16(1) of directive 89/391/EEC). Official 

Journal L 177/13 6.7.2002. 

European Committee for Standardization [1995]. Hand-arm vibration: guidelines for 

vibration hazards reduction – Part 1: Engineering methods by design of machinery. 

CEN/CR 1030-1:1995. 

ISO [2001]. Mechanical vibration: measurement and evaluation of human exposure to 

hand-transmitted vibration. Part 1: General requirements. Geneva, Switzerland: International 

Organization for Standardization. ISO 5349-1:2001. 

­

69
 
 

 

 

 

 

VIBRATION TRANSMITTED FROM AN IMPACT WRENCH
 

TO THE HUMAN WRIST AND ELBOW
 

X. Xu, D. E. Welcome, T. W. McDowell, C. Warren, and R. G. Dong 

Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 


Morgantown, WV
 

Introduction 

Extensive use of impact wrenches could expose operators to prolonged, intensive vibration. Such exposure could result in hand-arm vibration syndrome. The effects of vibration exposure in a structure of the hand-arm system are likely to be more closely related to the actual 

vibration power absorption at that specific structure [Dong et al. 2008]. The objective of this 

study was to characterize the vibration transmitted to the wrist of the operators of impact wrenches. 

Methods 

­

Six experienced male operators of impact wrenches participated in the experiment. Each 

of them used 15 impact wrenches on a simulated work station (Figure 1). For each trial, the sub

ject seated 10 nuts onto plate-mounted bolts in a 30-sec period. Five trials were performed for 

each tool. Triaxial accelerations at three locations (tool handle, wrist, and elbow) were measured. 

In an effort to better simulate actual work situations in the field, postures were not controlled, 

and the subject could use a posture judged to be most comfortable. The six subjects generally 

adopted one of three postures wherein the tool handle was oriented vertically, horizontally, or 

at a 45° angle. Figure 1 shows the 45° working posture. 

 Figure1.—Operation of an impact wrench. 

In addition, a vibration transmissibility test was performed on a one-dimensional (1-D) 

vibration system using a broadband random vibration as the excitation (Figure 2).

 

 

Figure 2.—Measurement of the transmissibility 

on a 1-D test system. 

 Operators 

were instructed to keep the same posture and apply the same grip and push forces to the shaker’s 

instrumented handle as they perceived in the tool test. Whereas the instrumented handle provided the measurement of the input vibration, the accelerometers fixed on the subject’s wrist and 

elbow were used to measure the transmitted vibrations. For each subject, six trials were performed lasting 30 sec each. 

70
 
 

 

 

Results and Discussion 

Even though the vibration magnitudes measured at the three locations are statistically 

significantly different across 6 subjects × 15 tools × 5 trials = 450 trials (ISO-weighted tool 

handle acceleration: 6.26 ± 2.08 m/s2; wrist: 7.49 ± 2.54 m/s2; elbow: 4.05 ± 1.32 m/s2), they are 

reliably correlated with each other ( p < 0.001). The correlation between ISO-weighted tool 

acceleration and wrist acceleration is shown in Figure 3.

 

 

 

 

 

0 

4 

Wrist Acceleration (m/s 2

)

20 

y = 1.1814x 

R2 16 = 0.5754 

12 

8 

0 5 10 15 

ISO-Weighted Tool Acceleration (m/s2

) 

Figure 3.—A correlation relationship. 

Figure 4 shows the transmissibility 

measured with the six subjects on the 1-D test system, together with ISO frequency weighting 

(ISOwt), the transmissibility-derived weighting (WTr-Wrist), and the weighting derived from palm 

vibration power absorption (VPAwt) [Dong et al. 2008].

 

 

 

 

10 

Wrist Transmissibility and

W rist Transm issib ility and Weighting Factors 

W eig htin g F actors

1 

Subj1 Subj2 

0.1 Subj3 Subj4 

Subj5 Subj6 

w VPA Wt. Tr_Wrist 

ISO Wt. 

0.01 

1 10 100 1000 

Frequency (Hz) Frequency (Hz) 

Figure 4.—Vibration transmissibility and 

frequency weighting. 

 The vibration transmissibility shows a 

resonant peak at 31.5 Hz. A similar trend is observed in the VPA weighting. However, this 

resonance is not reflected in the ISO weighting. 

The reliable correlation between ISO frequency-weighted tool acceleration and the wrist 

and elbow accelerations suggests that the ISO weighting partially reflects the characteristics of 

the vibrations transmitted to the wrist and elbow. The results, however, also suggest that the 

ISO weighting may underestimate the effect of the resonance of the hand-arm system. It is feasible to develop a wrist vibrometer for continuously measuring the vibration transmitted to the 

wrist. The exposure duration of the vibration can also be accurately quantified with a wrist 

vibrometer. A method based on wrist vibration measurement may be developed to monitor the 

exposure and to assess the risk of the exposure at least in the wrist-arm subsystem. 

References 

Dong JH, Dong RG, Rakheja S, Welcome DE, McDowell TW, Wu JZ [2008]. A method 

for analyzing absorbed power distribution in the hand and arm substructures when operating 

vibrating tools. J Sound Vibration 311:1286–1304. 

ISO [2001]. Mechanical vibration: measurement and evaluation of human exposure to 

hand-transmitted vibration. Part 1: General requirements. Geneva, Switzerland: International 

Organization for Standardization. ISO 5349-1:2001. 

71
 
 

 

 

 

 

 

 

 

 

DEVELOPMENT OF A RECEPTANCE METHOD-BASED MODELING TECHNIQUE
 

FOR FINITE-ELEMENT ANALYSIS OF HAND-ARM VIBRATION 

J. Kim and S. P. Pattnaik
 

Department of Mechanical Engineering, University of Cincinnati, Cincinnati, OH
 

Introduction 

Exposure to excessive work-related vibration causes musculoskeletal disorders (MSDs), 

including abnormal vascular and neurological function. Hand-arm vibration syndrome (HAVS) 

is a major MSD that often occurs in construction workers and miners. HAVS guidelines have 

been developed that rely mainly on population study and empirical tests, which provide only 

limited information. Especially for the hand and fingers, a direct animal test is not a practical 

option. For this reason, a numerical analysis is very useful in the study of HAVS. This abstract 

reports on the development of an analysis procedure and related techniques for the study of hand 

and arm vibration. 

A substructuring approach such as the receptance 

method [Soedel 2004] enables modeling of the hand and arm 

as a part of the whole body, as shown in Figure 1.

Figure 1.—Hard-arm as a body part. 

72
 

 Representing 

appropriate boundary conditions is necessary to implement a 

receptance method-based analysis. In this abstract, we consider 

modeling of a finger with suitable boundary conditions to model 

its dynamic behavior more realistically. Contact analysis of a 

fingertip using the finite-element analysis (FEA) technique is 

reported as a preliminary step of receptance method-based 

hand-arm analysis. 

Methods 

Receptance method: The receptance method allows the dynamics of a subsystem 

modeled independently, then combined with the other system. As the receptance is defined as the 

ratio of dynamic response and the applied force at the boundary, it is necessary to determine 

boundary conditions for a part of the hand-arm system model. We begin with developing a finger 

model with general boundary conditions. 

Finger model: We consider a detailed model of a finger, including segments of bone, 

nail, and subcutaneous tissue. The fingertip considered in Figure 2 is in contact with a linearly 

elastic PVC polymer probe, which is frictionless. Bone, nail, and probe are modeled by linearly 

elastic materials by taking the data from Yamada [1970], and soft tissue is modeled by nonlinearly elastic and viscoelastic materials by taking the data from Wu et al. [2006a,b]. The 

Young’s moduli of the bone, nail, and probe are 17.0 GPa, 170.0 MPa, and 2.8 GPa, respectively, and Poisson’s ratio is 0.30 for all of them. 

A commercial FEA software package (Abaqus version 6.7) was used, and a plane strain 

analysis was conducted. As the fingertip is being pushed with a probe, the other end is held with 

two sets of springs in either direction. The springs can be modeled to consider the effect of the 

rest of the hand and body. Figure 2 shows the finite-element model with various segments in 

different colors and displacement calculated from a contact analysis in response to 2 mm of 

pad displacement. 
 

 

 

 

Results 

The results shown in Figure 2 are the deformation due to 2.0 mm of displacement by 

probe for a spring-based boundary condition model. 

Figure 2.—Left: finger model. Right: contour plot of the displacement. 

Discussion 

To validate the receptance method-based model, two sets of assemblies can be compared. 

For example, in the finger model we may compare: 

• Finger + rest of body represented by the receptance method; 

• Finger + simple hand + rest of body represented by the receptance method. 

Future Directions 

The current study will be extended to develop a fundamental tool to study HAVS. Techniques will be developed for finite-element vibration analysis of hand parts, considering the 

effects of gripping force and constraints coming from the rest of the body. Important response 

parameters will be identified, and the strategy to calculate them will be developed. 

References 

Soedel W [2004]. Vibrations of shells and plates. 3rd ed. New York: Marcel Dekker, Inc. 

Wu JZ, Dong RG, Welcome DE [2006a]. Analysis of the point mechanical impedance of 

fingerpad in vibration. Med Eng Phys 28(8):816–826. 

Wu JZ, Welcome DE, Dong RG [2006b]. Three-dimensional finite element simulations 

of the mechanical response of the fingertip to static and dynamic compressions. Comput Methods 

Biomech Biomed Eng 9(1):55–63. 

Yamada H [1970]. Strength of biological materials. Baltimore, MD: Williams & Wilkins 

Co. 

73
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NOISE AND HAND-ARM VIBRATION: A DANGEROUS MATCH 

Alice Turcot,1

 Richard Larocque,1 Serge-André Girard,1 Valérie Roy,1

1

Institut national de santé publique du Québec (National Institute of Public Health of Quebec),
 

Quebec, Canada
 

 and Samuel Tétrault2 

2

Faculté de médecine (School of Medicine), Laval University, Quebec, Canada
 

Introduction 

Workers exposed to hand-arm vibration generated by vibrating tools are also exposed to 

high noise levels. Databases supply objective elements regarding not only acceleration levels, but 

also noise levels. A chain saw can produce noise levels up to 111 dBA, and jackleg drills can reach 

115–130 dBA [Umeå University 2008; Boileau et al. 1990]. Studies have shown that forestry 

workers suffer from both hearing loss and “white finger” [Pyykkö et al. 1989]. A study in 

Quebec, Canada, showed that 23% of workers’ compensation claimants who had white finger 

were also eligible for compensation based on degree of hearing loss [Turcot et al. 2007]. The 

study also showed that workers exposed to vibrating tools demonstrated a more severe hearing 

loss when they also had white finger. This loss is more pronounced in the high frequencies 

[Pyykkö et al. 1986; Miyakita et al. 1987]. Furthermore, a study demonstrated that hearing loss 

was about twice as common in men and women who reported finger blanching, including those 

who had never been exposed to noise and who had never been exposed to hand-transmitted 

vibration [Palmer et al. 2002]. Quebec has an audiometric exam database conducted for auditory 

health screening of workers in mobile laboratories under standardized conditions. Our objective 

was to verify if the hearing loss in noise-exposed workers who have white finger is more pronounced than that of workers exposed to the same noise levels from a critical examination of all 

audiometric frequencies with recourse to the data of ISO standard 7029, something that studies 

conducted in the 1980s did not allow. This standard allows valid comparisons with the audiometric exam results of workers exposed to noise and other auditory stress levels (ISO 7029). The 

preliminary results of our study are presented here. 

Methods 

From a database of audiometric exams conducted during 1983–1996, 15,751 were retained 

for analysis (n = 8,528 in mining, and 7,225 in forestry). The following variables were retained: 

age; sex; noise exposure at previous exam; noise experience (exposure length); gross result to 

frequencies 0.5, 1, 2, and 4 kHz; and hearing loss associated with noise (gross loss minus normal 

age loss, as stated in ISO 7029, 50th percentile). Cases of workers affected by white finger disease 

(WFD) and who received workers’ compensation during 1983–1998 were retained for analysis 

(n = 96). Parametric regression curbs allow the tracking of a workers’ hearing profile based on 

experience with noise. ANCOVA tests allow the verification of auditory differences in WFDaffected and unaffected mining and forestry workers. A literature review on the subject was done 

in PubMed (1995–2007, French and English articles with the keywords “noise” and “vibration”). 

A total of 33 articles (animal studies, epidemiology) were retained for analysis. 

Results 

Among the mining and forestry workers examined, the data showed that 7% received 

workers’ compensation for occupational hearing loss. We observed that the auditory profiles 

of mining and forestry workers are comparable to workers in other noisy industry sectors. 

74
 
 

 

 

 

 

 

 

 

Secondly, we observed that workers with white finger (n = 96) showed more pronounced hearing 

loss than mining and forestry workers at the threshold of the 50th percentile of ISO standards. 

This hearing loss is significant. Loss was noted at the 0.5-Hz frequency and at other frequencies 

(1, 2, and 4 kHz). Finally, multivariable analysis showed that noise-exposed workers with more 

than 15 years’ seniority have a 1.44 risk of demonstrating significant hearing loss, and workers 

with white finger have an increased risk of 1.37. 

Discussion 

Mining and forestry workers examined during screening tests demonstrated occupational 

hearing loss and were entitled to workers’ compensation. This low proportion of cases will be 

compared with results from other industry sectors. Hand-arm vibration exposure increases the 

risk of hearing loss in workers affected by WFD. These results agree with the literature. However, our study shows degradation at the low frequencies compared with other studies that show 

a more pronounced effect at the 4-kHz frequency. Some authors have speculated that vibration 

may activate the sympathetic nervous system and induce vasospasm in the organ of Corti reflexively. The mechanisms to explain these low-frequency effects are unknown. These results indicate that preventive measures must be put into place for the short term in these industry sectors 

and reinforce the need to reduce exposure to these two aggressors. Vibration definitely seems to 

be a potential aggressor for hearing loss, and medical questionnaires must include research on 

time exposure to noise and hand-arm vibration, as well as white finger cases in industry sectors 

where workers are exposed to vibrating tools. 

References 

Boileau P-É, Boutin J, Milette L [1990]. Exposition au bruit et aux vibrations mains-bras 

liée à l’opération de foreuses à béquille pneumatique et hydraulique (Exposure to noise and 

hand-arm vibration associated with the operation of pneumatic and hydraulic jackleg drills) 

(in French). Montreal, Quebec, Canada: Institut de recherche en santé et en sécurité du travail 

(IRSST). Études et recherches, report R-046. 

Miyakita T, Miura H, Futatsuka M [1987]. Noise-induced hearing loss in relation to 

vibration-induced white finger in chain-saw workers. Scand J Work Environ Health 13(1):32–36. 

Palmer KT, Griffin MJ, Syddall HE, Pannett B, Cooper C, Coggon D [2002]. Raynaud’s 

phenomenon, vibration induced white finger, and difficulties in hearing. Occup Environ Med 

59(9):640–642. 

Pyykkö I, Starck J, Pekkarinen MS [1986]. Further evidence of a relation between noiseinduced permanent threshold shift and vibration-induced digital vasospasms. Am J Otolaryngol 

7(6):391–398. 

Pyykkö I, Koskimies K, Starck J, Pekkarinen J, Färkkilä M, Inaba R [1989]. Risk factors in 

the genesis of sensorineural hearing loss in Finnish forestry workers. Br J Ind Med 46(7):439–446. 

Turcot A, Roy S, Simpson A [2007]. Lésions professionnelles reliées aux vibrations 

main-bras au Québec, 1993 à 2002 – Partie II: Analyse descriptive des dossiers d’indemnisation 

des travailleurs (Occupational injuries related to hand-arm vibration in Quebec, 1993 to 2002 – 

Part II: Descriptive analysis of worker compensation files) (in French). Montreal, Quebec, 

Canada: Institut de recherche en santé et en sécurité du travail (IRSST). Études et recherches, 

report R-492. 

Umeå University [2008]. Occupational and Environmental Medicine, Department of Public Health and Clinical Medicine, Umeå University, Sweden. [http://www.vibration.db.umu.se]. 

Date accessed: April 2008. 

75
 
 

 

 

 

 

 

 

POSTURE EFFECT ON VIBRATION TRANSMISSIBILTY OF THE HAND-ARM 

S. A. Adewusi,1 S. Rakheja,1

1

Concordia Centre for Advanced Vehicle Engineering (CONCAVE), Concordia University, 


Montreal, Quebec, Canada
 

 P. Marcotte,2 and P.-É. Boileau2 

2

Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), 


Montreal, Quebec, Canada
 

Introduction 

Development of an effective model of the human hand-arm exposed to vibration requires 

characterizing the localized responses apart from the driving point biodynamic responses. 

Although the driving point responses have been widely characterized under a wide range of hand 

forces and postural conditions, the motions of different segments have been reported in a few 

studies in terms of vibration transmissibility of the finger, wrist, elbow, upper arm, and shoulder 

[Aatola 1989; Pyykkö et al. 1976; Reynolds and Angevine 1977]. The effect of posture, which is 

known to alter the biodynamic behavior of the hand-arm system, has not been adequately investigated. Moreover, the effect of push force on the transmitted vibration has not been considered. 

Considering the differences in experimental conditions and measurement locations used in the 

reported studies, extreme differences can be observed among reported transmissibility data, 

which are far greater than those in the reported mechanical impedance properties. The reported 

magnitude responses generally do not show conspicuous peaks that may be related to resonances 

of the hand-arm system. In this study, the vibration transmitted to different segments of the handarm system is characterized under different postures and hand forces. 

Methods 

Experiments were conducted with seven male subjects grasping a 40-mm instrumented 

handle while exposed to zh-axis random vibration (ahw = 5.25 m/s2

) in the 2.5–500 Hz frequency 

range with different combinations of grip (Fg) and push (Fp) forces. Each subject grasped the 

handle assuming two different hand-arm postures: 90° elbow angle with wrist in neutral position 

(P1) and 180° elbow angle (P2). The vibration transmitted to four different locations (wrist, 

elbow 1 (forearm side), elbow 2 (upper-arm side), and shoulder) of the hand-arm were measured 

using three-axis accelerometers attached on Velcro strips. The strips were fastened tightly near 

the joints to minimize the contributions due to skin artifact, while correction for skin deformations was not attempted. The transmissibility responses were obtained along the zh- and yh-axes 

at the wrist and shoulder and along the three axes at the elbow relative to the zh-axis handle 

vibration using the H1 method. Coherence of measurements was monitored to ensure reliability 

of the data. The transmissibility data were examined in both linear and logarithmic scales to gain 

a better understanding of the responses in the low- and high-frequency ranges and to identify the 

characteristic frequencies. ANOVA was used to study the effect of various experimental factors. 

Results 

Figure 1 shows the mean zh-axis transmissibility at the selected measurement locations 

corresponding to the two postures considered. The results show that the zh-axis transmissibility 

of the wrist is the largest at frequencies above 30 Hz and that of the shoulder is the lowest corresponding to the P1 posture. The transmissibility generally decreases from the wrist to the shoulder, although the elbow transmissibility peaks are higher near 12.5 Hz. There is attenuation of 

76
 
 

 

 

 

vibration transmitted to the upper arm for the P1 posture; thus, the elbow acts as a vibration 

absorber. This observation agrees with that of Pyykko et al. [1976]. The yh-axis transmissibility 

of the wrist was observed to be the largest above 30 Hz, while that of elbow 2 was largest below 

30 Hz. Unlike the bent-arm posture, the zh-axis transmissibility for the extended arm (P2) posture 

increases from the wrist to the shoulder in the 2.5–25 Hz frequency range, while the peak magnitude at elbow 2 is the highest. Above 25 Hz, the transmissibility magnitudes decrease from the 

wrist to the shoulder, similar to the trend observed for the P1 posture, while the relative decrease 

is small. The yh-axis transmissibility responses at the elbow 1, elbow 2, and shoulder locations 

for the P2 posture were greater than those for the P1 posture in the low-frequency range; the 

peak magnitude at the shoulder is the highest. The results thus suggest greater transmission of 

low-frequency vibration to the upper arm in an extended-arm posture, which may encourage 

rapid fatigue. The hand-arm system in an extended arm posture tends to attenuate the vibration 

above 25 Hz more effectively than the bent-elbow posture, which limits greater vibration to the 

hand and wrist. The resonant frequencies of the hand-arm system were further identified from 

the data for both postures, which were generally comparable with those reported in earlier 

studies. ANOVA results show that posture and measurement direction are significant at all frequencies, while hand forces are significant above 15 Hz. 

 

 

10 1 10 2 0 

0.5 

1 

1.5 

A c c e le r a tio n R a tio

Wrist 

Elbow1 

Elbow2 

Shoulder 

1 2 

10 0 

A c c e le r a tio n R a tio 

10 1 10 2 0 

0.5 

1 

1.5 

A cce le r a tio n R a tio 

10 1 10 2 

10 0 

A cce le r a tio n R a tio 

10 10 

10 1 10 2 -15 

-10 

-5 

0 

P h a se (ra d ia n s) 

1 2 -20 

-10 

0 

P h a s e (ra d ia n s ) 

Frequency (Hz) 10 10 

Frequency (Hz) 

P1 P2 

Figure 1.—Mean zh-axis transmissibility responses (Fg = 30 N, Fp = 50 N, and ahw = 5.25 m/s2). 

References 

Aatola S [1989]. Transmission of vibration to the wrist and comparison of frequency 

response function estimators. J Sound Vibration 131(3):497–507. 

Pyykkö I, Färkkilä M, Toivanen J, Korhonen O, Hyvärinen J [1976]. Transmission of 

vibration in the hand-arm system with special reference to changes in compression force and 

acceleration. Scand J Work Environ Health 2(2):87–95. 

Reynolds DD, Angevine EN [1977]. Hand-arm vibration. Part II: vibration transmission 

characteristics of the hand and arm. J Sound Vibration 51(2):255–265. 

77
 
 

 

 

A NEW BIODYNAMIC APPROACH TO ASSESS THE EFFECTIVENESS
 

OF ANTIVIBRATION GLOVES
 

Ren G. Dong, Daniel E. Welcome, Thomas W. McDowell, Christopher Warren, and John Z. Wu 

Engineering and Control Technology Branch, Health Effects Laboratory Division, 

National Institute for Occupational Safety and Health, Morgantown, WV 

Introduction 

Antivibration gloves have been increasingly used to help reduce hand-transmitted vibration exposure. A critical question is how much the gloves can help. Another important question 

is whether the effectiveness of the gloves can be further improved. The objectives of this study 

were to develop a new biodynamic approach to predict the vibration transmissibility of the glove 

at the palm and fingers of a human hand and to analyze the mechanisms of the gloves. 

Method 

The proposed method is based on the measurement and modeling of the driving-point biodynamic 

response of the hand-arm system. First, the mechani

cal impedances distributed at the fingers and the palm 

of the hand for a bare hand and a gloved hand were 

measured separately using a reported method [Dong 

et al. 2006]. The same postures and hand forces (30-N 

grip and 50-N push) as those specified in ISO 10819 

(1996) and a broadband random vibration were used 

in the measurement. Six subjects participated in the 

experiments using two types of gloves (glove A: air 

bladder; glove B: gel-filled). Next, the experimental 

data measured with the bare hand were used to establish a five-degree-of-freedom mechanical-equivalent 

model of the hand-arm system (the part with nonfilled 

boxes and their connections in Figure 1) using a 

reported method [Dong et al. 2007].

 

 

 

 

 

 

 

 

 

 

 

 

 

 

x1 

y 

c2 k2 

c3 k3 

c4 k4 

c0 k0 

M2 

M1 

Handle 

M4 

M3 

x0 

c1 k1 

M0 

x3 

c5 k5 

M5 

c6 k6 

M8 

M7 

M9 

M6 

M10 

c7 k7 

c8 k8 

x2 

hand-arm system. 

Fingers 

x4 

Palmwristforearm 

Upper 

armshoulder 

Figure 1.—A model of the gloved Then, based on 

the assumption that the biodynamic properties of the 

hand-arm system remain unchanged when wearing a 

glove, we developed a mechanical equivalent model of the gloved hand-arm system (Figure 1) 

using the experimental data measured with the gloved hand. More specifically, the model param

eters for the bare hand-arm system remain unchanged in the determinations of the elements for 

simulating the glove (the part with filled boxes and their connections in Figure 1) in the model. 

Finally, the glove transmissibility at the fingers is determined by taking the ratio (x4/y) of the 

finger skin motion (x4) in the gloved hand model and the handle motion (y). Similarly, the glove 

transmissibility at the palm is calculated by taking the ratio (x3/y) of the palm skin motion (x3) 

and the handle motion (y). 

­

­

Results and Discussion 

Figure 2 shows the predicted glove transmissibility values, together with those measured 

with the palm adapter method reported in our previous studies [Dong et al. 2003, 2004]. The 

basic trends of the measured and predicted transmissibility data at the palm are consistent, and 

78
 
 

 

 

 

 

 

 

 

their values are comparable below 200 Hz for glove A and 300 Hz for glove B. The isolation 

effectiveness of glove A is better than that of glove B. These observations suggest that both the 

proposed and the adapter method are acceptable, at least for glove-screening tests. The results 

also show that the gloves can provide some vibration reduction at the palm at frequencies higher 

than 30 Hz, but are not effective for reducing finger exposure if the vibration frequency of concern is below 250 Hz. Therefore, it is inappropriate to use the transmissibility measured at the 

palm to estimate the overall vibration reduction for the hand-arm system. Whereas the palm 

transmissibility may be used to help assess palm-wrist-arm system vibration exposure, the finger 

transmissibility may be applied to help assess finger vibration exposure. 

 

 

 

 

0 

0.2 

0.4 

0.6 

0.8 

1 

1.2 

Transmissibility

Fingers 

Palm 

Palm adapter 

Glove A 

0 

0.2 

0.4 

0.6 

0.8 

1 

1.2 

Transmissibility

Fingers 

Palm 

Palm adapter 

Glove B 

10 100 1000 10 100 1000 

Frequency (Hz) Frequency (Hz) 

Figure 2.—Vibration transmissibility functions of an air-bladder glove (glove A) and gel-filled glove (glove B) 

predicted using the proposed method and measured with an adapter method [Dong et al. 2003, 2004]. 

In addition to the transmissibility of the gloves, the glove influences on the vibration 

power absorption distributed in the major substructures of the system can also be predicted using 

the model. Whereas it is unavoidable to impose some interference to the glove-hand-arm system 

in the glove test using an adapter method or an on-the-hand method, this new approach does not 

impose any such interference. The proposed model can be further used to identify the major factors that influence glove effectiveness and to help develop better antivibration devices. 

References 

Dong RG, McDowell TW, Welcome DE, Smutz WP, Schopper AW, Warren C, Wu JZ, 

Rakheja S [2003]. On-the-hand measurement methods for assessing effectiveness of antivibration gloves. Int J Ind Ergon 32(4):283–298. 

Dong RG, McDowell TW, Welcome DE, Barkley J, Warren C, Washington B [2004]. 

Effects of hand-tool coupling conditions on the isolation effectiveness of air bladder antivibration gloves. J Low Freq Noise Vibration Active Control 23(4):231–248. 

Dong RG, Welcome DE, McDowell TW, Wu JZ [2006]. Measurement of biodynamic 

response of human hand-arm system. J Sound Vibration 294(4-5):807–827. 

Dong RG, Dong JH, Wu JZ, Rakheja S [2007]. Modeling of biodynamic responses distributed at the fingers and the palm of the human hand-arm system. J Biomech 40(10):2335– 

2340. 

ISO 10819 [1996]: Mechanical vibration and shock – Hand-arm vibration – Method for 

the measurement and evaluation of the vibration transmissibility of gloves at the palm of the 

hand. Geneva, Switzerland: International Organization for Standardization. ISO 10819:1996. 

79
 
Session VIII: Health Effects 

Chair: Paul-Émile Boileau 

Co-Chair: Christopher Jobes 

Presenter 

H. W. Paschold 

Ohio University 

Title 

Survey of Whole-Body Vibration Awareness and 

Knowledge Among Safety and Health Professionals in 

the United States 

Page 

81 

I. J. H. Tiemessen 

University of Amsterdam 

Effectiveness of an Occupational Health Intervention 

Program to Reduce Whole-Body Vibration Exposure 

83 

J. P. Holland 

University of Washington 

The Role of Whole-Body Vibration and Repeated 

Shock in the Development of Neck Pain and Cervical 

Spine Degeneration: Results of a Systematic Literature 

Review 

85 

T. Jetzer Lumbar Spine Pathology from Whole-Body Vibration 

in Truck Drivers 

87 

T. W. McDowell 

National Institute for 

Occupational Safety and 

Health (NIOSH) 

Evaluating Impact Wrench Vibration Using the Method 

in Proposed Revisions to ISO 8662-7 

89 

80
 
 

 

 

 

 

 

SURVEY OF WHOLE-BODY VIBRATION AWARENESS AND KNOWLEDGE 

AMONG SAFETY AND HEALTH PROFESSIONALS IN THE UNITED STATES 

Helmut W. Paschold
 

School of Health Sciences, Ohio University, Athens, OH
 

Introduction 

Reducing occupational whole-body vibration (WBV) exposure in the United States 

depends on the safety and health (S&H) professional community’s ability to anticipate and 

recognize the hazard. In the course of casual conversations with S&H practitioners, it seemed 

that many had not heard of WBV or had little more than a very basic understanding. An informal 

review indicated that most WBV literature has originated outside of the United States. In 

November 2006, the Ohio University Health Sciences librarian conducted an on-line search of 

the ISO WBV standards. It was found that only three copies were listed in North American 

library catalogs—two in the United States and one in Canada; none of the three is available for 

circulation. Currently, the Occupational Safety and Health Administration does not include or 

refer to WBV in its standards. 

Only two previous survey studies of WBV were found. A survey of workers’ selfreporting WBV exposure [Palmer et al. 2000] determined that an estimated 9 million workers in 

Great Britain were exposed to WBV on a weekly basis, with 4% exceeding action levels. A small 

survey (n=88) of WBV proficiency among construction managers and designers in the United 

Kingdom [Edwards and Holt 2007] revealed that S&H professionals (n=6) in the group selfreported moderate WBV knowledge, averaging 2.33 on a scale of 0 (know nothing) to 4 (know 

everything). 

Based on casual conversations with S&H professionals relative to WBV, relatively few 

published articles or seminar presentations in the United States, the scarcity of available standards, and absence of mandatory federal safety regulations, an assumption was made that the topic 

of WBV is not very well known or understood in the United States. To explore this hypothesis, 

an on-line survey questionnaire about WBV knowledge was prepared and distributed to S&H 

professionals throughout the United States. 

Methods 

81
 

An on-line WBV knowledge survey for U.S. S&H professionals was designed and posted 

on the Web site www.SurveyMonkey.com, chosen for its ease of operation and relatively low 

cost of operation. The survey requested responses in three main categories: 

•	 Knowledge of WBV basics, health effects, standards, and monitoring (self-rating from 

1 (none) to 5 (expert) knowledge) 

•	 Employer size and industrial classification (actual number of employees and industry 

classification according to the U.S. Census Bureau 2002 North American Industry 

Classification System (NAICS)) 

•	 Characteristics of the individual professional, including training, education, experience, and certifications (actual years of experience, university degrees, certification 

titles, continuing education events attended, etc.) 
 

 

 

 

With gracious assistance from the American Society of Safety Engineers (ASSE), an 

e-mail with a link to the hosting Web site was distributed to 21,292 nonstudent ASSE members 

throughout the United States on May 14, 2007. 

Results 

A total of 2,764 persons completed the survey for a response rate of 13.0%. Of the 

respondents, 38.6% reported that they “haven’t heard of WBV.” Among the 61.4% who had 

heard of WBV from one or more sources, 82 persons (5%) reported no ability to define or 

explain WBV. Less than 1% of all respondents reported an expert-level ability to define or 

explain WBV, measure and quantify WBV, or knew the ISO, ANSI, BS, or ACGIH standards 

(all combined). Only one respondent reported expert knowledge of the British WBV Standard. 

Discussion 

The relatively large portion (38.6%) of the surveyed ASSE S&H professionals who 

“haven’t heard of WBV” may be a slight underestimate of the percentage of all “unaware” S&H 

professionals in the United States. ASSE members tend to have higher standards of professionalism than nonmembers; some persons with no knowledge may have exited immediately without 

completing the survey upon reading “WBV” due to unfamiliarity; and persons tend to underreport a lack of knowledge. Further analysis of data is being performed to ascertain individual or 

industry-type characteristics most associated with WBV knowledge levels. The determination of 

the relative absence of S&H professionals’ expertise in WBV suggests that anticipation, recognition, evaluation, and control of the hazard are not occurring as effectively as needed in the 

United States. Enhanced efforts by governmental, professional, and educational organizations 

are needed to increase WBV topic knowledge among S&H practitioners. 

References 

Edwards DJ, Holt GD [2007]. Perceptions of workplace vibration hazards among a small 

sample of UK construction professionals. Eng Construction Archit Manage 14(3):261–276. 

Palmer K, Griffin M, Bendall H, Pannett B, Coggon D [2000]. Prevalence and pattern of 

occupational exposure to whole body vibration in Great Britain: findings from a national survey. 

Occup Environ Med 57(4):229–236. 

82
 
 

 

 

 

 

 

 

EFFECTIVENESS OF AN OCCUPATIONAL HEALTH INTERVENTION PROGRAM
 

TO REDUCE WHOLE-BODY VIBRATION EXPOSURE 

Ivo J. H. Tiemessen, Carel T. J. Hulshof, and Monique H. W. Frings-Dresen 

Coronel Institute for Occupational Health, Academic Medical Center, University of Amsterdam, 

Amsterdam, the Netherlands 

Introduction 

It has been estimated that 4%–7% of all drivers in some European countries, the United 

States, and Canada are exposed to potentially harmful whole-body vibration (WBV). Long-term 

occupational exposure to WBV is associated with an increased risk of low back pain and disorders of the lumbar spine [Lötters et al. 2003]. Despite this, literature on successful strategies to 

reduce WBV exposure in the workplace is scarce [Tiemessen et al. 2007b]. Only one study 

[Hulshof et al. 2006] was identified that systematically evaluated an intervention program aimed 

at reducing WBV exposure. Although the decrease in WBV exposure did not reach statistical 

significance (p=0.06), the results of this study were promising. Most of the research in this field 

is focused on technical prevention, although changing behavior toward WBV determining factors 

might be promising as well. 

The goal of this study was to assess whether introducing an occupational health intervention program leads to an additional decrease in WBV exposure in work situations compared 

to exposure in work situations where “care as usual” is performed. 

Methods 

We used the ASE (attitude, social influence, self-efficacy) model [De Vries et al. 1998] 

as a conceptual model for the design of this intervention study. The theoretical outline of the 

intervention program has been described in detail elsewhere [Tiemessen et al. 2007a]. A group 

of 318 drivers and 9 employers were cluster randomized into 3 groups. The high-exposure 

(≥0.5 m/s2

) intervention group (group 1) received an intervention consisting of an individual 

health surveillance, an informational brochure, an informative oral presentation, and a report of 

the results of the performed measurements of the WBV magnitude. The high-exposure “care as 

usual” group (group 2) and the low-exposure (<0.5 m/s2) “care as usual” group (group 3) 

received care as usual, which consisted only of the informational brochure and the report. At T0, 

the intervention program was implemented. The followup time of the study was 7 months (T1). 

The WBV exposure and the process variables knowledge, attitude, intended behavior, and 

behavior were assessed with self-administered questionnaires and by field vibration measurements according to ISO 2631-1. Data were analyzed using SPSS (version 13.0). To describe the 

effects on WBV exposure and on the process variables due to implementation of the intervention 

program, we used a linear mixed model. Adjustments for the cluster randomization to account 

for both the effects on company and individual level were made. The difference in WBV exposure at T0 and T1 was entered as a continuous outcome variable. Because of nonnormality of the 

data, we assigned ranking to this variable and used a nonparametric model. 

Results 

The response of drivers was 75% (n=240) at T0 and 65% (n=206) at T1. The response of 

the employers/supervisors of the companies was 100% (n=9) at T0 and 89% (n=8) at T1. Of the 

240 drivers at T0, 36% (n=86) seemed to exceed the EU action value for daily exposure of 

0.5 m/s2

 during their work activities. 

83
 
 

 

 

 

Baseline characteristics showed no relevant differences at T0 between the groups. Mixed 

model analysis revealed no significant difference in WBV exposure between groups 1 and 2. 

At T1, however, we found a decrease in WBV for 23% of the drivers in group 1 below the 

0.5 m/s2 EU action value. Mixed model analysis also revealed no significant difference in knowledge, attitude, intended behavior, and actual behavior (see Table 1). Compliance in group 1 to the 

agreed changes during the health surveillance was low; only 19 drivers were compliant for more 

than 50%. 

Table 1.—Gain score (T1 scores -T0 scores) for the three defined groups 

and the employers 

Group 1 (n=65) Group 2 (n=61) Group 3 (n=192) 

Driver 

WBV - gain −0.04 ± 0.21 0.00 ± 0.13 0.11 ± 0.14 

Knowledge - gain 0.25 ± 2.75 0.66 ± 1.63 0.43 ± 2.13 

Attitude - gain −0.97 ± 5.85 −0.31 ± 6.18 0.02 ± 5.46 

Intended behavior 2.24 ± 1.69 2.67 ± 2.06 2.43 ± 2.18 

Behavior - gain 0.66 ± 5.26 −0.23 ± 5.07 −1.06 ± 4.94 

Employer/supervisor Intervention 

group 

“Care as usual” 

group 

Knowledge - gain 0.2 ± 1.10 −1.33 ± 3.79 

WBV - policy 1.4 ± 3.51 4.0 ± 4.36 

The implementation failed to increase the knowledge of the employers both in the intervention and the “care as usual” groups, but a tendency for an increase in company policy was 

found (see Table 1). 

Discussion 

Implementation of the presented intervention program was not effective in reducing the 

average WBV exposure on group level significantly. However, for a substantial portion of the 

drivers in the intervention group, the daily vibration exposure was reduced to a level below the 

EU action value. Besides aiming at technical preventive measures, future research should also 

focus on the role of the individual driver in preventing adverse effects of WBV exposure. 

References 

De Vries H, Mudde AN, Dijkstra A, Willemsen MC [1998]. Differential beliefs, perceived social influences, and self-efficacy expectations among smokers in various motivational 

phases. Prev Med 27(5):681–689. 

Hulshof CTJ, Verbeek JHAM, Braam ITJ, Bovenzi M, van Dijk FJH [2006]. Evaluation 

of an occupational health intervention programme on whole-body vibration in forklift truck 

drivers: a controlled trial. Occup Environ Med 63:461–468. 

Lötters F, Burdorf A, Kuiper J, Miedema H [2003]. Model for the work-relatedness of 

low-back pain. Scand J Work Environ Health 29:431–40. 

Tiemessen IJH, Hulshof CTJ, Frings-Dresen MHW [2007a]. The development of an 

intervention programme to reduce whole-body vibration exposure at work induced by a change 

in behaviour: a study protocol. BioMed Cent Public Health, Nov 15;7:329. 

Tiemessen IJH, Hulshof CTJ, Frings-Dresen MHW [2007b]. An overview of strategies to 

reduce whole-body vibration exposure on drivers: a systematic review. Int J Ind Ergon 37(3): 

245–256. 

84
 
 

 

 

 

THE ROLE OF WHOLE-BODY VIBRATION AND REPEATED SHOCK IN THE
 

DEVELOPMENT OF NECK PAIN AND CERVICAL SPINE DEGENERATION:
 

RESULTS OF A SYSTEMATIC LITERATURE REVIEW
 

John P. Holland,1

1

Principal, Holland and Associates, Seattle, WA
 

Clinical Faculty, Department of Environmental and Occupational Health Sciences,
 

University of Washington, Seattle, WA
 

Carole L. Holland,2

2

Principal, Holland and Associates, Seattle, WA 

Affiliate Faculty, Seattle University, Seattle, WA
 

and John Webster3 

3

Consultant, San Diego, CA
 

Retired, Chief of Orthopaedic Surgery, San Diego Naval Medical Center, San Diego, CA
 

Background 

Whole-body vibration (WBV) has been proposed as a risk factor for the development of 

neck pain secondary to degeneration of spinal structures. We conducted a systematic review of 

the scientific literature to evaluate the strength of the evidence for an association between WBV 

and neck pain or cervical spine degeneration. 

Methods 

A comprehensive search was conducted of bibliographic databases through August 2007. 

Two investigators independently reviewed all abstracts to identify relevant articles. Full-text 

versions of potentially relevant articles were systematically evaluated. All articles containing 

original data were graded for quality of study design and precision of exposure and outcome 

classification. Due to heterogeneity in study designs, exposure classification, and outcome classification, meta-analysis was not attempted. 

Adverse health outcomes were stratified into five categories: (1) self-reported symptoms 

of neck pain, (2) symptoms of neck pain and consultation with a health care provider, (3) symptoms of neck pain and evidence of cervical spine degeneration on imaging, (4) injury claim or 

leave of absence for neck pain derived from administrative databases, and (5) symptoms of neck 

pain, evidence of cervical spine degeneration on imaging, and positive electrodiagnostic evidence for radiculopathy. 

Exposure estimates were stratified into four categories: (1) occupational title, (2) selfreported exposure to WBV or history of occupational driving, (3) quantification of time exposed 

to WBV on a specific job, and (4) measurement of WBV according to national or international 

consensus standards. No article was excluded based on classification of disease or exposure estimates. However, greater weight was assigned to articles with objective or quantitative measures 

of exposure and clinical outcome. 

A qualitative synthesis of study results was done using generally accepted guidelines for 

the determination of causality, including (1) strength of the association, (2) consistency of the 

association, (3) specificity of the association, (4) temporality of the association, (5) biological 

85
 
 

plausibility of the association, (6) coherence of the association, (7) experimental evidence for the 

association, and (8) dose-response relationship. 

Results 

The bibliographic search identified 269 relevant citations, and 60 articles were selected 

for systematic review. Most of the epidemiological studies evaluated occupational groups, 

including occupational drivers, heavy equipment operators, aircraft pilots, and industrial 

workers. Generally, classification of adverse health consequences was based on self-reported 

symptoms of neck pain derived from questionnaires. Indices of severity, typically consultation 

with any health care provider for neck pain or lost time from employment, were derived from 

questionnaires. Exposure to WBV was typically classified based on occupational title or selfreported exposure. Quantitative measurements of WBV exposure (i.e., frequency, intensity, 

duration, and temporal patterns of exposure) were typically not reported. 

Conclusions 

Presently, there is insufficient evidence of a causal association between WBV and neck 

pain or cervical spine degeneration. Generally, study designs were inadequate, WBV exposure 

was not quantified, outcome definitions lacked specificity, and potential confounders were not 

rigorously examined. 

86
 
 

 

 

 

 

 

 

LUMBAR SPINE PATHOLOGY FROM WHOLE-BODY VIBRATION
 

IN TRUCK DRIVERS
 

Thomas Jetzer
 

Occupational Medicine Consultants, Minneapolis, MN
 

Introduction 

It has long been postulated that the lumbar spines of drivers of industrial vehicles are 

adversely affected by whole-body vibration (WBV) transmitted through their seats. The literature 

contains many studies that imply that WBV from driving industrial vehicles can cause various 

levels of pathology to the lumbar spine [Andrusaitis et al. 2006; Camerino et al. 1997]. However, 

these studies have had difficulty isolating the effects of WBV from other confounding factors 

that can affect the integrity of the lumbar spine, including the effect of aging, excess weight, 

posture, associated lifting tasks, and genetic-related variability [Seidel 2005; Lings and 

Leboeuf-Yde 1998]. Analysis of the effect of WBV on the lumbar spine can be addressed from a 

number of perspectives, including the mechanical aspects often characterized by spinal modeling 

[Matsumoto and Griffin 2001; Seidel et al. 2001] due to difficulty of such measurement in the in 

vivo environment, cellular damage analysis either from the biochemical perspective or by way of 

various imaging methods, or by epidemiological analysis [Drerup et al. 1999; Hirano et al. 

1988]. While many studies have implied that WBV is a significant cause of lumbar spine 

pathology, this opinion is valid only if it is supported by analysis of data from the work 

environment. 

The purpose of this study was to assess the incidence of low back pathology in drivers 

from various industries. The industries were chosen to show variation in the drivers’ tasks with 

regard to lifting and physical activities. Airline pilots were used as controls to negate the effect 

of posture and seating endurance. The subjects were selected randomly from the clients of an 

occupational clinic, with repeated visits of the same individuals to ensure consistency in medical 

history and physical findings. Data were analyzed to determine if there is any correlation 

between driving, job activities, or physical and medical information to support the implication 

that vibration associated with driving activities can cause lumbar spine pathology. 

Method 

Chart analyses of 1,697 drivers from various industries, including over-the-road truckers, 

trash collector drivers, utility linemen, movers/drivers, and school bus drivers, were compared to 

those of a similar group of airline pilots. The points of comparison included age, body mass 

index (BMI), work history, and medical history. The aforementioned industries were selected 

because of the differences in physical activity required by the jobs along with significant and 

similar amounts of driving activity. A comparison was made between these groups of drivers to 

determine if there was a significant difference in any of the parameters. 

Results 

Analysis of the comparison parameters indicated that the strongest association with lumbar spine pathology was weight, BMI, and job activity. Bus drivers and the control group of 

pilots had similar profiles of lumbar pathology. The level of pathology was most associated with 

nonvibration related to age, work activities, and BMI in all groups. There was very little 

87
 
 

 

 

 

 

pathology that was not explainable by a review of medical histories independent of any driving 

activities. 

Discussion 

The results of this study indicate that lumbar spine pathology can be explained by confounding factors of jobs, work history, age, and BMI characteristics independent of driving 

activities. In other words, BMI, age, and work history can explain the occurrence of spinal 

pathology in drivers as opposed to any vibration to which they may be exposed in the job. While 

there is evidence that individuals with significant spinal preexisting pathology may have poor 

tolerance from WBV due to vibration resonance with abnormal spinal and neurological architecture [Vanharanta et al. 1998; Yrjämä et al. 1996], the evidence does not support that this pathology is caused by vibration in industrial driving addressed in this study. With the advent of new 

seat technologies that are widely deployed throughout the trucking industry, there is little basis to 

state that workers are exposed to enough WBV to result in significant pathology. 

References 

Andrusaitis SF, Oliveira RP, Barros Filho TE [2006]. Study of the prevalence and risk 

factors for low back pain in truck drivers in the state of São Paulo, Brazil. Clinics 61(6):503– 

510. 

Camerino D, Molteni G, Volponi R, Simionato B, Dondè I [1997]. Public transportation 

driving and disorders of their vertebral spine: subjective evaluation of the risks (in Italian). 

Med Lav 88(5):382–395. 

Drerup B, Granitzka M, Assheuer J, Zerlett G [1999]. Assessment of disc injury in subjects exposed to long-term whole-body vibration. Eur Spine J 8(6):458–467. 

Hirano N, Tsuji H, Ohshima H, Kitano S, Itoh T, Sano A [1988]. Analysis of rabbit intervertebral disc physiology based on water metabolism. II. Changes in normal intervertebral discs 

under axial vibratory load. Spine 13(11):1297–1302. 

Lings S, Leboeuf-Yde C [1998]. Whole body vibrations and low back pain (in Danish). 

Ugeskr Laeger 160(29):4298–4301. 

Matsumoto Y, Griffin MJ [2001]. Modelling the dynamic mechanisms associated with 

the principal resonance of the seated human body. Clin Biomech (Bristol, Avon) 16(Suppl 1): 

S31–44. 

Seidel H [2005]. On the relationship between whole-body vibration exposure and spinal 

health risk. Ind Health 43(3):361–377. 

Seidel H, Bluthner R, Hinz B [2001]. Application of finite-element models to predict 

forces acting on the lumbar spine during whole-body vibration. Clin Biomech (Bristol, Avon) 

16(Suppl 1):S57–63. 

Vanharanta H, Ohnmeiss DD, Aprill CN [1998]. Vibration pain provocation can improve 

the specificity of MRI in the diagnosis of symptomatic lumbar disc rupture. Clin J Pain 14(3): 

239–247. 

Yrjämä M, Tervonen O, Vanharanta H [1996]. Ultrasonic imaging of lumbar discs combined with vibration pain provocation compared with discography in the diagnosis of internal 

anular fissures of the lumbar spine. Spine 21(5):571–575. 

88
 
 

 

 

 

 

 

 

 

 

 

EVALUATING IMPACT WRENCH VIBRATION USING THE METHOD
 

IN PROPOSED REVISIONS TO ISO 8662-7
 

T. W. McDowell, R. G. Dong, X. Xu, D. E. Welcome, and C. Warren 

Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 


Morgantown, WV
 

Introduction 

ISO 8662-7, the international standard for evaluating vibration emissions from impact 

wrenches, is undergoing a systematic review and revision. The revisions are designed to more 

closely simulate actual vibration in the workplace, ensure that the end results will fall into the top 

quartile of what is actually experienced by a variety of workers in different work situations, produce a vibration result that could be easily translated into risk assessment analysis, and be able to 

be applied to a cross-section of all threaded fastener tools [ISO 2006]. While the current standard 

calls for single-axis vibration measurements to be made while the tool acts against a braking 

device, the revised procedure specifies that triaxial vibration measurements be made over the 

course of a series of 30-sec trials that involve the seating of 10 nuts onto plate-mounted studs 

or bolts. 

In order to provide information toward the improvement of the impact wrench testing 

method, NIOSH constructed the proposed test rig and conducted impact wrench evaluations 

using the revised procedure. The objectives of this study were to compare methods for quantifying impact wrench vibrations and perform a general evaluation of the proposed revisions to 

ISO 8662-7. 

Methods 

Six male experienced impact wrench operators used 15 impact wrenches in the simulated 

work task. Three samples each of four pneumatic models (A through D) and one batterypowered model (model E) were used. The test rig consisted of two steel plates vertically 

mounted on a concrete block. The plates featured channels and holes to accommodate 10 steel 

bolts arranged in 2 evenly spaced rows. Each bolt was fitted with a nut, two Belleville washers, 

and a matching flat washer. Triaxial vibration measurements were made over the course of a 

series of 30-sec trials that involved the seating of 10 nuts onto the bolts. Each operator completed 

five 10-nut trials with each of the 15 tools for a total of 75 trials in a test session. 

For the four pneumatic tools, vibration was measured at the tool handle and at the front 

portion of the tool housing. For the smaller battery-powered tool, only handle vibration was measured. Vibration data were collected for each one-third octave band with center frequencies from 

6.3 to 1250 Hz. 

Results and Discussion 

As expected, the within-tool acceleration values varied less than the within-operator 

values. ANOVAs for ISO-weighted (ISO 5349-1) and unweighted acceleration each revealed 

that both tool and operator are significant factors, as well as their interaction (p < 0.001). However, as indicated in Table 1, an evaluator rank-ordering the tools by acceleration would draw 

different conclusions depending on whether or not ISO weighting was applied. Thus, it may be 

best to report both acceleration values. 

As shown in Figure 1, there is a strong correlation between ISO-weighted acceleration 

measured at the tool handle and that measured on the motor housing (R2

 = 0.875, p < 0.001). 

This relationship holds true for unweighted acceleration. Thus, for tool-screening purposes, 

it may not be important to measure vibration at multiple tool locations. 

89
 
Table 1.—Vibration measured at the tool handle for each 

 subject and tool type 

2 ISO-weighted acceleration (m/s ) 

Tool ModelB ModelA ModelE ModelD ModelC
 

Operator Mean SD Mean SD Mean SD Mean SD Mean SD
 

3 2.7 0.2 5.5 0.5 7.1 0.3 6.5 0.3 8.0 1.0 

2 2.7 0.1 6.0 0.4 6.6 0.6 6.8 0.6 7.9 0.7 

5 3.2 0.3 6.3 0.3 6.4 0.8 7.7 0.1 8.8 0.8 

1 2.6 0.3 6.4 0.8 6.5 0.5 8.2 1.4 8.9 2.5 

6 3.2 0.5 7.1 0.7 7.3 0.8 7.7 0.7 10.3 1.5 

4 3.0 0.2 7.6 0.5 8.3 0.8 9.9 0.8 9.7 0.7 

Average 2.9 0.3 6.5 0.5 7.0 0.6 7.8 0.6 8.9 1.2 

2 Unweighted acceleration (m/s ) 

Tool ModelB ModelA ModelE ModelD ModelC 

Operator Mean SD Mean SD Mean SD Mean SD Mean SD 

3 27.0 3.3 100.6 9.3 202.4 3.3 173.5 10.0 129.2 6.8 

2 26.4 1.5 114.0 10.4 153.0 16.4 209.6 10.8 134.1 17.6 

5 35.3 1.9 119.0 5.8 147.3 21.1 209.0 5.9 155.5 15.7 

1 30.1 6.4 109.0 20.4 145.6 14.9 219.0 34.4 161.6 37.8 

6 30.8 1.6 138.5 3.2 161.1 15.4 228.7 11.2 210.4 32.3 

4 29.2 1.9 130.5 3.8 191.1 26.6 251.6 20.9 192.2 18.9 

Average 29.8 2.8 118.6 8.8 166.7 16.3 215.2 15.5 163.8 21.5 

 

 

 

 

Housing Weighted Acceleration (m/s2) 16 

12 

8 

4 

0 

y = 1.1228x 

R = 0.875 2 

0 4 8 12 16 

Handle Weighted Acceleration (m/s2) 

Figure 1.—Handle versus housing vibration. 

 

 

 

 

 

 

 

Both the current and proposed impact wrench assessment standards call for testing by 

three tool operators. However, a power analysis [Montgomery 2001] revealed that three tool 

operators may not be enough for reliable tool screening. Based on the acceleration variance 

observed in this study, at least five tool operators would be required to reliably rank-order all 

five tool models using this revised procedure (α = 0.05, β = 0.20, p < 0.05). 

It is generally recognized that work posture and applied hand forces can significantly 

affect hand-transmitted vibration exposure [Griffin 1997]. In light of these observations, it may 

be useful to modify the impact wrench test procedure in an effort to reduce variability in the 

results. For example, to better control work posture, the operator could stand on a platform with 

adjustable height. Thus, elbow and shoulder angles could be more standardized. To help evaluate 

the influence of applied forces, a force plate could be added to the platform to measure ground 

reaction forces. 

While this test setup may not provide reasonable simulations for all work tasks involving 

impact wrenches, the apparatus and test procedure seem to generate appropriate data for tool 

screening for a wide variety of impact wrench models and many common workplace operations. 

References 

Griffin MJ [1997]. Measurement, evaluation, and assessment of occupational exposures 

to hand-transmitted vibration. Occup Environ Med 54(2):73–89. 

ISO [1997]. Hand-held portable power tools – Measurement of vibrations at the handle – 

Part 7: Wrenches, screwdrivers and nut runners with impact, impulse or ratchet action. Geneva, 

Switzerland: International Organization for Standardization. ISO 8662-7:1997. 

ISO [2001]. Mechanical vibration – Measurement and evaluation of human exposure to 

hand-transmitted vibration – Part 1: General requirements. Geneva, Switzerland: International 

Organization for Standardization. ISO 5349-1:2001. 

ISO [2006]. Round robin test setup and procedure for proposed changes to ISO 8662-7. 

ISO/TC 118/SC 3/WG 3 – Vibrations in hand-held tools – Ad hoc group for wrenches. 

Montgomery DC [2001]. Design and analysis of experiments. 5th ed. New York: 

John Wiley & Sons, pp. 107–109. 

90
 
Session IX: Epidemiology and Standards II
 

Chairman: Danny Riley
 

Co-Chair: Sandya Govindaraju
 

Presenter Title Page 

D. Riley 

Medical College of 

Wisconsin 

Effect of an FMRI-Compatible Piezoelectric Vibration 

Actuator on Rat Tail Skin Perfusion 

92 

M. A. Loffredo 

Medical College of 

Wisconsin 

Vibration-induced Nerve Injury and Recovery in a Rat Tail 

Model 

94 

S. Govindaraju 

Medical College of 

Wisconsin 

Effects of Vibration Exposure on Arterioles in Rat Tail 

Nerves 

96 

K. Krajnak 

National Institute for 

Occupational Safety and 

Health (NIOSH) 

Reduced Sensory Nerve Thresholds May Be Indicative Of 

Nerve Injury After Repeated Exposure To Vibration 

98 

A. J. Brammer 

University of Connecticut 

Health Center and 

National Research 

Council (Canada) 

Influence of Change in Work Practices on Vibrotactile 

Perception: Preliminary Analysis of a Prospective Study of 

Forestry Workers 

100 

Y. Ye 

University of 

Southampton 

Individual Variability in Changes in Finger Blood Flow 

Induced by Hand-Transmitted Vibration 

102 

S. Živanović * 

* Author unable to attend conference.
 

91
 

University of Sheffield 

Vibration Exposure in Offices: A Case Study 104 

J. Starkman 

Midwestern University 

The Determination of Osteogenic Frequencies Related to 

the Osseointegration of Implanted Devices 

106 

T. Lutz 

Wacker Neuson SE 

Vibration Guidelines: Overregulation in Europe Puts 

Unjustified Burden on the Construction Industry 

108 
 

EFFECT OF AN fMRI-COMPATIBLE PIEZOELECTRIC VIBRATION ACTUATOR
 

ON RAT TAIL SKIN PERFUSION 

Danny Riley, Sandya Govindaraju, Chris Zahm, and Keisha Rogers
 

Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 


Milwaukee, WI
 

Introduction 

Vibration of the extremities causes immediate vasoconstriction. This is well documented 

in both human and animal models [Bovenzi et al. 1995; Okada 1986]. In the rat tail vibration 

model, tail skin perfusion fell 37% when exposed to 60 Hz vibration for 5 min [Curry et al. 

2005]. The vasoconstrictive response to vibration has been attributed to activation of the somatosympathetic pathway in response to stimulation of pacinian vibroreceptors in the skin [Ekenvall 

and Lindblad 1986; Olsen 1990; Stoyneva et al. 2003]. The somatosympathetic response is 

hypothesized to be mediated within the rostroventrolateral medulla in the central nervous system, 

but direct evidence is lacking [Ganong 1999]. 

Functional magnetic resonance imaging (fMRI) detects elevated neuronal activity by 

the BOLD signal from radiofrequency impulses perturbed by increased blood flow in a highintensity magnetic field environment. Evidence for or against the involvement of the somatosympathetic system in vibration-induced vasoconstriction can be demonstrated by fMRI of the 

rostroventrolateral medulla during finger vibration exposure. 

Traditional vibration motors are made of ferrous materials and cannot be used for 

fMRI because they are strongly attracted to the MRI magnet. To address this problem, an MRIcompatible vibration actuator was developed by Dynamic Structure and Materials (DSM), 

Franklin, TN (Figure 1). 

 

 

 

 

Figure 1.—The MRI-compatible flextensional piezoelectric actuator is 

constructed of titanium and sheets of piezoelectric material (black 

arrow) that bend in response to applied voltage to cause vertical trans

lation of the lever arm platform. 

Using the rat tail vibration model, the present study sought to determine 

whether the piezoelectric vibration actuator produces a decrease in skin perfusion similar to our 

B&K vibration motor (model 4809, Bruel & Kjaer North America, Norcross, GA) [Curry et al. 

2005]. 

­

Methods 

Sprague Dawley male rats (n=10, 250–300 g) were restrained in tube cages with their 

tails, weighing 6.9 ± 0.1 g, taped to the vibrating platform of the piezoelectric actuator. Blood 

perfusion to the tail skin was measured at the level of tail segment 7 with a laser Doppler flowmeter (Transonic Systems BLF21 monitor, HL-I1047 probe, Ithaca, NY). For each rat, the 

baseline perfusion level was monitored for 5 min before the tail was exposed 5 min to 30 Hz 

92
 
 

 

 

 

 

 

 

vibration of 2 mm peak-to-peak displacement, a calculated 25.1 m/sec2

 rms. Skin perfusion was 

monitored for 30 min postvibration. 

Results 

Tail skin perfusion was decreased by 5 min of vibration and returned to the previbration 

baseline level quickly after vibration ceased (Figure 2). 

0

20

40

60

80

100

120

140

Baseline 0 5 10 15 20 25 30

Time (minutes)

Skin perfusion as % of baseline

**

* Vib

0

20

40

60

80

100

120

140

5

Baseline

0 5 10 15 20 25 30

Post vibration Time (min)

Skin perfusion as % of baseline

**

* Vib

0

20

40

60

80

100

120

140

Baseline 0 5 10 15 20 25 30

Time (minutes)

Skin perfusion as % of baseline

0

20

40

60

80

100

120

140

Baseline 0 5 10 15 20 25 30

Time (minutes)

Skin perfusion as % of baseline

**

* Vib

 

 

 

 

 

 

 

 

0 

20 

40 

60 

80 

100 

120 

140 

Skin perfusion as % of baseline

** 

* Vib 

-5 0 5 10 15 20 25 30 

Baseline Post-vibration Time (min) 

Figure 2.—Tail skin perfusion is plotted as the percentage of the previbration baseline perfusion. The wavy arrow denotes the 5-min period of 

vibration. Tail perfusion was decreased after 5 min vibration. Perfusion 

returned to baseline within 5 min of stopping vibration and remained 

stable. Values are presented as mean ± SEM. (Double asterisk = signifi

cantly different from baseline at p<0.005. Single asterisk = significantly 

different from time 0 at p<0.05). 

­

Conclusions 

The DSM piezoelectric actuator is able to reduce tail perfusion in a manner similar to the 

B&K 4809 motor [Curry et al. 2005]. The actuator seems to be adequate for finger vibration in 

the fMRI environment. 

References 

Bovenzi M, Griffin MJ, Ruffell CM [1995]. Vascular responses to acute vibration in the 

fingers of normal subjects. Cent Eur J Public Health 3 Suppl:15–18. 

Curry BD, Govindaraju SR, Bain JL, Zhang LL, Yan JG, Matloub HS, Riley DA [2005]. 

Nifedipine pretreatment reduces vibration-induced vascular damage. Muscle Nerve 32(5):639–46. 

Ekenvall L, Lindblad LE [1986]. Is vibration white finger a primary sympathetic nerve 

injury? Br J Ind Med 43(10):702–706. 

Ganong WF [1999]. Review of medical physiology. Appleton & Lange. 

Okada A [1986]. Physiological response of the rat to different vibration frequencies. 

Scand J Work Environ Health 12(4 Spec No):362–364. 

Olsen N [1990]. Hyperreactivity of the central sympathetic nervous system in vibrationinduced white finger. Kurume Med J 37 Suppl: S109–116. 

Stoyneva Z, Lyapina M, Tzvetkov D, Vodenicharov E [2003]. Current pathophysiological 

views on vibration-induced Raynaud’s phenomenon. Cardiovasc Res 57(3):615–624. 

93
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

VIBRATION-INDUCED NERVE INJURY AND RECOVERY IN A RAT TAIL MODEL 

Michael A. Loffredo,1 Dennis Kao,1 Ji-Geng Yan,1 Lin-Ling Zhang,1

and Hani S. Matloub1 

1

Department of Plastic Surgery, Medical College of Wisconsin, Milwaukee, WI 

Danny A. Riley,2 

2

Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 

Milwaukee, WI 

Introduction 

Hand-arm vibration syndrome (HAVS), a condition consisting of neurological and vascular dysfunction, is caused by exposure to hand-operated vibration tools. The development of 

HAVS is dose-dependent, with patients clinically presenting with a secondary Raynaud’s phenomenon (vasoconstriction) as well as sensorineural disturbances. Eight million to ten million 

U.S. workers are exposed to vibration tools daily [Curry et al. 2002]. Via a rat tail model, 

we have demonstrated vibration-induced disruption of retrograde axoplasmic transport after only 

two 5-hr long periods of vibration, as well as structural changes to endothelial cells after a single 

4-hr exposure to vibration [Curry et al. 2002; Yan et al. 2005]. The present study was conducted 

to investigate the effect of vibration exposure duration on the disruption of nerve conduction 

velocity (NCV) and the ability to recover nerve function. 

Methods 

Forty-eight male Sprague Dawley rats were randomly assigned to one of six groups, with 

four of eight rats in each group serving as a nonvibrated control. The controls were processed 

and handled identically with the vibrated animals, but their tails were taped to a nonvibrating 

platform. The vibrated rat tails were exposed to linear vertical oscillations of 60 Hz and 5-g 

(49 m/s2) acceleration. The daily duration of vibration was constant at 4 hr/day, and the total 

exposure was either 7 or 14 days. 

Group No. of days 

of vibration 

No. of days 

of recovery 

A 14 60 

B 7 60 

C 14 30 

D 7 30 

E 7 0 

F 14 0 

Rats were then deeply anesthetized with Nembutal. Nerve injury was evaluated electrophysiologically by recording the NCV in the ventral lateral nerve trunk of the tail on the final 

day of recovery, after which the tail segments C5/C6 were harvested for nerve, artery, skin, and 

muscle samples for further analysis. The rats were then euthanized. Animal treatment and surgical interventions were approved by the Medical College of Wisconsin Animal Care Committee 

and complied with the Laboratory Animal Welfare Act. 

Results 

The mean NCV of the control subsets within each group were not different statistically. 

Therefore, we combined all 24 control rats into one group (total control), and the mean NCV of 

this group was 3.95 cm/ms ± 0.21. The mean NCV of the vibrated rats is shown in Figure 1. 

94
 
 

 

NCV in Vibrated Rat Tails

 

 

 

 

3.95 4.25 

2.99 

2.82 2.47 2.62 

3.35 

0 

1 

2 

3 

4 

5 

total contol A vibrate 

(V14R60) 

B vibrate 

(V7R60) 

C vibrate 

(V14R30) 

D vibrate 

(V7R30) 

E vibrate 

(V7R0) 

F Vibrate 

(V14R0) 

NCV (cm/ms) 

Figure 1.—NCV in vibrated rat tails. V14R60 – vibrate 14 days, recover 60 days; V7R60 – vibrate 7 days, 

recover 60 days; V14R30 – vibrate 14 days, recover 30 days; V7R30 – vibrate 7 days, recover 30 days; 

V7R0 – vibrate 7 days, recover 0 days; V14R0 – vibrate 14 days, recover 0 days. Error bars are SEM. 

 

 

 

 

When compared to the total control group, groups A, C, D, E, and F demonstrated a statistically 

significant difference, with groups A, C, E, and F having a P value < 0.001 and group D having a 

P value < 0.05. Group B was not statistically different from the total control group. 

Discussion 

Intense and long duration, hand-transmitted vibration causes a debilitating neurological, 

vascular, and musculoskeletal syndrome known as HAVS. The rat tail model is a valuable tool in 

studying the effects of vibration injury in HAVS because the tail has structural similarities to the 

human hand and digits [Curry et al. 2002]. Prior studies have shown that the NCV of a rat tail 

nerve is significantly reduced after a single 4-hr episode of vibration at 60 Hz and acceleration of 

50 m/s2 [Okada 1986]. The present study demonstrates the effect on NCV after prolonged vibration and, more importantly, displays the ability of the rat tail nerve to recover from 7-day exposure but not 14-day exposure. Vibration for 14 days causes a decrease in NCV that does not 

return to normal after a recovery period of 60 days. Vibration for 7 days also causes a significant 

decrease in NCV, but the injury, although still significant, shows some recovery 30 days postvibration (group D) and complete recovery 60 days following vibration. Our findings suggest 

that 14-day vibration may produce irreversible nerve conduction damage or may require more 

than 60 days to recover. Thus, recovery is a slower process than injury. 

References 

Curry BD, Bain JLW, Yan J-G, Zhang L-L, Yamaguchi M, Matloub HS, Riley DA 

[2002]. Vibration injury damages arterial endothelial cells. Muscle Nerve 25(4):527–534. 

Okada A [1986]. Physiological response of the rat to different vibration frequencies. 

Scand J Work Environ Health 12(4 Spec No):362–364. 

Yan J-G, Matloub HS, Sanger JR, Zhang L-L, Riley DA [2005]. Vibration-induced disruption of retrograde axoplasmic transport in peripheral nerve. Muscle Nerve 32(4):521–526. 

95
 
 

 

 

 

 

 

 

 

 

 

EFFECTS OF VIBRATION EXPOSURE ON ARTERIOLES IN RAT TAIL NERVES
 

Sandya Govindaraju, James Bain, and Danny Riley
 

Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, 


Milwaukee, WI
 

Introduction 

Vasospastic blanching of the fingers and peripheral neuropathy are major complications 

of hand-arm vibration syndrome, an occupational disorder in workers using handheld power 

tools. Our rat tail vibration model was developed to simulate hand-transmitted vibration and 

investigate the cellular mechanisms of vibration injury [Curry et al. 2002]. A single 4-hr 

exposure to 30, 60, 120, and 800 Hz causes arteriolar dilatation and edema in rat tail nerves 

[Govindaraju et al., in press]. A continuous 4-hr bout of vibration at 60 Hz causes cycles of 

vasoconstriction and relaxation in the rat tail artery [Govindaraju et al. 2007b]. Laser Doppler 

monitoring reveals that the rat tail skin undergoes similar cycles of decreased and increased 

perfusion during a 4-hr continuous vibration [Govindaraju et al. 2007a]. The present study was 

designed to test if the arterioles in tail nerves undergo cyclic changes in lumen size during a 4-hr 

exposure to continuous vibration at 60 Hz, 49 m/s2

 (rms) acceleration. 

Methods 

Awake rats were divided into five groups of seven to eight animals per group and 

restrained on a nonvibrating platform with their tails taped to a vibrating stage. Four groups were 

vibrated with a frequency of 60 Hz, peak-to-peak amplitude of 0.98 mm, and an acceleration of 

49 m/s2 (rms) for 5 min, 1 hr, 2 hr, and 4 hr. One group served as a sham control and was treated 

similarly for 4 hr but not vibrated. Following vibration, the tail segment C7 was removed and 

immersion-fixed in 4% glutaraldehyde, 2% paraformaldehyde in cacodylate buffer (pH 7.4). 

Nerves were postfixed in 1.3% osmium tetroxide and embedded in epoxy resin for semithin 

(0.5 μm) sectioning. Version 1.28v ImageJ software was used to measure lumen diameter in 

toluidine blue-stained semithin sections. 

Results 

Immediately following 5 min vibration, the nerve arterioles were significantly (p < 0.05) 

dilated compared to the sham group (Figures 1–2). The 1-hr vibration group had the largest 

lumens. After 2 hr vibration, lumens were comparable to the sham vibration group. At the end of 

the 4-hr exposure, arterioles were again dilated. 

96
 

 

 

Figure 1.—Semithin cross-sections of tail nerves from rats exposed to vibration. Compared to sham, 

arteriole lumens are larger at 5 min, 1 hr, and 4 hr. Lumen size at 2 hr is similar to sham. Bar equals 10 μm. 
0.0

5.0

10.0

15.0

20.0

25.0

30.0

Sham 5 min 1 hr 2 hr 4 hr

Lumen diameter (microns)

* *

*

 

 

 

Lumen diameter (microns)


30.0 

25.0 

20.0 

15.0 

10.0 

5.0 

0.0 

* 

* 

* 

Sham 5 min 1 hr 2 hr 4 hr 

Figure 2.—Comparison of lumen diameters of nerve arterioles. Lumen diameters were significantly 

greater than sham at 5 min, 1 hr, and 4 hr (asterisk indicates p < 0.05). 

 

 

 

Summary and Conclusions 

•	 Nerve arterioles dilate and constrict during continuous vibration exposure. 

•	 This phenomenon is similar to the cycling observed in the rat tail artery and tail skin perfusion, although the cycling is out of phase. 

•	 The presumed cyclic reductions and elevations in blood flow to the nerve during vibration 

may play a role in causing nerve edema and injury. 

References 

Curry BD, Bain JLW, Yan J-G, Zhang LL, Yamaguchi M, Matloub HS, Riley DA 

[2002]. Vibration injury damages arterial endothelial cells. Muscle Nerve 25(4):527–534. 

Govindaraju SR, Bain J, Riley DA [2007a]. Effects of vibration exposure on blood flow 

to the rat-tail skin. In: Proceedings of the 11th International Conference on Hand-Arm Vibration 

(Bologna, Italy, June 3–7, 2007), pp. 239–243. 

Govindaraju SR, Bain JLW, Riley DA [2007b]. Vibration causes ischemia-reperfusion 

injury in the rat-tail artery. FASEB J 21:899.10. 

Govindaraju SR, Curry BD, Bain JLW, Riley DA [in press]. Nerve damage occurs at a 

wide range of vibration frequencies. Int J Ind Ergon. 

97
 
 

 

 

 

 

 

 

 

 

REDUCED SENSORY NERVE THRESHOLDS MAY BE INDICATIVE OF 


NERVE INJURY AFTER REPEATED EXPOSURE TO VIBRATION
 

Kristine Krajnak, G. Roger Miller, Claud Johnson, and Stacey Waugh
 

Engineering and Control Technology Branch, Health Effects Laboratory Division, 


National Institute for Occupational Safety and Health, Morgantown, WV
 

Introduction 

Hand-arm vibration syndrome (HAVS) is characterized by the occurrence of coldinduced vasospasms and a reduction in tactile sensitivity. Although vascular dysfunction usually 

improves after workers stop using vibrating handtools, sensory symptoms are often maintained 

or degrade over time [Nasu and Ishida 1986]. If changes in nerve function could be detected 

earlier, it may be possible to intervene or treat workers and eliminate further damage to the sensory system. The goal of this study was to characterize changes in sensory nerve function during 

a 25-day exposure to vibration in a rat tail model of HAVS. Changes in sensory nerve function 

were assessed using the current perception threshold (CPT) test. 

Methods 

Animals. Male Sprague Dawley rats (6 weeks of age) were housed in AAALACaccredited facilities. All procedures were approved by the NIOSH Animal Care and Use Committee and were in compliance with CDC guidelines for the care and use of laboratory animals. 

Vibration exposures were performed by restraining rats in a Broome-style restrainer and securing 

their tails to the vibration platform. Restraint control animals were treated in an identical manner 

except that the tail platform was set on isolation blocks instead of a shaker. Rats were exposed to 

daily bouts of vibration (4 hr/day, 125 Hz, constant acceleration 49 m/s2

 root-mean-square) or 

restraint for 25 consecutive days. An additional group of animals served as cage control rats. 

These animals were tested at the same times as the other animals, but they were not exposed 

to restraint or vibration. All animals were euthanized with an overdose of pentobarbital 

(100 mg/kg), and tail nerves were collected for 2′-3′ cyclic nucleotide 3′ phosphodiesterase 

(CNPase) immunohistochemical analyses. CNPase levels are positively correlated with glia-axon 

contact in peripheral nerves [Toma et al. 2007]. CNPase staining was assessed in the right ventral nerve bundle (i.e., large nerve) and in smaller nerve bundles (i.e., small nerves less than 

100 μm in diameter) found around the ventral artery. The labeled area of each nerve bundle was 

measured using densitometry (Scion Image). 

CPT tests. Sensory neuron function was assessed by measuring CPTs with a Neurometer 

(Neurotron, Inc., Baltimore, MD). Transcutaneous nerve stimulation was applied to the C10 

region of the tail. Three frequencies were used to test specific fiber types (5 Hz – C; 250 Hz – 

Aδ; and 2,000 Hz – Aβ). The intensity of the stimulus was automatically increased in small 

increments until the rat flicked its tail. Tests at each frequency were repeated until the animals 

displayed two responses that were within 2 CPT (or 0.02 mA) of each other (two to three tests 

per animal). CPT tests were performed after vibration exposure on the first day of each week. 

Data analyses. Sensory nerve thresholds were analyzed using a mixed model three-way 

ANOVA where the independent variables were treatment, days of exposure, and pre/post exposure. Animal served as a random variable for each analysis. Biological data were analyzed using 

a one-way ANOVA where treatment was the independent variable. Differences with p < 0.05 

were considered significant. 

98
 
 

 

 

Results
 

 

 

 

 

Cage 

Sham 

A Vibrated 

A,B A,B 

1 7 14 21 25 

Days of Exposure 

50 10 

2000 Hz CPT (mA) 

8 A,B 

250 Hz CPT (mA)

40 

30 

20 

10 

B B 6 A,B 

4 

2 

0 0

1 7 14 21 25 

Days of Exposure 

Figure 1.—Weekly CPTs in rat tails exposed to 25 days of vibration. Exposure to vibration resulted in a 

reduction in 2,000- and 250-Hz thresholds over time (A: different from cage controls; B: different from day 1 

vibrated, p < 0.05). Restraint controls also displayed lower 250-Hz CPTs than cage controls after 21 and 

25 days of exposure. 

 

 

 

 

 

Area CNPase labeling (μM2) 

Area CNPase labeling (μM2 ) 

* 

* # 

restrained vibrated 

Large Tail Nerve Small Tail Nerves

400 

* # 

30 

20 

10 

0 

300 

200 

100 

0 

cage cage restrained vibrated 

Figure 2.—The area of CNPase immunostaining in large and small tail nerves of rats. CNPase 

immunolabeling was lower in the large, but not small tail nerve bundles of rats exposed to restraint control 

conditions (* less than cage control, p < 0.05; # less than restraint control, p < 0.05). 

Discussion 

•	 CPTs in Aβ fibers (2,000 Hz) decline with repeated exposure to vibration. The reduced 

thresholds of Aβ fibers to stimulation could potentially lead to an increased sensitivity of rats 

to mechanical stimuli and serve as an early indicator of nerve injury. 

•	 Vibrated and restraint control rats displayed reductions in the 250-Hz CPT, indicating that 

changes in Aδ fiber sensitivity are related to restraint and not necessarily due to vibration. 

•	 Vibration-induced reductions in the 2,000-Hz thresholds were associated with a reduction in 

area labeled with CNPase in large and small nerve bundles. A reduction in the density of this 

enzyme shown is associated with reduced glia-axon contact in peripheral nerves and may 

indicate nerve dysfunction [Toma et al. 2007]. 

References 

Nasu Y, Ishida K [1986]. Follow-up study of patients with vibration syndrome in Japan. 

Scand J Work Environ Health 12:313–319. 

Toma JS, McPhail LT, Ramer MS [2007]. Differential RIP antigen (CNPase) expression 

in peripheral ensheathing glia. Brain Res 1137:1–10. 

99
 
 

 

INFLUENCE OF CHANGE IN WORK PRACTICES ON VIBROTACTILE
 

PERCEPTION: PRELIMINARY ANALYSIS OF A PROSPECTIVE STUDY OF
 

FORESTRY WORKERS
 

M. G. Cherniack,1

D. Peterson,1

 N. Warren,1 and T. Morse1 

A. J. Brammer,1,2

1

Ergonomic Technology Center, University of Connecticut Health Center, Farmington, CT 


2

Institute for Microstructural Sciences, National Research Council, Ottawa, Ontario, Canada
 

E. Toppila,3, P. Sutinen,3,

3

Department of Otorhinolaryngology, Tampere University Hospital, Tampere, Finland
 

4

4

Finnish Institute of Occupational Health, Helsinki, Finland
 

5

5

Department of Physical Medicine and Rehabilitation, North Karelia Central Hospital, 


Joensuu, Finland
 

R. Lundstrom,6

6

Department of Biomedical Engineering and Informatics, University Hospital, Umeå, Sweden
 

 T. Nilsson,7 

7

Department of Occupational and Environmental Medicine, Sundsvall Hospital, 


Sundsvall, Sweden
 

G. Neely,8

8

Department of Psychology, Umeå University, Umeå, Sweden
 

Introduction 

The specification of tolerable exposures of the hand to vibration, in particular exposures 

that precipitate few or no neurosensory symptoms, remains a primary goal for occupational 

health standards and regulations. Numbness in the fingers or hands, paresthesias, and a reduction 

in handgrip or difficulty performing fine manipulative tasks are commonly experienced by 

manual workers who operate power tools and have been linked to vibrotactile perception thresholds (VPTs) [Coutu-Wakulczyk et al. 1997]. The purpose of the present work was to apply a 

recently developed metric derived from VPTs to explore the consequences of a change in work 

practices of forestry workers associated with the introduction of mechanical tree harvesting 

(in 1999). The change reduced the exposure to vibration by substituting brush cutters for 

chain saws. 

Methods 

A 13-year prospective study was conducted on a subgroup of an open cohort of forestry 

workers for evidence of work-related changes in hand and arm function. At baseline the subjects 

constituted almost 20% of the open cohort: 28% of the cohort, and subgroup, reported neurosensory symptoms in 1990. The full cohort and subgroup were reexamined in 1995 and 2003. 

The VPTs were determined at the fingertips of digits 3 and 5 of both hands at stimulus frequencies of 4 and 6.3 Hz (believed mediated by the SAI receptors) and 20 and 32 Hz (believed mediated by the FAI receptors) using apparatus complying with ISO 13091-1 (Method A). The 

metric, which has been shown to be applicable to chain saw operators, involves constructing the 

mean change in VPT per receptor population at each fingertip over a time interval of months or 

years, and then summing the threshold changes across the SAI and FAI receptor populations at 

each fingertip [Brammer et al. 2007a,b]. The metric is insensitive to the age of the subject. The 

statistical significance of the observed threshold change is derived from the known threshold 

test-retest repeatability for the apparatus and measurement algorithm. The summed threshold 

changes were formed for the intervals 1990–1995 and 1995–2003, and trends between the values 

for the two intervals were then analyzed. 

100
 
 

 

 

 

Results 

Of the 23 persons (23/124) admitted to the study in 1990, 18 (18/109) returned for 

reexamination in 1995 and 10 (10/59) in 2003. Only one subject (#1) reported neurosensory 

symptoms in 2003. Table 1 shows that of the 20 hands examined on all three occasions, 16 were 

exposed to vibration (subjects #2 and #9 were foremen). 

Table 1.—Trend of summed threshold changes between 1990–1995 

and 1995–2003 

 Subject # 

 1

Age 

 (years), 

2003 

54 

Exposed to 

vibration? 

Yes 

Acuity assessment 

Left hand Right hand 

Conflicting results Deteriorating 

 249 No Improving Improving 

 346 Yes No change Improving 

 455 Yes Deteriorating Deteriorating 

 539 Yes Improving No change 

 639 Yes Deteriorating Deteriorating 

 748 Yes Improving Improving 

 848 Yes Improving Improving 

 951 No No change No change 

10 51 Yes Improving Improving 

Of the 20 hands, 10 were assessed to be 

improving in acuity, 5 deteriorating in acuity, and 4 unchanged. The VPTs from one hand gave 

conflicting results (left hand of subject #1). For the vibration-exposed workers, the trends were 

as follows: eight hands were assessed to be improving in acuity, five deteriorating in acuity, and 

two unchanged. 

Discussion 

The trend in VPTs from the interval before the change in work practices to the interval 

containing the new work practices is encouraging. While not all subjects seem to be benefiting 

from the change in work practices, substantially more exhibit improving sensory acuity than 

deteriorating acuity, and fewer now report neurosensory symptoms. It will be important to follow 

the forestry workers who experience only the new work practices to establish whether or not 

their exposure is below a threshold for the onset of neurosensory symptoms. 

References 

Brammer AJ, Piercy JE, Pyykkö I, Toppila E, Starck J [2007a]. Method for detecting small 

changes in vibrotactile perception threshold related to tactile acuity. J Acoust Soc Am 121(2):1238– 

1247. 

Brammer AJ, Sutinen P, Diva UA, Pyykkö I, Toppila E, Starck J [2007b]. Application of 

metrics constructed from vibrotactile thresholds to the assessment of tactile sensory changes in 

the hands. J Acoust Soc Am 122(6):3732–3742. 

Coutu-Wakulczyk G, Brammer AJ, Piercy JE [1997]. Association between a quantitative 

measure of tactile acuity and hand symptoms reported by operators of power tools. J Hand Surg 

[Am] 22A:873–881. 

This work was supported by the National Institute for Occupational Safety and Health, 

grant U01 OH 071312. 

101
 
INDIVIDUAL VARIABILITY IN CHANGES IN FINGER BLOOD FLOW
 

INDUCED BY HAND-TRANSMITTED VIBRATION
 

Ying Ye and Michael J. Griffin
 

Human Factors Research Unit, Institute of Sound and Vibration Research
 

University of Southampton, Southampton, U.K. 


Introduction 

­

­

­

­

­

102
 

Finger blood flow (FBF) is influenced by many factors, including body temperature and 

hand-transmitted vibration. This study investigated the manner in which the reduction in FBF 

caused by vibration depends on room and finger temperature in individual subjects. 

Methods 

FBF was measured in 12 healthy male subjects in two different room temperatures (20 ± 

1 °C and 28 ± 1 °C) on two separate days, with the order of conditions balanced over subjects. 

FBF was measured using strain gauge venous occlusion plethysmography according to the tech

nique proposed by Greenfield et al. [1963]. A plastic cuff was fitted around the proximal phalanx 

of the left middle finger, with the soft plastic tube from the cuff connected to an HVLab MultiChannel Plethysmograph (University of Southampton, U.K.). A mercury-in-silastic strain gauge 

was placed around the finger at the baseline of the nail. Finger skin temperature (FST) was mea

sured by a k-type thermocouple attached by micropore tape to the distal phalanx of the left 

middle finger. Room temperature was also measured using a k-type thermocouple. 

Subjects lay supine throughout the experiment with both hands supported at heart level. 

After 15 min acclimatization, FBF and FST were measured on the middle finger of the left hand 

every minute while the right hand applied a downward force of 5 N. During the second of two 

10-min periods, the right hand was exposed to sinusoidal 125-Hz vertical vibration at 44 ms−2 

rms (unweighted). 

Nonparametric tests (Wilcoxon matched-pairs signed-ranks test for two related samples 

and the Spearman rank-order correlation) were used in the statistical analysis. 

Results 

The higher room temperature (28 °C) resulted in greater FST (p = 0.001) and greater FBF 

(p = 0.002) than the lower room temperature (20 °C). At both temperatures, FBF reduced during 

vibration (p < 0.001). The absolute reduction in FBF differed between the two room tempera

tures (p < 0.01), but the percentage reduction relative to FBF before vibration was not signifi

cantly different (p = 0.436). 

For each subject, Figure 1 shows the median FBF during the 10-min periods before and 

during vibration with the room temperature at 20 °C and 28 °C. Subjects with a high FBF before 

vibration show greater absolute reduction in FBF during vibration. 

The relation between the median individual FBFs before and during vibration at both 

room temperatures is shown in Figure 2. The percentage reduction in FBF caused by vibration is 

similar in all cases, even though subjects have different FBFs due to individual factors and dif

ferent room temperatures. 
 

 

 

 

 

 

 

 

 

 

 

0 

0.5 

1 

1.5 

2 

2.5 

FBF (ml/100ml/s) 

1 2 3 4 5 6 7 8 9 10 11 12 

Subject 

Figure 1.—Individual median FBF during 

10 min in unexposed left finger before and during vibration of right hand. Open diamond = 

before vibration (20 °C); solid diamond = during 

vibration (20 °C); open triangle = before vibration 

(28 °C); solid triangle = during vibration (28 °C). 

 

 

 

0 

0.5 

1 

1.5 

2 

2.5 

FBF d u rin g v ib ratio n (m l/1 0 0 m l/s) 

0 0.5 1 1.5 2 2.5 

FBF before vibration (ml/100ml/s) 

Figure 2.—Individual median FBF before and 

during vibration. Diamond = 20 °C; triangle = 28 °C. 

During vibration, the variability in FBF (standard deviation measured over 10 min) was 

correlated with the mean FBF (p < 0.001 at 20 °C; p < 0.001 at 28 °C). The coefficient of 

variation in FBF within individuals during vibration at 28 °C was significantly greater than at 

20 °C (p = 0.014), but with no correlation in the coefficient of variation between temperatures 

(p = 0.796). 

The FST was correlated with FBF before vibration (p < 0.001 at 20 °C; p < 0.001 at 

28 °C), but not during vibration (p = 0.093 at 20 °C; p = 0.067 at 28 °C). At 20 °C and 28 °C, 

FBF and FST before vibration were correlated with FBF and FST, respectively, during vibration 

(p < 0.005). 

Before and during vibration, both FBF and FST were correlated between 20 °C and 28 °C 

(FBF-before: p < 0.001; FST-before: p = 0.006; FBF-during: p = 0.046; FST-during: p = 0.037). 

Conclusions 

Individual FBF is influenced by many factors, including room temperature, finger temperature, and hand-transmitted vibration. Increased room temperature and increased finger temperature increase FBF. Hand-transmitted vibration seems to produce a reduction in FBF that is 

proportional to the absolute FBF. 

Reference 

Greenfield ADM, Whitney RJ, Mowbray JF [1963]. Methods for the investigation of 

peripheral blood flow. Br Med Bull 19:101–109. 

103
 
 

 

 

 

 

 

 

VIBRATION EXPOSURE IN OFFICES: A CASE STUDY 

Stana Živanović and Aleksandar Pavić
 

Department of Civil and Structural Engineering, University of Sheffield, Sheffield, U.K.
 

Introduction 

Buildings are constantly exposed to various kinds of vibration during their lifetime (such 

as traffic, ground-borne vibration, wind, and human-induced vibration). Typical receivers of 

these vibrations are humans occupying the structure. Apart from guidelines devoted specifically 

to human response to vibration [BSI 1992], there are vibration serviceability design guidelines 

for floor structures (such as those published by the U.K. Concrete Society [Pavić and Willford 

2005]) that define vibration limits depending on the intended use of the structure (hospital 

operating theaters, residential buildings, offices, or workshops). Civil engineers typically prefer 

to use guidelines linked to the design of buildings rather than those devoted exclusively to vibration perception because of simplicity of the former and unfamiliarity with the latter. 

Data related to in-service vibration of a building are valuable, but are rare. This abstract 

presents such data from 1 day of monitoring of vertical vibration (generated by human walking) 

of an office building floor. The collected data were processed to calculate the vibration measures: vibration dose value (VDV), root-mean-square (rms), and R factor. These are discussed in 

the context that the office floor was subject to complaints due to its excessive vibration during 

normal occupancy. 

Description of Building and Monitoring Process 

The building investigated contains offices. On one of its suspended floors, adverse comments about vibration had been reported by the occupants, especially at a particular work station. 

The vertical acceleration level generated by people walking on the floor during their normal 

work activities was measured by a piezoelectric accelerometer placed close to the work station. 

The accelerometer and the acquisition PC (controlled remotely) were hidden in the false floor; 

therefore, the office staff was not aware of their presence or position. 

Results 

The acquired acceleration was measured during 12 hr and weighted using the Wb weighting curve [BSI 1992]. The eight working hours (9.00 a.m.-5:00 p.m.) of the weighted record 

were extracted (Figure 1a). 1s rms trend is presented in the same figure. 1s rms trend was divided 

by the base acceleration level of 0.005 m/s2

 to obtain response factors (or R factors). R factors 

are typically used for vibration serviceability assessment of buildings; for office buildings, the 

maximum R factor should not exceed a value of 4 [Pavić and Willford 2005]. Figure 1b shows 

that, for the data analyzed, R factor exceeds this value very rarely (only 0.7% of the total time). 

Since people complained about the in-service vibration, this limiting value might not be 

appropriate. 

In contrast with the serviceability guideline, BS 6472 [BSI 1992] requires evaluation of 

vibration using the VDV if the crest factor is above 6. To calculate the crest factor and to study 

the vibration dependence on exposure time, the rms acceleration for different time windows was 

calculated first (Figure 1c). The value stabilized around 0.0066 m/s2

 only when the observation 

time was longer than 100 min. By dividing the corresponding peak acceleration by the rms value, 

the dependence of the crest factor on observation time was obtained as well (Figure 1d). This 

value varied depending on observation time, suggesting that choice of evaluation time should be 

104
 
made carefully. However, in this case, the crest factor was always greater than 6 except for very 

small time windows. Therefore, the VDV should be used to evaluate the human response [BSI 

1992]. During eight working hours, this value reached 0.146 m/s1.75. However, no VDV limit for 

an office building is defined in the current guidelines. 

0.10 1.0 

Acceleration [m/s ]2 

0.05 

0.00 

-0.05 

Nonexceedance probability 

0.8 

0.6 

0.4 

0.2 

0.0 

-0.10 

-0.15 

0 1 2 3 4 5 6 7 8 0 1 2 3 4 5 6 7 8 

Time [h] Response factor (a) (b) 

14 16 

14 

x10-3

RMS acceleration [m/s ]2

12 

12 10 

8 

6 

Crest factor 10 

8 

6 

4 4 

2 2 

0 100 200 300 400 500 0 100 200 300 400 500 (c) Time window [min] (d) Time window [min] 

 Figure 1.—(a) 8-hr weighted time history; (b) cumulative probability of response factor; 

(c) rms acceleration; (d) crest factor as a function of time window. 

Discussion 

 Based on in-service vibration monitoring in an office building (subject to complaints 

about its vibration level), it was found that the current vibration limit of R=4 is probably set too 

high. BS 6472 suggests that the VDV should be used for evaluating measured type of vibration 

rather than the R factor, but it does not define the VDV limit for an office building. This suggests 

that additional research in the field is required to help civil and structural engineers design build

ings against excessive vibration induced by human walking. 

References 

 BSI [1992]. Guide to evaluation of human exposure to vibration in buildings (1 Hz to 

80 Hz). London: BSI British Standards. BS 6472:1992. 


 Pavić A, Willford M [2005]. Vibration serviceability of post-tensioned concrete floors. 


In: Post-tensioned concrete floors – design handbook. 2nd ed. Technical report 43. Surrey, U.K.: 

The Concrete Society, pp. 99–107. 


105 

­
 

 

DETERMINATION OF OSTEOGENIC FREQUENCIES RELATED TO THE 

OSSEOINTEGRATION OF IMPLANTED DEVICES 

Joseph Starkman,1

1

Midwestern University, Chicago College of Osteopathic Medicine 

 Farid Amirouche,2

2

University of Illinois at Chicago, Department of Bioengineering 

and Mark Gonzalez3 

3

University of Illinois at Chicago, Department of Orthopaedic Surgery 

Summary 

­

­

­

The goal of this research is to identify frequencies of vibration that promote the develop

ment of bone in-growth as it relates to the stability of implanted devices such as those found in a 

total hip arthroplasty. There are both therapeutic and harmful levels of vibrations that affect the 

human body. Noxious levels of vibration are considered by frequency measured in hertz, magni

tude measured in g-force, and duration of exposure. Pathological responses are known to occur at 

high frequencies (5–100 Hz) and large magnitudes (>1 g). When vibration is experienced, rela

tively low-peak g levels can be severely damaging if they are at the resonant frequency of organs 

and connective tissues [BME at Stony Brook 2006]. There are no data to suggest noxious effects 

in the 15–50 Hz range at 0.56 g. The ISO standard is 0.8 g at 20–50 Hz for no more than 0.5 hr. 

Recent whole-body vibration therapy (WBVT) devices involve subjecting stationary individuals 

to vibrating platforms at certain frequencies and amplitudes of forced vibrations (Figure 1).

Figure 1.—Oscillating versus vertical vibrating plates. 

 One 

recent study used frequencies of 35–40 Hz and 2.28–5.09 g. The results showed vibration train

ing improved isometric and dynamic muscle strength and increased bone mineral density (BMD) 

of the hip compared to control groups [Verschueren et al. 2004]. 

­

Suboptimal long-term stability of total hip arthroplastic devices has been attributed to 

poor bone in-growth into acetabular components (i.e., osseointegration) mainly due to insufficient subchondral vascular supply [Morscher et al. 2002]. Various improvements in materials 

and surgical approaches have led to increased stability of acetabular components over the years, 

but long-term stability remains an issue. Rapid fluid flow along with the effects of piezoelectricity and streaming potentials affect bone cellular processes in the relative absence of 

significant mechanical loading. For example, tiny acceleratory motions of 0.3 g at 45 Hz for 

10 min/day have been shown to sufficiently influence bone formation and bone morphology 

[Garman et al. 2007]. Given the recent data that tiny acceleratory motions independent of direct 

loading of the matrix have been shown to be anabolic to skeletal tissue and that vascular-induced 

106
 
 

 

 

 

 

 

 

 

interstitial fluid flow (IFF) is known to be continuously present regardless of mechanical loading 

[Hillsley et al. 1993], it is theorized that nonmechanical loading mechanisms and vascular IFF 

play a larger role in bone remodeling than previously thought. Non-load-bearing experiments 

involving the use of pulsed electromagnetic field (PEMF) frequencies close to 15 Hz (1 G 

(0.1 μT); electric field strength 2 mV/cm) point toward the involvement of electromagnetically 

induced mechanisms that significantly contribute to osteogenesis [Massari et al. 2006; Chang et 

al. 2004]. It is hypothesized that combined therapy using vibration devices and PEMFs stimulate 

osteogenesis through enhancement of piezoelectric, streaming potential and other fluid regulatory forces within collagenous structures. The alleviation of soft tissue restrictions improves 

muscle tone, increases bioelectric signals between cells, and promotes greater IFF among cells. 

Improvement of the communication between cells via restoration of bioelectric conduction 

improves the inherent cellular processes and leads to greater bone stability. It may also lead to 

better in-growth of implanted materials. 

The exact frequencies and amplitudes that stimulate therapeutic levels of vibration (e.g., 

improved BMD and bone in-growth of acetabular components) without causing long-term cellular damage or damage to implanted devices are not known and require further investigation. This 

research aims to discover the osteogenic frequencies and develop a method of controlled application of such vibrations. Eventually, therapeutic protocols implementing various osteogenic frequencies (i.e., both PEMF frequencies and WBVT) to rehabilitation therapies for acute and 

chronic bone-involving conditions (e.g., fractures and osteoporosis) may be developed from this 

research. 

References 

BME at Stony Brook [2006]. Contraindications and potential dangers of the use of 

vibration as a treatment for osteoporosis and other musculoskeletal diseases. Stony Brook, 

NY: Department of Biomedical Engineering, Stony Brook University, January 11, 2006. 

[http://www.bme.sunysb.edu/bme/people/faculty/docs/crubin/safety-1-11-06.pdf ]. Date 

accessed: May 2008. 

Chang WH, Chen LT, Sun JS, Lin FH [2004]. Effect of pulse-burst electromagnetic field 

stimulation on osteoblast cell activities. Bioelectromagnetics 25(6):457–465. 

Garman R, Gaudette G, Donahue LR, Rubin C, Judex S [2007]. Low-level accelerations 

applied in the absence of weight bearing can enhance trabecular bone formation. J Orthop Res 

25(6):732–740. 

Hillsley MV, Frangos JA [1993]. Bone tissue engineering: the role of interstitial fluid 

flow. Biotechnol Bioeng 43(7):573–581. 

Massari L, Fini M, Cadossi R, Setti S, Traina GC [2006]. Biophysical stimulation with 

pulsed electromagnetic fields in osteonecrosis of the femoral head. J Bone Joint Surg Am 

88(Suppl 3):56–60. 

Morscher EW, Widmer KH, Bereiter H, Elke R, Schenk R [2002]. Cementless socket 

fixation based on the “press-fit” concept in total hip joint arthroplasty (in German). Acta Chir 

Orthop Traumatol Cech 69(1):8–15. 

Verschueren SM, Roelants M, Delecluse C, Swinnen S, Vanderschueren D, Boonen S 

[2004]. Effect of 6-month whole body vibration training on hip density, muscle strength, and 

postural control in postmenopausal women: a randomized controlled pilot study. J Bone Miner 

Res 19(3):352–359. 

107
 
 

 

 

 

 

 

 

 

 

VIBRATION GUIDELINES: OVERREGULATION IN EUROPE PLACES
 

AN UNJUSTIFIED BURDEN ON THE CONSTRUCTION INDUSTRY
 

Michael Fischer1

1

Wacker Neuson SE, Munich, Germany 

and Todd Lutz2 

2

Wacker Corp., Menomonee Falls, WI 

Introduction 

With a cost of several hundred million euros per year, European Directive 2002/44/EC 

places an unjustified burden on the European construction industry. Equipment owners are 

forced to rate the vibration dose for every employee. In Germany, approximately 90,000 small 

construction businesses are affected, many with fewer than 20 workers. A basic issue with European legislation is that through national transformation laws, regulations can become more 

restrictive. For example, in Germany the whole-body vibration (WBV) limit for the z direction 

was reduced from 1.15 to 0.8 m/s2

. Industry’s concerns that there is no justification behind such 

a change were not taken into account, and the basic goal of European harmonization is in danger. 

During the last decade, the number of occupational diseases has continually decreased through 

industry efforts. Thus, it is the position of Wacker Neuson that the vibration guidelines for both 

hand-arm vibration (HAV) and WBV are not necessary and should be modified or abolished. 

Methods 

With respect to worker health and safety, Wacker Neuson gathered statistical data from 

the Berufsgenossenschaften (BG) (institutions for statutory accident insurance and prevention in 

Germany). BG provided detailed data on confirmed cases of occupational diseases for both HAV 

and WBV. With regard to measurements, we are able to record data on our own test stands. 

We have extensive experience in measuring vibratory plates, rammers, breakers, wheel loaders, 

and other tools that are provided for the construction industry. We also took into account literature from highly regarded experts in the field of vibration assessment. 

Results 

For Germany’s construction industry, we asked for official data regarding the number of 

occupational diseases caused by HAV and WBV. For white-finger syndrome, with the help of 

HVBG (federation of commercial professional associations) [Griesmeier-Goller 2005], we found 

only two confirmed cases in 2004, while the trend from prior years showed a constant decrease. 

The same result was found for occupational diseases caused by WBV, where only five cases 

were confirmed in 2004 with a similar trend for prior years. The numbers clearly demonstrate 

that industry’s efforts to reduce HAV and WBV, driven by market requirements, have yielded 

excellent results. No additional regulation is needed to require the end user to follow highly 

bureaucratic evaluation procedures. 

We also question the experimental methods that are used to obtain vibration results. 

For example, with regard to HAV on vibratory plates, we find that the standard measurement 

procedure given in EN 500-4 shows a scatter of ±1 to 2 m/s2

 with increasing size of the compaction device. Schenk and Gillmeister [2004] showed through tests of HAV values for 12 handheld 

construction tools by 18 separate laboratories that data variations occurred for 40%–50% of 

these institutions. In this study, the measurements of the only ISO 9001-certified laboratory were 

108
 
disregarded because the lab’s values deviated too far from the average. If the requirement is 

below 2.5 m/s2

 and 5 m/s2 to overcome the need of daily reporting requirements, then the issue 

of data scatter is critical. A machine measured with, say, 4 m/s2

 by a market surveillance authority (which currently does not exist) could not be rated precisely. The supplier could properly 

claim the HAV to be above 5 m/s2 or below 2.5 m/s2, and nobody can prove the opposite. 

In discussions with health experts (see also Tominaga [2005]), we found that the frequency weighting curve used in HAV measurements is outdated and, as presented at the Human 

Vibration Conference held in Las Vegas, NV, in 2004, its accuracy relative to health issues is 

questionable. For instance, darkness, cold, smoking, and many other conditions can affect whitefinger syndrome, even in the absence of vibration. Subsequent medical studies have demonstrated that the weighting factor used in the standard is weighted toward the perception of vibration, not to the frequencies causing the greatest neurovascular damage. Coupling of the fingers to 

the handgrip is also an issue for both measurement and health assessment [BG 2004]. When one 

rides a bicycle downhill, one does not grip the handlebars as tightly as possible. Instead, one 

grips at a minimal level that feels comfortable and the bike remains controllable. The same is 

true for vibratory plate users. Most often, the operator follows the self-driven machine instead of 

maintaining a tight grip on the handle. 

For wheel loaders, there is no procedure to determine WBV. Statistical determinations of 

WBV on construction sites are listed in ISO Technical Report (TR) 25398, with discussion of 

raising it from the level of a technical report to a standard. By doing this, ISO regards the state of 

the art to be sufficient regarding health and safety of the operator. Obviously no regulation is 

needed, as industry has already demonstrated success with its market-driven efforts in a competitive environment. 

Discussion 

Wacker Neuson takes the position that the European vibration regulation and related 

documents are not necessary and should be revised or abolished. The financial burden on the 

European construction industry is several hundred million euros per year. This expenditure is not 

justified by the limited and even declining number of reported HAV or WBV injuries. Methods 

to measure levels of HAV and WBV are questionable at best, and an industry surveillance 

authority does not exist. Industry, in response to the market, has been the driving force for technical progress regarding the health and safety of the end user. It is recommended that a similar 

arbitrary and inaccurate standard not be established in other countries as was done in the European Community. 

References 

BG (Die gewerblichen Berufsgenossenschaften) [2004]. Report on project No. BGIA 

4098 – Hand-arm vibrations and coupling forces: measurement methods (in German). 

Griesmeier-Goller [2005]. TBG, HVBG, personal communication. November 9. 

Schenk T, Gillmeister F [2004]. Measurement uncertainties of vibration-emitting handheld tools (in German). Düsseldorf, Germany: VDI report No. 1821, pp. 97–114. 

Tominaga Y [2005]. New frequency weighting of hand-arm vibration. Ind Health (Japan) 

43(3):509–515. 

109
 
Session X: Whole-Body Vibration III 

Chair: Alan Mayton
 

Co-Chair: Miyuki Morioka
 

Presenter 

M. Morioka 

University of 

Southampton 

Title 

Dependence of Equivalent Comfort Contours for Vertical 

Vibration of the Foot on Vibration Magnitude 

Page 

111 

M. L. M. Duarte * 

* Author unable to attend conference.
 

110
 

Federal University of 

Minas Gerais 

Combined Effects of Whole-Body Vibration Exposure and 

Noise on Human Temporary Threshold Shift 

113 

P. W. Johnson 

University of Washington 

A Comparison of Whole-Body Vibration Exposures 

Between Low- and High-Floor Buses 

115 

T. Eger 

Laurentian University 

Changes in Seat-Head Whole-Body Vibration 

Transmissibility and Muscle Activity Under Assymetric 

Neck and Trunk Postures 

117 

J. P. Dickey 

University of Guelph 

The Nature of Multiaxis Six-Degree-of-Freedom Vehicle 

Vibrations in Forestry, Mining, and Construction Heavy 

Equipment 

119 
 

 

 

 

 

 

DEPENDENCE OF EQUIVALENT COMFORT CONTOURS FOR VERTICAL
 

VIBRATION OF THE FOOT ON VIBRATION MAGNITUDE
 

Miyuki Morioka and Michael J. Griffin
 

Human Factors Research Unit, Institute of Sound and Vibration Research
 

University of Southampton, Southampton, U.K. 


Introduction 

In transport, at workplaces, and during leisure and domestic activities, vibration is transmitted to the body via the feet, as well as the seat and hands, and can cause discomfort and 

annoyance. To evaluate vibration at the feet, ISO standard 2631-1 (1997) uses frequency weighting Wk, while British Standard 6841 (1987) uses frequency weighting Wb. Frequency weighting 

Wb was influenced by equivalent comfort contours for vibration of the feet at vibration magnitudes equivalent to 10-Hz vertical seat vibration at 0.8 ms−2 root-mean-square (rms) [Parsons 

et al. 1982]. Recent studies suggest that the equivalent comfort contours may depend on vibration magnitude, as with whole-body vibration [Morioka and Griffin 2006]. 

This experiment was designed to determine the effect of vibration magnitude, from the 

threshold of perception to levels associated with severe discomfort, on equivalent comfort contours for vertical vibration at the foot over the frequency range 8–315 Hz. 

Methods 

Twelve males (mean age = 24.9 years, mean stature = 177.1 cm, mean weight = 73.1 kg) 

were exposed to vertical vibration at the foot via a wooden footrest (30.5 by 10.5 mm with 

10° inclination) mounted rigidly to a vibrator (Derritron VP30). 

Subjective magnitudes for the vibration of the foot were determined using the method of 

magnitude estimation. Subjects compared pairs of motions (a reference and a test motion), each 

lasting 2 sec and separated by 1 sec. The reference motion was fixed at 5.0 ms−2 rms at 50 Hz. 

The test motions were randomly selected from a range of frequencies (8–315 Hz in one-third 

octave steps) and a range of magnitudes (0.002–0.126 ms−1 rms velocity in 3-dB steps, but 

limited to 100 ms−2 rms). The task was to assign a number that represented the discomfort of the 

test motion, assuming the discomfort of the reference motion was 100. Absolute perception 

thresholds were also determined for frequencies from 8 to 315 Hz and are reported elsewhere 

[Morioka and Griffin, forthcoming]. 

The relationship between the sensation magnitude, ψ, and the vibration magnitude, φ , 

was determined for each frequency using Stevens’ power law with an additive constant assuming 

no sensation below the perception threshold: 

ψ = k(φ − φ 0 )

n (1) 

where k is a constant, φ 0 is the perception threshold, and n is the rate of change of the logarithm 

of sensation with the logarithm of vibration magnitude. Linear regression was performed using: 

log10ψ = n log10(φ − φ 0 ) + log10 k (2) 

111
 
 

 

 

 

 

Results 

The calculated vibration magnitude, 


φ (in acceleration), is shown as a function of
 

vibration frequency for comfort contours 

equivalent to sensation magnitudes from 25 to 

300 in Figure 1.

 

 

 

100 

200 

300 

Perception 

threshold 

Sensation 

magnitude 

25 

50 

100 

�

Acceleration (ms -2 r.m.s.) 10 

1 

0.1 

0.01 

1 10 100 1000 

Frequency (Hz) 

Figure 1.—Equivalent comfort contours for vertical 

foot vibration at sensation magnitudes from 25 to 300 

(100 is equivalent to 5.0 ms−2 rms at 50 Hz). 

 It can be seen that the shapes 

of the equivalent comfort contours depend on 

the sensation magnitude, reflecting a nonlinear
 

response. With high-sensation magnitudes, the
 

comfort contours are approximately contours
 

of constant velocity. With low-sensation
 

magnitudes, the contours become similar to 

the absolute perception threshold. 

Discussion	 

The equivalent comfort contours for 

vertical vibration of the foot were inverted and 

normalized to a value of unity at 8 Hz and 

then overlaid with the Wb and Wk frequency 

weightings, as shown in Figure 2.

 

 

 

10 

0.01 

Wk 

50 

100 

150 

200 

250 

300 

�

Threshold 

Wb 

Frequency weighting 

1

0.1 

0.1 1 10 100 1000 

Frequency (Hz) 

Figure 2.—Effect of vibration magnitude on frequency 

weightings (inverted equivalent comfort contours 

normalized at 8 Hz). 

 The 

standardized frequency weightings underestimate the discomfort of low-magnitude 

vibration at frequencies greater than about 

30 Hz (or, conversely, overestimate the discomfort caused by frequencies less than 

30 Hz). The magnitude-dependence of the 

equivalent comfort contours means that no
 

single linear frequency weighting provides an
 

accurate prediction of discomfort caused by
 

vibration at the feet over the range of vibration	 

frequencies and magnitudes investigated. 

References 

BS 6841 [1987]. Guide to measurement and evaluation of human exposure to wholebody mechanical vibration and repeated shock. London: BSI British Standards. 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

Morioka M, Griffin MJ [forthcoming]. Absolute thresholds for the perception of foreand-aft, lateral and vertical vibration at the hand, the seat and the foot. J Sound Vibration. 

Morioka M, Griffin MJ [2006]. Magnitude-dependence of equivalent comfort contours 

for fore-and-aft, lateral and vertical whole-body vibration. J Sound Vibration 298:755–772. 

Parsons KC, Griffin MJ, Whitham EM [1982]. Vibration and comfort. III. Translational 

vibration of the feet and back. Ergonomics 25(8):705–719. 

112
 
 

 

 

 

 

 

 

 

 

COMBINED EFFECTS OF WHOLE-BODY VIBRATION EXPOSURE AND NOISE
 

ON HUMAN TEMPORARY THRESHOLD SHIFT
 

M. L. M. Duarte, R. Izumi, M. A. R. Santos, E. B. Medeiros, B. C. Siqueira, 

and L. A. P. de Carvalho 

Federal University of Minas Gerais, Mechanical Engineering Department,
 

Group of Acoustics and Vibration in Human Beings, Belo Horizonte/MG, Brazil
 

Introduction 

The most common combination of physical risks in work environments is noise and 

vibration. The effects of this combination on the health of people have been very little researched 

and understood, especially the effects on hearing. 

Methods 

In this laboratory study, our goal was to check the influence of whole-body vibration 

(WBV) and noise on the temporary threshold shift (TTS) of healthy subjects with respect to the 

limits set by European Directive 2002/44/EC [2002] and ISO standard 2631-1 (1997). A total of 

13 young adult subjects (10 males and 3 females) without any hearing problem and with no history of occupational exposure to noise and/or vibration were used as volunteers (average age of 

23.9 ± 5.6 years, average weight of 70.2 ± 10.8 kg, and average height of 1.75 ± 0.07 m). They 

were submitted to three test conditions: (1) exposure to high sound pressure levels (SPLs) (white 

noise at 100 dBNA for 15 min), (2) exposure to WBV (z-axis, 6 Hz at 2.45 m/s for 18 min), and 

(3) combined exposure to high SPL and WBV under the same conditions as before, but with the 

first starting 3 min after exposure to WBV. The subjects’ hearing was evaluated before each test 

condition using audiometric and distortion product otoacoustic emission (DPOAE) tests [Izumi 

2006; Duarte et al. 2007]. 

Results 

The results of the audiometric and DPOAE exams were used as references for the comparison with the exams performed just after each exposure condition described above. It is 

important to note that the otoacoustic emission results were taken approximately 2 min after the 

exposures. The comparison of the before and after exposure results aimed to investigate the 

occurrence of hearing TTS. The results were analyzed statistically using the nonparametric 

Wilcoxon signed-rank test [Siegel 1975]. 

This statistical test showed that both the audiometric and DPOAE results after the 

exposure to noise were worse than those obtained before the exposure, mainly around the 

3- and 6-kHz frequencies [Izumi 2006]. Such findings are in accordance with previous studies 

[Manninen 1983a,b; Nordman et al. 2000; Strasser et al. 2003]. However, for WBV exposure 

alone, there were no auditory changes in the results, opposing previous studies using different 

methodologies [Manninen 1983a,b]. The combined exposure showed a big difference in the 

before and after tests, proving noxious effect of the exposure on human hearing, but no greater 

than the exposure to noise alone [Izumi 2006]. 

113
 
 

 

 

 

 

 

 

Discussion 

From the results obtained, for WBV alone, there was no significant hearing variation. For 

the tests using high SPL alone, TTS was present at the 0.5- and 8-kHz frequencies, being the 

highest variations for both exams at the 3- and 6-kHz frequencies. For the tests using a combination of high SPL and WBV, similar results to noise alone were observed. Quantitatively, only at 

4 kHz was the TTS small. 

Therefore, for the levels used, the results showed that, in accordance with previous 

studies, noise has significant effects on the TTS of health subjects. However, no effect was found 

due to vibration alone. Moreover, the combination of WBV and high SPL had neither additive 

nor synergic characteristics on TTS. On the contrary, what was observed was a reduction in the 

hearing effects when compared with the exposure effects of noise alone. 

Acknowledgment: This work was developed using funds from Fundação de Amparo à 

Pesquisa do Estado de Minas Gerais (FAPEMIG) under grant TEC932–05. 

References 

Directive 2002/44/EC [2002]. Directive 2002/44/EC of the European Parliament and of 

the Council of 25 June 2002 on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (vibration). 

Duarte MLM, Izumi R, Medeiros EB, de Carvalho LAP, Siqueira BC, Silva WGF, 

Santos MAR [2007]. The influence of whole-body vibration on the temporary threshold shift of 

healthy volunteers. In: Proceedings of the 19th International Congress on Mechanical Engineering (Brasilia, Brazil). Paper 1748. CD–ROM. 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

Izumi R [2006]. Effects of vibration and high sound pressure levels on temporary threshold shift (Thesis, in Portuguese). Belo Horizonte/MG, Brazil: Federal University of Minas 

Gerais, Mechanical Engineering Department. 

Manninen O [1983a]. Simultaneous effects of sinusoidal whole body vibration and broadband noise on TTS2’s and R-wave amplitudes in men at two different dry bulb temperatures. 

Int Arch Occup Environ Health 51(4):289–297. 

Manninen O [1983b]. Studies of combined effects of sinusoidal whole body vibrations 

and noise of varying bandwidths and intensities on TTS2 in men. Int Arch Occup Environ Health 

51(3):273–288. 

Nordmann AS, Bohne BA, Harding GW [2000]. Histopathological differences between 

temporary and permanent threshold shift. Hear Res 139(1):13–30. 

Siegel S [1975]. Estatística não-paramétrica para as ciências do comportamento (Nonparametric statistics for the behavioral sciences). São Paolo, Brazil: McGraw-Hill do Brasil Ltda. 

Strasser H, Irle H, Legler R [2003]. Temporary hearing threshold shifts and restitution 

after equivalent exposures to industrial noise and classical music. Noise Health 5(20):75–84. 

114
 
 

 

 

 

 

 

 

 

 

 

A COMPARISON OF WHOLE-BODY VIBRATION EXPOSURES
 

BETWEEN LOW- AND HIGH-FLOOR BUSES
 

Peter W. Johnson, Jim Ploger, and Ryan Blood
 

University of Washington, Department of Environmental and Occupational Health Sciences,
 

Seattle, WA
 

Introduction 

Bus drivers represent a substantial segment of the U.S. transportation workforce. 

Research has shown an association between exposure to whole-body vibration (WBV) and 

low back disorders. The goal of this study was to compare and determine whether there were 

differences in vibration exposures between a low- and high-floor bus. High-floor buses require 

the rider to ascend steps (typically three) to reach the seating level. In low-floor buses, the rider 

steps directly on the bus and does not have to climb any steps. For accessibility and efficiency in 

passenger loading and unloading, low-floor buses are becoming the standard in larger metropolitan areas. Older high-floor buses predominate in many fleets, and in order to fully amortize 

the cost of the buses, cities are required to keep these buses in service for at least 15 years. As a 

result, both bus types will be in use as metropolitan companies transition from a predominantly 

high- to a low-floor bus fleet. 

Methods 

The study comprised 25 participants: 15 drove a high-floor bus and 10 drove a low-floor 

bus. The high-floor bus (Gillig Corp., Hayward, CA), typical of somewhat older coach buses, 

was a 7-year-old, 12.2-m bus with a USSC ALX3 seat. The low-floor bus (New Flyer Industries, 

Inc., Winnipeg, Manitoba, Canada), typical of newer coach buses in a bus fleet, was a 4-year-old, 

12.2-m bus equipped with a new USSC Q91 seat. All participants drove their respective bus for 

approximately 1 hr over a 65-km standardized test route. The buses were driven under identical 

load conditions with just the driver (no passengers) on board. The standardized test route 

included surface streets, freeways, and a small section of road containing eight 4-m speed 

humps. This route was chosen to represent different types of driving, including start-and-stop 

driving associated with surface streets, impulsive speed hump excursions, and continuous freeway travel. 

The instrumentation developed for this study included a PDA-based portable WBV data 

acquisition system, which collected raw unweighted WBV data at 640 Hz, and the associated 

MATLAB and LabVIEW software to analyze WBV exposures, per ISO 2631-1 and 2631-5. 

Using the serial port on the PDA, global positioning system (GPS) data were also collected and 

integrated with the WBV exposure data to facilitate the identification of the location (road type) 

and speed of the bus. The preliminary analysis was focused on analyzing the Z-axis measurements of Aw, vibration dose value (VDV), crest factor, maximum continuous peak, and positive 

and negative raw weighted peaks. The crest factor was calculated by taking the maximum instantaneous weight peak value encountered during the route and dividing by the Aw for the route. 

All parameter calculations were identical for the high- and low-floor buses. Data are presented 

as mean and standard error with significance accepted for p-values less than 0.05. 

115
 
 

Results 

The GPS data indicated that there were no significant differences in bus speeds between 

the two bus conditions. Table 1 shows the preliminary results of the analysis of time-weighted 

average and peak data between the two bus types and between the bus seat and floor.

Table 1.—Mean and standard error Z-axis vibration measures by location and bus type (n = 10) 

Seat Floor 

Low-floor High-floor Low-floor High-floor p-value p-value (n = 10) (n = 15) (n = 10) (n = 15) 

Aw 0.40 0.49 0.43 0.46 2 < 0.001 0.001 (m/s ) ± 0.02 ± 0.01 ± 0.01 ± 0.01 

VDV 9.54 11.80 12.37 10.54 1.75 < 0.001 < 0.001 (m/s ) ± 0.47 ± 0.30 ± 0.40 ± 0.23 

12.45 12.38 23.73 12.37 Crest factor 0.93 < 0.001 ± 0.50 ± 0.67 ± 2.00 ± 0.53 

Maximum peak 4.71 5.95 9.76 5.53 2 0.005 < 0.001 (m/s ) ± 0.24 ± 0.32 ± 0.76 ± 0.20 

Raw (+) peak 8.48 9.65 55.31 15.17 2 0.28 < 0.001 (m/s ) ± 1.10 ± 0.47 ± 2.68 ± 0.60 

Raw ( −)peak −7.14 −8.89 −64.67 −16.00 2 0.07 < 0.001 (m/s ) ± 0.54 ± 0.67 ± 5.03 ± 1.52 

 When comparing the floor vibration levels between the buses, the magnitude and direction of the difference 

depended on the type of measure. Except for the average root-mean-square (rms) vibration exposure (Aw), all floor vibration measures were greater on the low-floor bus, with the impulsive 

measures (crest factor, maximum peak, and raw weighted peaks) twofold to fourfold higher. 

When comparing the seat vibration levels, except for the average rms vibration exposure (Aw) 

and crest factor, the opposite trend in seat vibration levels was observed. All seat vibration measures were lower on the low-floor bus despite the greater floor vibration levels. 

Discussion 

There were significant differences in the floor-measured vibration between the buses, 

with twofold to fourfold higher impulsive vibration measures in the low-floor bus. The opposite 

trend was seen in the seat; lower vibration levels were measured from the seat in the low-floor 

bus. These differences could be due to differences in seat design and age. The high-floor bus had 

a 7-year-old seat, while the low-floor bus a new seat. However, what is evident from this study is 

that seats on low-floor buses need to be able to attenuate higher-magnitude impulsive exposures. 

The new seat used on the low-floor bus in this study demonstrated that it was effective in attenuating these higher-magnitude impulsive exposures. Additional work with new seats should be 

conducted on high-floor buses to determine if new seats have the same attenuating effect, and 

further analyses should be done to determine whether there are frequency differences in the 

vibrational exposures between the two bus types. 

References 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

ISO [2004]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 5: Method for evaluation of vibration containing multiple shocks. Geneva, 

Switzerland: International Organization for Standardization. ISO 2631-5:2004. 

116
 
 

 

 

CHANGES IN SEAT-HEAD WHOLE-BODY VIBRATION TRANSMISSIBILITY


 AND MUSCLE ACTIVITY UNDER ASSYMETRIC NECK AND TRUNK POSTURES
 

Tammy Eger,1

1

School of Human Kinetics, Laurentian University, Sudbury, Ontario, Canada
 

James P. Dickey,2

2

Department of Human Health and Nutritional Sciences, University of Guelph, Ontario, Canada
 

Paul-Émile Boileau,3

3

Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), 


Montreal, Quebec, Canada
 

and Joan M. Stevenson4 

4

School of Physical and Health Education, Queen’s University, Kingston, Ontario, Canada
 

Introduction 

Previous literature has shown that exposure to whole-body vibration (WBV) can lead to 

the development of low back pain and that nonneutral driving postures have also been linked to 

an increased risk of developing low back pain [Bovenzi and Betta 1994; Schwarze et al. 1998]. 

However, research that examines the combined effect of twisted sitting posture on trunk and 

neck muscle activity and the transmission of WBV up the spine is limited. This study set out to 

determine if seat-head vibration transmissibility and neck and trunk muscle activity were influenced by asymmetric trunk and neck postures. 

Methods 

Twelve volunteer male subjects with no previous history of low back or neck pain were 

exposed to vibration (0.1–20 Hz random noise Z-axis exposure at 0.8 or 1.2 m/s2

) while adopting 

one of six postures (no trunk rotation with 0o, 15o, or 45o neck rotation; 45o trunk rotation with 

15o or 45o neck rotation; and maximal trunk and neck rotation). The postures were selected based 

on observed driving postures of LHD operators [Eger et al., in press]. The subjects sat on a rigid 

seat with no back rest. Muscle activity (EMG) was measured at six locations (right and left lower 

erector spinae (L3), right and left upper erector spinae (T9), left upper trapezius and the left 

sternocleidomastoid), and vibration transmissibility was measured between the rigid seatpan and 

head at the level of the occipital protuberance. Seat-head vibration transmissibility and coherence 

were monitored during each data collection trial with the Brüel & Kjær PULSE vibration 

measurement and analysis system. Every combination of vibration and posture condition was 

repeated twice, resulting in 24 randomized trials per subject. Each posture was held for 90 sec, 

with the first 15 sec without vibration and the last 75 sec with vibration. A custom software 

program was written in LabVIEW V7.1 (National Instruments, Austin, TX) and was used to 

process the EMG data and calculate the seat-head frequency response transfer functions. A general linear model repeated measures analysis of variance was used to determine statistical 

differences. 

Results and Discussion 

Posture had a significant effect on seat-head transmissibility magnitude (Figure 1), and 

there was a significant interaction between posture, vibration acceleration level, and the primary 

resonance frequency for seat-head transmissibility. There was a significant increase in muscle 

activity with an increase in vibration acceleration, and there was a significant interaction between 

vibration acceleration level, posture, and muscle activity in three of the four trunk (right L3, T9, 

and left T9) muscles monitored (Figure 2). 

117
 
 

 

 

 

Frequency (Hz) 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

5 10 15 0 

1 

2 

3 

4 

5 

6 

Seat-Head 

Transmsi sbi ility 

Posture 

(T0N0) 

(T0N15) 

(T0N45) 

(T15N45) 

(T45N45) 

(TmaxNmax) 

20 

Figure 1.—Mean seat-head transmissibility (CSD transfer 2 function) for each posture condition at 1.2 m/s acceleration 

level. The postures are presented in order of increasing spi

nal and neck rotation. 

 

 

 

 

 

 

 

 

 

 

 

0 

2 

4 

6 

8 

10 

12 

14 

1 2 3 4 5 6 

Postures 

Mean

RT9 Normalized EMG 

Figure 2.—Mean normalized EMG shown for 

erector spinae: right T9 level under no vibration 

exposure (diamonds and dashed line), 0.8 m/s2 

rms acceleration level (squares and solid line), 

and 1.2 m/s2 rms acceleration level (triangles 

and dotted line). NOTE: The postures are pre

sented along the horizontal axis in order of 

increasing trunk and neck rotation: P1(T0N0), 

P2(T0N15), P3(T0N45), P4(T15N45), P5(T45N45), 

P6(TmaxNmax). 

­

­

Vibration is more readily transmitted through a rigid structure [Dietrich et al. 1991]; 

therefore, postures that increase the rigidity or stability of the spine will transmit vibration up the 

spine more readily [Mansfield et al. 2006]. The twisted trunk and neck postures (and resultant 

muscle activity increase) in the current study increased spinal stiffness. This likely accounts for 

the increase in transmissibility magnitude observed as the participants moved from the neutral 

posture to the maximally rotated trunk and neck posture. In conclusion, the findings from this 

study indicated that twisted neck and trunk postures influence the biomechanical response of the 

body to vibration. 

Acknowledgment: Funding was provided by the Workplace Safety and Insurance Board 

of Ontario, Canada. 

References 

Bovenzi M, Betta A [1994]. Low-back disorders in agricultural tractor drivers exposed to 

whole-body vibration and postural stress. Appl Ergon 25(4):231–241. 

Dietrich M, Kedzior K, Zagrajek T [1991] A biomechanical model of the human spinal 

system. J Eng Med 205:20–26. 

Eger T, Stevenson J, Callaghan JP, Grenier S, VibRG [in press]. Predictions of health 

risks associated with the operation of load-haul-dump mining vehicles. Part 2: Evaluation of 

operator driving postures and associated postural loading. Int J Ind Ergon. 

Mansfield N, Holmlund P, Lundström R, Lenzuni P, Nataletti P [2006] Effect of vibration magnitude, vibration spectrum and muscle tension on apparent mass and cross axis transfer 

functions during whole-body vibration exposure. J Biomech 39(16):3062–3070. 

Schwarze S, Notbohm G, Dupuis H, Hartung E [1998]. Dose-response relationships 

between whole-body vibration and lumbar disk disease: a field study on 388 drivers of different 

vehicles. J Sound Vibration 215(4):613–628. 

118
 
 

 

THE NATURE OF MULTIAXIS SIX-DEGREE-OF-FREEDOM VEHICLE VIBRATIONS 

IN FORESTRY, MINING, AND CONSTRUCTION HEAVY EQUIPMENT 

James P. Dickey,1

1

Department of Human Health and Nutritional Sciences, University of Guelph, Ontario, Canada
 

Tammy R. Eger,2

and Sylvain Grenier2
 

2

School of Human Kinetics, Laurentian University, Sudbury, Ontario, Canada
 

Michele L. Oliver,3

3

School of Engineering, University of Guelph, Ontario, Canada
 

Paul-Émile Boileau,4
 

4

Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST), 


Montreal, Quebec, Canada
 

Introduction 

Industrial exposure to whole-body vibration is associated with injury and discomfort. 

Certain industries, notably mining, construction, and forestry, involve high levels of vibration 

[Cann et al. 2003; Eger et al. 2006], including complex six-degree-of-freedom (df) vibration 

[Cation et al., in press]. Relatively few field studies have measured 6-df vibration exposures 

[Els 2005]. There is a general lack of awareness about the nature of multiaxis vibration exposures in heavy machinery. The purpose of this study was to evaluate the nature of multiaxis 6-df 

vehicle vibrations in heavy mobile equipment. 

Methods 

Measures of 6-df accelerations from the chassis were determined for load-haul-dump 

(LHD) vehicles, scrapers, and skidders from the Ontario mining, construction, and forestry 

industries. The data were collected during routine operations under actual working conditions. 

Unweighted chassis data were analyzed to determine the 6-df workplace vibration that is transmitted through seats to the workers. 

Six-df vibration sensors were designed using a MEMSense MAG3D sensor. We tested a 

total of 11 LHDs (haulage capacity between 2.7 and 6.1 m3

), 13 scrapers, and 8 skidders (2 cable 

and 6 grapple). All data were sampled at 500 Hz and continuously recorded using a datalogger 

(DataLOG II, Biometrics) for approximately 1 hr per vehicle. The data were divided into successive 20-sec duration blocks, and the unweighted rms amplitude was calculated for each of the six 

vibration axes. Each of the 6 df was described by the mean and standard deviation. In order to 

evaluate the multiaxis nature of the vibrations, the 20-sec vibration exposures were divided into 

33% percentiles (low, medium, and high) for each of the vibration axes. Each of the 20-sec 

vibration exposures was classified into 1 of the 729 possible combinations to describe the prevalence of combinations of multiaxis vibration. 

Results 

The vibration exposures varied among machine operations and type of machine, but 

overall were rather similar among industries (Figure 1). However, the nature of the multiaxis 

vibrations, as illustrated by the ranking of each of the industries, was considerably different 

across industries (Table 1). Although the “medium lateral acceleration, else low” condition 

was ranked fourth overall and occurred commonly in the forestry and construction datasets, 

it occurred infrequently in the mining dataset (ranked 149 of 729). 

119
 
 

 

6.0 

5.0 

4.0 

3.0 

2.0 

1.0 

0.0 

Figure 1.—Multiaxis vibration exposures during routine machine operation 

(rms amplitude, average, and standard deviation). RMS Amplitude (m/s/s; rad/s/s)

Construction 

Forestry 

Mining 

Ax Ay Az Rx Ry Rz 

Vibration Direction 

Table 1.—Four most prevalent combinations of vibrations in ove rall dataset 

and prevalence of these vibrations within each industry 

Description Ranking 

Overall Mining Forestry Construction 

High on all 6 df 

Low on all 6 df 

1

2

 2

 20

 3

 2

 6 

 1 

Medium yaw, else low 

Medium lateral, else low 

3

4 

 1 

149

14 

 1 

35 

22 

 

 

Discussion 

Although the vibration exposures of the individual vibration axes are similar among vehicles in the mining, construction, and forestry industries, the characteristics of the combined 

multiaxial vibration differ substantially. The magnitude and nature of these multiaxis vibrations 

are important for vehicle and seat design. 

References 

Cann AP, Salmoni AW, Vi P, Eger TR [2003]. An exploratory study of whole-body 

vibration exposure and dose while operating heavy equipment in the construction industry. Appl 

Occup Environ Hyg 18(12):999–1005. 

Cation S, Jack R, Oliver M, Dickey JP, Lee-Shee NK [in press]. Six degree of freedom 

whole-body vibration during forestry skidder operations. Int J Ind Ergon. 

Eger T, Salmoni A, Cann A, Jack R [2006]. Whole-body vibration exposure experienced 

by mining equipment operators. Occup Ergon 6(3/4):121–127. 

Els PS [2005]. The applicability of ride comfort standards to off-road vehicles. J Terramechanics 42(1):47–64. 

This project was funded by a grant from the Workplace Safety and Insurance Board (Ontario, Canada). 

120
 
Poster Session 

Chair: Bertrand Valero 

Co-Chair: Kimberly Balogh 

Presenter Title Page 

A. Øvrum *
 

* Also given as oral presentation. 

University Hospital of
 

North Norway
 

Whole-Body Exposure from Heavy Loading Vehicles 

with Different Risk Assessment Outcomes Using 

Recommendations in the ISO-2631 and ISO-8041 

Standards 

50 

B. Valero *
 

University of Illinois at
 

Chicago
 

Ride Comfort Evaluation Using a Three-Dimensional 

Model of a Human Body Focusing on the Lumbar 

Spine Area 

65 

J. Kim *
 

University of Cincinnati
 

Development of a Receptance Method-Based Modeling 

Technique for Finite-Element Analysis of Hand-Arm 

Vibration 

72 

D. Perottino ** 

** Author unable to attend conference.
 

121
 

Polytechnic University of 

Turin 

An Insight Into Using the Tire as an Active 

Suspension in Human Body Vibration Control 

122 

R. E. Larson **
 

Exponent, Inc.
 

Measurement and Evaluation of Vibration Exposure 

for a Kawasaki 80Z III Wheeled Loader 

124 

I. M. Dudnyk **
 

Donetsk National Medical


University
 

Vibration as a Risk Factor and the Need to Prevent 

Vibration Disease Among Miners in the Donets Coal 

Basin 

126 

J. M. Hughes **
 

Johns Hopkins University


Increased Oxidant Production by Endothelial Nitric 

Oxide Synthase in a New Rodent Model of Hand-Arm 

Vibration Syndrome 

128 

I. J. H. Tiemessen
 

University of Amsterdam
 

Development of an Intervention Program to Reduce 

Whole-Body Vibration Exposure at Work Induced by 

Change in Behavior: A Study Protocol 

130 

M. L. M. Duarte **
 

Federal University of
 

Minas Gerais
 

Whole-Body Vibration Exposure Values for Car 

Passengers on Rough Roads: A Focus on Health 

132 

Tammy Eger 

School of Human Kinetics 

ISO 2631-1 and ISO 2631-5: A Comparison of 

Predicted Health Risks for Operators of Load-HaulDump Vehicles 

134 
 

 

 

 

 

 

 

 

AN INSIGHT INTO USING THE TIRE AS AN ACTIVE SUSPENSION
 

IN HUMAN BODY VIBRATION CONTROL
 

Daniele Perottino,1 and Eurelio Soma1 

1

Polytechnic University of Turin, Italy
 

Farid Amirouche,2 Bertrand Valero,2

2

Vehicle Technology Laboratory, University of Illinois at Chicago
 

Introduction 

Earthmoving equipment relies greatly on tires to move heavy loads and work on rugged 

terrain. Tires have for years been the focus point of many analyses, mostly in relation to the 

safety of the vehicles. The vibration transmitted to the operator has in many ways been neglected 

or simply secondary to tire design. Long-term exposure to vibration has been linked for years to 

severe low back pain, especially in the lumbar region [Schwarze et al. 1998]. The primary suspension of most heavy vehicles is the tire. In the case of earthmoving vehicles such as telehandlers, the tire pressure and size are primary factors in the transfer of energy to the cab and 

seat. Thus, the only component limiting vibration to the operator is the tire. 

The focus of the present collaborative study between the Biomechanics Research Laboratory at the University of Illinois at Chicago (UIC) and the Polytechnic University of Turin, Italy, 

is to characterize the material and inertia properties of a typical telescopic vehicle tire in order to 

create a dynamic model of the tire to investigate how design parameters can be controlled during 

a particular task or maneuver. The work combines both the tire as a finite-element dynamic 

model (flexible body) and an intricate human model that can be used to assess the spinal 

response to this tire/suspension mechanism. This research seeks to provide an insight into the tire 

as a primary suspension for vibration control and to evaluate its role in safety and comfort of 

the operator. 

Methods 

A 240- by 120-mm grid was traced on one of the four tires of a telescopic vehicle. A load 

was then applied to the forklift. The load was slowly decreased. The deformation of the grid was 

observed. The same protocol was followed for different pressures inside the tire. 

The experimental data collected were used to validate a finite-element model of the tire. 

The static model includes the geometrical and material nonlinearities of the tire. The finiteelement model was then exported to ADAMS (Automatic Dynamic Analysis of Mechanical 

Systems). A revolute joint was placed at the center of the rim to allow the rotation of the tire. 

The contact between the ground and the tire was made through the contact joint. The ground was 

modeled as a plane element. A contact translational velocity of 20 km/hr was imposed to the 

plane. The displacements of the center of mass were collected for the different pressures 

considered. 

The displacements resulting from the dynamic analysis were applied to the seat of a sitting human body model developed in the UIC Biomechanics Lab. The assumption of a direct 

connection between the displacement of the tire center of mass and the displacement of the seat 

was made. The human body model includes 19 segments and 18 joints. The inertia properties for 

each segment were taken from an anthropometric database. The interaction between the body 

and seat was modeled through spring and damper in parallel, according to the Amirouche et al. 

[1997] model. The characteristics of each joint were tuned in order to match experimental data 

found in the literature about the first human body resonance. A finite-element model of the 

lumbar spine developed at the UIC Biomechanics Lab was used for the combined analysis. 

122
 
 

 

 

Results 

The results showed lower displacement of the operator’s neck when tire pressure is 

decreased. Essentially, a softer tire leads to better comfort if the pressure is adjusted as a function 

of stresses measured at the rim. Thus, a tire can act as an active suspension if pressure can be 

controlled within a certain bandwidth. 

Figure 1.—Human body model and graph of the neck displacement versus time for different pressures. 

Figure 2.—Dynamic tire model (left) and telescopic vehicle (right). 

References 

Amirouche F, Alexa E, Xu P [1997]. Evaluation of dynamic seat comfort and driver’s 

fatigue. Warrendale, PA: Society of Automotive Engineers, Inc., technical paper 971573. 

Schwarze S, Notbohm G, Dupuis H, Hartung E [1998]. Dose-response relationships 

between whole-body vibration and lumbar disk disease: a field study on 388 drivers of different 

vehicles. J Sound Vibration 215(4):613–628. 

123
 
 

 

 

 

 

 

MEASUREMENT AND EVALUATION OF VIBRATION EXPOSURE
 

FOR A KAWASAKI 80Z III WHEELED LOADER 

Robert E. Larson and Dana Hansen
 

Exponent, Inc., Phoenix, AZ 


Introduction 

Measurements of the vibration and impact environment when operating a Kawasaki 

80Z III wheeled loader were made at the Canadian Pacific Classification Yard, Bensenville, IL, 

in January 2004. The health implications of exposure to the measured loader vibration levels 

were evaluated by comparison with the human vibration exposure boundaries given in the appli

cable standards and measurements of peak acceleration levels associated with many common 

daily activities such as walking, climbing stairs, and jogging. 

­

Methods 

To characterize the vibration exposure that a loader operator would experience, the loader 

was instrumented to record acceleration on the operator’s seat and on the floor directly under the 

seat, per ISO standard 2631-1 (1997). The loader was equipped with an air suspension seat and 

ride control feature, although the ride control feature was turned off during all of the testing. The 

speed of the loader was measured with a global positioning system speed sensor to characterize 

the operations being recorded. The loader did not have a bucket attached; rather, it was being 

used for functions such as hauling rail ties and thus had a fork attachment. The loader was driven 

around the yard and used to perform hauling and transit operations at speeds up to 8–9 mph. 

These particular maneuvers were performed to record the vibration level under what was 

described as typical operation in this yard. In addition to this typical operation, measurements 

were also made to characterize some of the extreme conditions that an operator might occasionally experience. This included traveling back and forth across a series of rails, traveling 

parallel to the track with one side’s wheels between the rails, and traveling across a series of 

railroad ties lined up on a roadway. Four categories of activities were evaluated: “driving,” 

“cross rails,” “over ties,” and “tire between rail.” The individual measurements within each 

category were combined for overall exposure level calculations. It should be noted that the 

results presented here do not represent the exposure for wheeled loader activities such as digging 

with a bucket attachment or high-speed operation over rough terrain. 

Results 

The overall weighted root-mean-square (rms) acceleration (Aw) for each of the four 

activities is shown in Figure 1. A guide to interpreting weighted acceleration values with respect 

to health is given in Annex B of ISO 2631-1. A health guidance caution zone (HGCZ) is defined 

to indicate the level of vibration where a health risk could exist. The amount of time for reaching 

the HGCZ for the “driving” runs is 10.6 hr in the direction of vertical vibration, the axis with the 

highest levels of vibration. Using ISO 2631-1 based on an estimated vibration dose value (VDV), 

the time for the “driving” runs to reach the health caution zone is 24.3 hr. Although the “driving” 

runs best represent the exposure that an operator at a rail yard might experience over an extended 

period of time, the cumulative exposure while traversing “cross rails” was also examined. In this 

124
 
 

 

 

case, the vibration in the lateral direction was the highest, resulting in durations of 3.5–4.0 hr
 

before reaching the lower boundary (depending on which time-dependency equation is used).
 

­

­

 

 

Aw RMS [g] 

Longitudinal 

Lateral 

Driving 

Cross Rails 

Over Ties 

Tire Between 

Vertical 

0.00 0.02 

Rail 

0.03 0.05 0.06 0.08 0.09 0.11 0.12 

Acceleration (g) 

Figure 1.—Weighted rms acceleration. 

To evaluate the effect of transient vibration and shock, a VDV was calculated for the 

“driving” runs. The VDVs were 0.38, 0.48, and 0.54 g · s 0.25 in the longitudinal, lateral, and verti

cal directions, respectively. These values are well below the action level of 1.53 g · s 0.25 defined 

in British Standard 6841 (1987), the EU Directive action value of 0.93 g · .25 s 0 , and the EU expo

sure limit of 2.14 g · s 0.25 . The “driving” runs were also evaluated using ISO standard 2631-5 for 

evaluating vibration containing multiple shocks. The resulting values, based on a lifetime of 

occupational exposure, were below the thresholds, indicating that there is low probability of an 

adverse health effect. 

The rail-crossing runs, traversing railroad ties, and traveling with one side between the 

rails represent occasional exposures to isolated impact and vibration events. Therefore, it is 

worthwhile to look at the peak values from these runs and consider the magnitude of these events 

rather than the weighted average values. As seen in Figure 2, the highest acceleration value 

recorded was in the vertical direction while crossing rails (1.51 g).

 

 

A Maximum [g] 

Longitudinal 

Lateral 

Driving 

Cross Rails 

Over Ties 

Tire Between 

Vertical 

0.00 

Rail 

0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 

Acceleration (g) 

Figure 2.—Peak acceleration. 

 The highest longitudinal and 

lateral values were found while traversing the railroad ties (1.28 and 0.96 g, respectively). To put 

the magnitude of these acceleration values in perspective, they can be compared with values that 

have been measured for common daily activities. The acceleration peaks at the base of the lumbar spine associated with walking down stairs or walking fast were found to be approximately 

1.0 g, stepping down a 9-in step was at 1.6–2.2 g, and jogging was found to be in the range of 

1.9–3.9 g. It is clear that many common daily activities create higher peak vertical accelerations 

in the lumbar spine than the occasional vertical transients experienced while operating a loader. 

Discussion 

The vibration exposure experienced while operating a Kawasaki loader in a rail yard was 

found to be well below the HGCZs for continuous activity. The transient and peak levels also did 

not seem to be at a level of concern. The direction of highest acceleration was dependent on what 

activity the loader was being used for, although vertical was highest for transit and hauling 

activities and for unweighted peak acceleration when crossing rail. 

125
 
 

 

 

 

 

 

 

 

VIBRATION AS A RISK FACTOR AND THE NEED TO PREVENT
 

VIBRATION DISEASE AMONG MINERS IN THE DONETS COAL BASIN
 

Igor M. Dudnyk
 

Donetsk National Medical University, Donetsk, Ukraine
 

Introduction 

The extraction and transportation of coal and rock from a mine are achieved with a variety of machinery and processes, which constitute inherent sources of vibration and mechanical 

shock. The effects of a vibratory mining environment on the human body have been documented 

and can lead to occupational illness or vibration disease in miners. Vibration disease is the second leading cause of occupational illness in miners working in the Donets coal basin (Donbass) 

in the Ukraine. One component of the disease, hand-arm vibration (HAV), is experienced by 

miners who extract coal at the working face using picks and by drifters who perform boring and 

blasting activities associated with entry development. Operators of underground locomotives 

experience symptoms associated with the other component of vibration disease—whole-body 

vibration (WBV). 

Methods 

Incidences of HAV and WBV in underground mines were investigated among face workers, drifters, and locomotive operators. The procedures for measuring and analyzing acceleration 

data were conducted in accordance with national and international standards. An index from 

Suvorov et al. [1984] was used to obtain the total vibration dosage experienced by these workers. 

Results 

Exposure levels were measured at the handles of jackhammers used by the miners. Maximum vibration levels of 2.0–2.1 m/s2

 (93–98 dB) were recorded at frequencies from 16 to 63 Hz. 

The occupational exposure limit (OEL) designated for the low- to mid-vibration frequencies is 

the most often exceeded, whereas vibration frequencies in the range of 250–1000 Hz that are 

measured for jackhammers generally do not exceed the OEL. 

The vibration characteristics of two types of jackhammers used by miners were compared 

relative to HAV exposure levels. The MP-2 jackhammer indicated worse results in the low- and 

mid-frequency ranges than a second jackhammer type. However, HAV levels were 

approximately the same at frequencies of 63 and 125 Hz. Drifters are exposed to HAV as they 

drill blast holes and load material during coal excavating operations. Drilling is performed using 

perforators (punchers – model PP54) that are equipped with pneumatic supports. Exposure 

duration from these sources of HAV averages no less than 2 hr per place change. Maximum 

HAV levels were recorded for frequencies from 8 to 31.5 Hz. An exposure level of 1.8 m/s2

 (84 

dB), exceeding the OEL, occurred at a frequency of 16 Hz. 

Besides HAV, drifters (miners loading rock from a rail-mounted loading machine) are 

exposed to WBV. During these duties, the drifter operates the loading machine from a step or 

platform on the machine. Maximum levels of vibration in the frequency range of 2–16 Hz were 

shown to exceed the OEL. Duration for completing this activity is no more than 1 hr. The drifter 

126
 
 

 

 

 

 

 

 

 

 

will occasionally operate the loading machine from ground level (off the machine) to perform 

work in narrow developments and short distances from the terminal end of the railway up to the 

working face. 

Locomotive operators experience WBV as they transport coal and rock out of the mine 

workings via the rail system. Measurements of WBV exposure indicate that the OEL is exceeded 

at certain exposure frequencies. Measurements taken on the floor of the operator deck of an electric locomotive (model АМ-8) show the exposure limit is exceeded by 0.04 m/s2

 (2 dB) at a 

frequency of 2 Hz and by 0.09 m/s2

 (4 dB) at a frequency of 4 Hz. Maximum exposure levels 

were recorded for operators of underground electric locomotives that show the OEL is exceeded 

by 0.04 m/s2

 (2 dB) and 0.09 m/s2 (4 dB) for frequencies of 8 Hz and 16 Hz, respectively. Total 

exposure duration for operators of both types of locomotives is approximately the same and 

varies up to 4 hr for area changes. 

When analyzing the vibration exposure characteristics of the mine machinery investigated, one can draw some general conclusions about the nature of vibration exposures for the 

mining job activities cited above. Devices such as jackhammers and perforators demonstrate a 

vibration described as variable impulsive, as opposed to variable non-impulsive vibration, which 

is associated with borehole drilling. Considering the coal strata characteristics indigenous to the 

central Donbass, it is not necessary for the jackhammer to operate continuously at high force 

levels associated with peak power. Typical jackhammer operation shows forces ranging from 

98 to 147 N. Consequently, HAV exposures influenced by operating the jackhammer at peak 

force levels are not significant. Noteworthy aspects of using the perforator are greater energy and 

frequency of striker impact (1.5 times that of a jackhammer) and the presence of a twisting 

moment during the active period of its operation. 

An element of rail transport and travel includes mechanical vibrations, which are transmitted to locomotive operators through the vehicle seat and floor. During this study, measurements of WBV exposure show potentially harmful levels for miners engaged in coal production 

activities. These circumstances require regulatory oversight that incorporates protective measures 

for mine face workers, drifters, and locomotive operators in order to lower the risks of HAV 

and WBV exposures that can lead to occupational illness or vibration disease among underground miners. 

Concluding Remarks 

Considering the vibratory work environment and associated risk factors for mine face 

workers, the work activities of the drifter pose the highest risk of vibration disease. Thus, it is 

important for mining operations to include a system of preventive measures to lower the risk of 

vibration disease among mine face workers, particularly the drifter. 

Reference 

Suvorov GA, Shkarinov LN, Denissov EI [1984]. Hygienic assessment of occupational 

noises and vibrations (in Russian). Meditsina (Moscow):57–59. 

127
	
 

 

 

 

 

 

 

 

INCREASED OXIDANT PRODUCTION BY ENDOTHELIAL NITRIC OXIDE 

SYNTHASE IN A NEW RODENT MODEL OF HAND-ARM VIBRATION SYNDROME 

Jennifer M. Hughes,1 Sheila Flavahan,1 

and Nicholas A. Flavahan1 

1

Department of Anesthesiology, School of Medicine, Johns Hopkins University, Baltimore, MD 

Oliver Wirth,2 Kristine Krajnak,2 G. Roger Miller,2 

2

Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 

Morgantown, WV 

Introduction 

The predominant vascular symptom of hand-arm vibration syndrome (HAVS) is exaggerated vasoconstriction, or Raynaud’s phenomenon, involving the digital arteries. In a rat tail 

model of HAVS, we previously demonstrated that a single exposure to vibration caused a 

persistent and selective increase in smooth muscle vasoconstriction in the tail artery mediated by 

activation of α2C-adrenoceptors [Krajnak et al. 2006]. The goal of the present study was to analyze the effects of vibration on digital arteries using a new rat model of HAVS. 

Methods 

Paws of rats were exposed to a single period 

of vibration (4 hr, 125 Hz, constant acceleration 49 

m/s2 root-mean-square) using a restraint method that 

maintains contact between the rat paw and a vibrating 

platform (Figure 1). 

 

 

 

 

 

 

Figure 1.—Exposure apparatus showing rat 

restrained in a cone-shaped plastic bag and the 

paw contacting the vibrating platform. 

Shaker

Accelerometer

Sound Attenuating Cubicle

Axis of Displacement

Pole

Stand

Restraint Bag Hook and loop fasteners

Support Rods

Shaker 

Accelerometer 

Sound Attenuating Cubicle 

Axis of Displacement 

Pole 

Stand 

Restraint Bag Hook and loop fasteners 

Support Rods 

 The physical or biodynamic 

response of the paw in this preparation was assessed 

previously using a laser vibrometer. Results showed 

amplification of vibration transmissibility to the paw 

at this frequency compared with vibration at the 

platform. After the rats were euthanized, digital 

arteries were carefully dissected from vibrated and 

nonvibrated control paws and cannulated at both 

ends with glass micropipettes in a microperfusion 

chamber. The chamber was superfused with modified Krebs-Ringer bicarbonate solution, maintained at 37 °C, pH 7.4, and the artery segment was pressurized to a constant transmural pressure 

of 60 mm Hg. The vessel image was projected onto a video monitor, and the internal diameter 

was continuously measured using a video dimension analyzer (Living Systems Instrumentation, 

Burlington, VT) and recorded using a BIOPAC data acquisition system (Santa Barbara, CA). 

Cumulative concentration-effect curves to the α1-adrenoceptor agonist phenylephrine (0.001– 

1 μM) or 5-hydroxytryptamine (5-HT; 0.001–0.03 μM) were generated by increasing agonist 

concentration in half-log increments after the response to the previous concentration had stabilized. Cumulative concentration-response curves to acetylcholine were assessed during a stable 

constriction to phenylephrine (by 30% of baseline). In some arteries, the endothelium was 

mechanically removed, taking care to not damage the underlying smooth muscle. The production 

of nitric oxide (NO) in the digital arteries was determined using the NO-sensitive fluorescent 

probe 4-amino-5-methylamino-2′,7′-difluorofluorescein diacetate (DAF-FM DA). The 

128
 
 

 

 

 

 

 

 

production of reactive oxygen species (ROS) was determined using the H2O2-sensitive 

fluorescent probe 5- (and 6-)chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate (both at 5 

μM). Images were captured using a fluorescent microscope every 10 sec after addition of 

fluorescent probes and compared to baseline levels. 

Results 

In vitro analysis of vascular function demonstrated that constriction of digital arteries to 

phenylephrine or 5-HT was blunted in vibrated arteries (p < 0.05). α2-adrenoreceptor activation 

by the agonist UK14304 did not cause significant constriction of these arteries. Relaxation to the 

endothelium-dependent dilator acetylcholine was not significantly different between control and 

vibrated arteries. Endothelium removal abolished relaxation to acetylcholine. After endothelium denudation, vasoconstriction to phenylephrine or to 5-HT was no longer impaired in 

vibrated arteries. Likewise, the inhibitor of endothelial NO synthase (NOS) N G-nitro-L-arginine 

methyl ester (L-NAME; 100 μM) increased vasoconstriction to phenylephrine or to 5-HT in 

vibrated but not control arteries (p < 0.05) and abolished the vibration-induced depression in 

vasoconstrictor responses. However, the production of NO, as determined using the NO-sensitive 

probe DAF-FM DA was actually reduced in vibrated compared with control arteries (p < 0.05). 

Concomitantly, ROS production, as determined using the H2O2-sensitive probe, was increased in 

vibrated compared with control arteries (p < 0.05). This vibration-induced increase in ROS production was abolished by the NOS inhibitor L-NAME (100 μM) or by the H2O2 inhibitor catalase (1,000 units/mL). Catalase (1,000 units/mL) also increased vasoconstrictor responses to 

phenylephrine or 5-HT in vibrated but not control arteries and abolished the vibration-induced 

depression in vasoconstrictor responses. 

Discussion 

The major findings of the present study were the following: (1) Digital arteries from 

vibrated rat paws demonstrate blunted vasoconstrictor reactivity when compared to controls; 

(2) endothelial denudation or inhibition of endothelial NOS equalized vasoconstrictor responses 

between control and vibrated arteries; (3) vibrated arteries had decreased NO production, but 

increased ROS production compared to control arteries; and (4) the vibration-induced increase in 

ROS production was abolished by inhibition of NOS or by extracellular catalase, which also 

abolished the vibration-induced depression in vasoconstrictor responses. The results suggest that 

vibration causes an uncoupling of endothelial NOS, which promotes the generation of ROS 

rather than NO [Forstermann and Munzel 2006]. The endothelial and NOS-dependent generation 

of ROS results in oxidant stress and diffusion of endothelium-derived H2O2 through the blood 

vessel wall, which depresses vasoconstrictor responses. This early event may be a key step in the 

pathogenesis of HAVS. 

References 

Förstermann U, Münzel T [2006]. Endothelial nitric oxide synthase in vascular disease: 

from marvel to menace. In: Circulation 113(13):1708–1714. 

Krajnak K, Dong RG, Flavahan S, Welcome D, Flavahan NA [2006]. Acute vibration 

increases α2C-adrenergic smooth muscle constriction and alters thermosensitivity of cutaneous 

arteries. J Appl Physiol 100(4):1230–1237. 

129
 
 

 

 

 

DEVELOPMENT OF AN INTERVENTION PROGRAM TO REDUCE WHOLE-BODY
 

VIBRATION EXPOSURE AT WORK INDUCED BY CHANGE IN BEHAVIOR:
 

A STUDY PROTOCOL
 

Ivo J. H. Tiemessen, Carel T. J. Hulshof, and Monique H. W. Frings-Dresen 

Coronel Institute for Occupational Health, Academic Medical Center, University of Amsterdam, 

Amsterdam, the Netherlands 

Introduction 

It has been estimated that 4%–7% of all drivers in some European countries, the United 

States, and Canada are exposed to potentially harmful whole-body vibration (WBV). Long-term 

occupational exposure to WBV is associated with an increased risk of low back pain and disorders of the lumbar spine [Lötters et al. 2003]. Despite this, a recent review revealed that 

literature on successful strategies to reduce WBV exposure in the workplace is scarce 

[Tiemessen et al. 2007]. This review distinguished strategies directed toward (1) (technical) 

design considerations and (2) skills and behavior. The emphasis in recent research has been on 

the first category, although results (especially based on behavioral changes) from the second 

category may be more promising in reducing WBV exposure at work. Therefore, we developed 

an intervention program aimed at reducing WBV exposure in a population of drivers with an 

emphasis on changing the behavior of the driver and the employer. WBV exposure is used as a 

proxy for low back complaints. 

Methods 

We developed an intervention program to change the behavioral aspects toward WBV 

exposure in accordance with the ASE model [De Vries et al. 1998], which is often used in the 

field of health education. This ASE model can be used to explain attitude and attitudinal 

changes. The ASE model differentiates three cognitions: attitude, social influence, and selfefficacy. Our intervention program focused on (1) a participative approach with a role for the 

driver, the employer, and the occupational health professional, and (2) a multifaceted approach 

comprising both design considerations and skills and behavior aimed at WBV reduction, with 

emphasis on the latter category. By increasing knowledge and skills toward changing these determinants, the ASE of both drivers and employers will be positively changed, which in turn will 

have a favorable effect on the level of exposure. 

The WBV exposure of the drivers and the process variables knowledge, attitude, and 

behavior both for the drivers and the employers were assessed with field vibration measurements 

according to ISO 2631-1 and by self-administered questionnaires. Process variables, such as the 

intention to change behavior, impediments in implementing the intervention program, and compliance with the intervention program, were also assessed by the questionnaire. 

130
 
 

 

 

 

 

 

Discussion 

This study entailed the development of an intervention program aimed at reducing WBV 

exposure to drivers at work by inducing a change in behavior or at least an intent to change the 

behavior of the drivers and their employers. The program consisted of (1) an individual health 

surveillance, (2) an informational brochure, (3) an informative oral presentation, and (4) a report 

of the results of the performed measurements of the WBV magnitude. The “care as usual” group 

received care as usual, which consisted only of the informational brochure and the report. 

This type of intervention program has several advantages. First, it may lead to more permanent effects (until the behavior is changed again). This long-term effect might work simultaneously with changes in WBV company policy. Another advantage is that WBV reduction may 

be realized without large investments in money or time. Third, by implementing this type of 

intervention program, not only the drivers bear responsibility for a possible reduction in WBV 

exposure, but the employers also have a specific role because the program implies certain 

changes in WBV company policy. Lastly, this intervention program provides an active, participative approach of implementing preventive measures. This is in accordance with a study by van 

der Molen [2006], who concluded that in the field of occupational health and safety, actively 

implementing preventive measures with a participative component is an important facet of the 

success of an intervention program. 

The near future will show if this intervention program is effective by showing a decrease 

in WBV exposure. A change in attitude or the intention to change one’s attitude toward WBV 

exposure will hopefully contribute to a decrease in WBV exposure for drivers of various vehicles 

and low back pain over the long term. 

References 

De Vries H, Mudde AN, Dijkstra A, Willemsen MC [1998]. Differential beliefs, perceived social influences, and self-efficacy expectations among smokers in various motivational 

phases. Prev Med 27(5):681–689. 

Lötters F, Burdorf A, Kuiper J, Miedema H [2003]. Model for the work-relatedness of 

low-back pain. Scand J Work Environ Health 29:431–40. 

Tiemessen IJH, Hulshof CTJ, Frings-Dresen MHW [2007]. An overview of strategies to 

reduce whole-body vibration exposure on drivers: a systematic review. Int J Ind Ergon 37(3): 

245–256. 

van der Molen HF [2006]. Evidence-based implementation of ergonomic measures in 

construction work [Thesis]. Amsterdam, Netherlands: University of Amsterdam, pp. 165–176. 

131
 
 

 

 

 

WHOLE-BODY VIBRATION EXPOSURE VALUES FOR CAR PASSENGERS
 

ON ROUGH ROADS: A FOCUS ON HEALTH
 

M. L. M. Duarte, E. A. Oliveira, and L. V. Donadon 

Federal University of Minas Gerais, Mechanical Engineering Department,
 

Group of Acoustics and Vibration in Human Beings, Belo Horizonte/MG, Brazil
 

Introduction 

It is important for the safety and comfort of drivers to understand the effects of wholebody vibration (WBV) on their everyday driving activities. The goal of this study was to evaluate, from a health perspective, WBV levels on standard passenger car drivers when driving their 

vehicles over rough road. Some studies have reported on the effects of WBV on the human spine 

[Bovenzi and Hulshof 1999] and on the comfort and health of drivers [Balbinot 2001]. However, 

there is no evaluation procedure (for example, WBV standards) that can adequately determine 

the effects of WBV exposure on humans [Griffin 1990]. 

Methods 

­

­

This laboratory study examined the influence of WBV on the health of typical passenger 

car drivers. The test sample included students who drove a test route featuring different roadway 

surfaces on the university campus. The vehicles investigated differed by make and model. The 

tests were performed according to European Directive 2002/44/EC [2002] (based on ISO 2631-1 

(1997)), which established the exposure action value (EAV) and exposure limit value (ELV) for 

assessing an 8-hr vibration exposure period. 

The test sample of subjects was composed of 12 volunteers—11 students and 1 lecturer 

from the Mechanical Engineering Department of the Federal University of Minas Gerais. Four

teen tests were performed with 14 different vehicles. Two volunteers took part twice in the 

experiments and each drove two different vehicles. Of the different vehicles used, one can be 

described as off-road; the others were regular passenger cars. The vehicles were considered 

representative of those commonly driven in Brazil. No particular vehicle make or model was 

favored over another. Most of the vehicles were considered “compact,” with small-sized engines. 

Information describing both the drivers and the vehicles was recorded for each test. Descriptive 

characteristics for drivers included sex, age, body mass index, and subjective comfort levels 

obtained at the end of the test. Vehicle information included the make, model, production year, 

engine size, suspension (front and rear), transmission (number of gears), tires, number of doors, 

and maximum occupancy. The study results were viewed with regard to other potential influ

encing factors, such as number of vehicle passengers, the presence of heavy objects inside the 

vehicle, noise levels, and vehicle condition (i.e., how well maintained) [Oliveira 2006]. 

The test route included two types of road surfaces (asphalt and parallelepipeds2

 2Parallelepipeds are stones used for paving roads and are so called because of their shape. They are very common 

in small cities and small traffic roads in Brazil as a cheaper way of paving roads. 

) with 

speed restraints (or bumps). The route was considered more severe or “rougher” than normal 

pavements found in the urban community. This allowed for extrapolating the results to less 

severe road surface conditions. In selecting test route conditions, researchers attempted to 

represent the normal driving routes common to all test subject drivers. Moreover, this permitted 

measuring WBV exposure levels that subjects experience on a daily basis. Drivers were not 

132
 
 

 

 

 

 

 

 

 

 

 

 

instructed as to how to drive the test vehicles, except that they operate them in a manner similar 

to their normal driving habits. The tests were always performed in the evening, between 

7:00 p.m. and 9:00 p.m., so that outside temperature did not influence the results. The total 

driving distance for each of the tests was about 3.6 km and lasted a total of 7 min. 

Results 

Weighted root-mean-square accelerations were obtained from measurements in all three 

orthogonal directions using a triaxial accelerometer and a portable analyzer (model Maestro from 

01dB), which included the weighting functions of the ISO 2631-1 (1997) standard. The results 

showed WBV exposure levels in the z direction as the dominant (or worse-case) axis for most of 

the vehicles. The next highest exposure levels were in the x direction. Two vehicles showed the 

y direction as the dominant (or worse-case) axis, and thus WBV exposures were higher than in 

the other (z and x) directions. Moreover, the y-axis exposure levels for these two vehicles 

exceeded the EAV set by European Directive 2002/44/EC [2002]. Nevertheless, none of the 

vehicles exceeded the ELV recommended for an 8-hr exposure period. 

Discussion 

Although the evaluations were performed for 7-min test periods, the results could be 

applied to an 8-hr equivalent exposure period. In this regard, the cars show satisfactory vibration 

isolation for the drivers. For some of the vehicles, however, the results show that the EAV would 

be achieved in less than a 30-min drive. The present study may thus be used as a basis for 

improving vehicle dynamics and seats in passenger cars typically driven in Brazil. 

Acknowledgment: This work was developed using funds from Fundação de Amparo à 

Pesquisa do Estado de Minas Gerais (FAPEMIG) under grant TEC932–05. 

References 

Balbinot A [2001]. Characterization of vibration levels in bus drivers: a focus on comfort 

and health (Thesis) (in Portuguese). Porto Alegre, Brazil: Federal University of Rio Grande do Sul. 

Bovenzi M, Hulshof CT [1999]. An updated review of epidemiologic studies on the 

relationship between exposure to whole-body vibration and low back pain (1986–1997). Int Arch 

Occup Environ Health 72(6):351–365. 

Directive 2002/44/EC [2002]. Directive 2002/44/EC of the European Parliament and of 

the Council of 25 June 2002 on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (vibration). 

Griffin MJ [1990]. Handbook of human vibration. London: Academic Press. 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

Oliveira EA [2006]. Whole-body vibration effects caused by automotive vehicles in 

human beings: a focus on comfort and health (in Portuguese). Belo Horizonte/MG, Brazil: 

Federal University of Minas Gerais, Mechanical Engineering Department. 

133
 
 

 

 

 

 

 

 

 

 

 

 

ISO 2631-1 AND ISO 2631-5: A COMPARISON OF PREDICTED HEALTH RISKS
 

FOR OPERATORS OF LOAD-HAUL-DUMP VEHICLES
 

Tammy Eger,1 and Sylvain G. Grenier1 

1

School of Human Kinetics, Laurentian University, Sudbury, Ontario, Canada 

 James P. Dickey,2

2

Department of Human Health and Nutritional Sciences, University of Guelph, Ontario, Canada 

Introduction 

Operators of load-haul-dump (LHD) mining vehicles are exposed to whole-body vibration (WBV) and shocks during the course of their work [Eger et al. 2006]. ISO standard 2631-1 

(1997) provides guidance on quantifying WBV in relation to human health and comfort. In 2004, 

ISO 2631-5 was established to quantify health effects to the lumbar spine and the vertebral endplates based on seated WBV exposure containing multiple shocks. Few studies have reported 

predicted health risks based on ISO 2631-1 and 2631-5 standards. Johanning et al. [2006] and 

Cooperrider and Gordon [2006] reported low health risks (for locomotive operators) based on 

ISO 2631-5 criteria and higher health risks based on ISO 2631-1 criteria. However, Alem [2005] 

reported higher predicted health risks (for army vehicle operators) according to ISO 2631-5 criteria compared with those based on ISO 2631-1 criteria. Therefore, health risks predicted by ISO 

2631-1 and 2631-5 were compared to determine if the two approaches predicted similar health 

risks for LHD operators. 

Methods 

WBV exposure at the operator/seat interface from 19 LHD vehicles were recorded for a 

minimum of 1 hr (and extrapolated to represent exposure typical of an 8-hr work shift). Field 

measurements of WBV were conducted in accordance with the ISO 2631-1 standard. Health 

risks predicted by the ISO 2631-1 and ISO 2631-5 analysis were compared across the common 

values that could be normalized to an 8-hr equivalent value. Rankings (high, moderate, low) for 

predicted health risks were assigned to each LHD vehicle operator based on health guidance 

caution zone (HGCZ) limits for A(8) and VDVtotal values published in ISO 2631-1 and Sed limits 

and R Factor values established for probability of an adverse health effect as reported in ISO 

2631-5. 

Results 

According to criteria established in the ISO 2631-1 standard, 9 LHD vehicle operators 

were exposed to vibration levels above the HGCZ and 10 were exposed to WBV levels within 

the HGCZ (Figure 1). According to criteria established in ISO 2631-5, 2 LHD operators were 

exposed to vibration that placed them in a category associated with a “high probability” of injury 

to the lumbar spine, 2 were predicted to have a moderate injury risk, and the remaining 15 were 

predicted to have a low probability of injury (Figure 1). 

Discussion 

The ISO 2631-5 standard was established to evaluate vibration exposures with high shock 

content, and vibration signals with crest factor values greater than 9 indicate high shock content 

within a vibration signal. In this study, all the averaged crest factor values recorded in the vertical axis were above 9, and the highest recorded value was over 50. Given these results, it would 

134
 
 

 

 

 

 

 

Sed (MPa)

VDVTotal (ms 1.75)

 

 

 

 

 

 

 

 

 

be logical to conclude that LHD 

operators experience vibration levels 

with high shock content, making an 

ISO 2631-5 analysis important. 

Health risks predicted by the 

ISO 2631-5 standard were generally 

lower than those predicted by the ISO 

2631-1 standard. The boundaries for 

probable health effects reported in 

ISO 2631-5 were established using 

the best guidance at the time; however, they have not been epidemiologically validated. This study 

provides evidence to suggest that the 

ISO 2631-5 boundaries for probable 

health effects could be set too high. 

Further research with other populations is required to determine if 

changes to the standards are required. 

Acknowledgment: Funding 

was provided by the Workplace 

Safety and Insurance Board of 

Ontario, Canada. 

Figure 1.—Comparison of predicted health risks for 19 LHD 

vehicle operators based on VDVtotal values (ISO 2631-1) and 

Sed values (ISO 2631-5). The associated HGCZ boundaries for 

VDVtotal values and HGCZ limits associated with a low and 

high probability of adverse health effects for Sed values are 

shown as shaded regions. 

-

0 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

55 

60 

0 0.2 0.4 0.6 0.8 1 1.2 1.4 

VDVtotal HGCZ 

Sed 

“HGCZ” 

Sed (MPa) 

VDVTotal (ms-1.75) 

References 

Alem N [2005]. Application of the new ISO 2631-5 to health hazard assessment of 

repeated shocks in U.S. army vehicles. Ind Health 43:403–412. 

Cooperrider NK, Gordon JJ [2006]. Shock and impact on North American locomotives 

evaluated with ISO 2631 parts 1 and 5. In: Proceedings of the First American Conference on 

Human Vibration (June 5–7, 2006). Morgantown, WV: U.S. Department of Health and Human 

Services, Public Health Service, Centers for Disease Control and Prevention, National Institute 

for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2006–140, pp. 77–78. 

Eger T, Salmoni A, Cann A, Jack R [2006]. Whole-body vibration exposure experienced 

by mining equipment operators. Occup Ergon 6(3/4):121–127. 

ISO [1997]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 1: General requirements. Geneva, Switzerland: International Organization 

for Standardization. ISO 2631-1:1997. 

ISO [2004]. Mechanical vibration and shock: evaluation of human exposure to wholebody vibration. Part 5: Method for evaluation of vibration containing multiple shocks. Geneva, 

Switzerland: International Organization for Standardization. ISO 2631-5:2004. 

Johanning E, Fischer S, Christ E, Gores B, Luhrman R [2006]. Railroad locomotive 

whole-body vibration study: vibration, shocks, and seat ergonomics. In: Proceedings of the First 

American Conference on Human Vibration (June 5–7, 2006). Morgantown, WV: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and 

Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 

No. 2006–140, pp. 150–151. 

135
 
Index of Authors
 

Adewusi, S.A. 76 

Aledo, V. 65 

Amirouche, F. 21, 65, 106, 122 

Bain, J. 10, 96 

Basista, Z. 45 

Bazrgari, B. 34, 39 

Blood, R. 63, 115 

Boileau, P. É. 57, 76, 117, 119 

Boutin, J. 23, 57 

Bowden, D.R . 19 

Brammer, A.J. 100 

Cherniack, M.G. 100 

Contratto, M.S. 28, 30 

de Carvalho, L.A.P. 113 

DeMont, R. 61 

Dickey, J. 117, 119, 134 

Donadon, J.V. 132 

Dong, R.G. 70, 78, 89 

Du, J.C. 28 

Duarte, M.L.M. 113, 132 

Dudnyk, I. 126 

Eger, T. 117, 119, 134 

Fischer, M. 108 

Flavahan, N. A. 128 

Flavahan, S. 128 

Frings-Dresen, M.H.W. 83, 130 

Girard, S.A. 74 

Goel, V.K. 54 

Gonzalez, M. 106 

Govindaraju, S. 10, 92, 96 

Grenier, S. 119, 134 

Griffin, M.J. 102, 111 

Hancock, R. 54 

Hansen, D. 124 

Hofmann, J. 30, 41 

Holland, C.L. 85 

Holland, J.P. 85 

House, R. 8 

Hughes, J.M. 128 

Hulshof, C.T.J. 83, 130 

Izumi, R. 113 

Jetzer, T. 87 

Jobes, C. 26 

Johnson, C. 98 

Johnson, P.W. 63, 115 

Jurcsisn, J.G. 19 

Kao, D. 94 

Kashon, M 12 

Kasra, M. 34 

Kaulbar, U. 68 

Khokhlov, T. 50 

Kim, H-J. 59 

Kim, J. 72 

Krajnak, K. 8, 12, 98, 128 

Ksiązek, M.A. 45 

Larocque, R. 74 

Larson, R. 124 

Loffredo, M. A. 94 

Lundstrom, R. 100 

Lutz, T. 108 

Maeda, S. 15, 48 

Manno, M. 8 

Mansfield, N.J. 54 

Marcotte, P. 23, 76 

Martin, B.J. 59 

Matloub, H.S. 94 

Mayton, A.G. 21, 26 

McDowell, T.W. 70, 78, 89 

Medeiros, E.B. 113 

Mendes, R. 52 

Miller, G. R. 12, 98, 128 

Miller, R.E. 26 

Morioka, M. 111 

Morse, T. 100 

Mozaffarin, A. 37 

Neely, G. 100 

Nélisse, H. 23, 57 

Nikanov, A. 50 

Nilsson, T. 100 

Oddo, R. 23 

Oliveira, E.A. 132 

Oliver, M.L. 119 

Øvrum, A. 50 

Pankoke, S. 30, 37 

Paschold, H.W. 32, 81 

Patra, S.K. 57 

136
 
Pattnaik, S.P. 72 

Pavić, A. 104 

Perottino, D. 122 

Peterson, D. 100 

Pielemeier, W.J. 43 

Ploger, J. 63, 115 

Pranesh, A. 61 

Rakheja, S. 57, 61, 76 

Riley, D. A. 10, 92, 94, 96 

Rogers, K. 92 

Roy, V. 74 

Santos, M.A.R. 113 

Shibata, N. 15, 48 

Shirazi-Adl, A. 34, 39 

Silva, L.F. 52 

Siqueira, B.C. 113 

Skandfer, M. 50 

Smith, S.D. 19 

Soma, E. 122 

Starkman, J. 106 

Stayner, R. 17 

Stevenson, J. 117 

Striegel, A. 30 

Sutinen, P. 100 

Syurin, S, 50 

Talykova, L. 50 

Tarnowski, J. 45 

Tétrault, S. 74 

Tiemessen, I.J.H. 83, 130 

Toppila, E. 100 

Turcot, A. 74 

Vaktskjold, A. 50 

Valero, B. 21, 65, 122 

Vellani, J. 54 

Warren, C. 70, 78, 89 

Warren, N. 100 

Waugh, S. 12, 98 

Webster, J. 85 

Welcome, D.E. 70, 78, 89 

Wirth, O. 128 

Wölfel, H.P. 41 

Wu, J. 78 

Xu, X. 70, 89 

Yan, J. 94 

Ye, Y. 102 

Zahm, C. 92 

Zhang, L 94 

Ziemiański, D. 45 

Živanović, S. 104 

137
 
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DHHS (NIOSH) Publication No. 2009–145