Received 24 February 2004; accepted 9 March 2004

Available online

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doi:10.1016/j.jsr.2004.03.014

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Journal of Safety Research 35 (2004) 255 – 261

Whole-body vibration and postural stress among operators of construction

equipment: A literature review

N. Kumar Kittusamya,*,

a

Spokane Research Laboratory, National Institute for Occupational Safety and Health, 315 E. Montgomery Ave., Spokane, WA 99207, USA

* Corresponding author.
 

E-mail address: NFK8@CDC.GOV (N.K. Kittusamy).
 

Bryan Buchholzb

b

Construction Occupational Health Project, University of Massachusetts Lowell, One University Ave., Lowell, MA 01854, USA

Abstract

Introduction: Operators of construction equipment perform various duties at work that expose them to a variety of risk factors

that may lead to health problems. A few of the health hazards among operators of construction equipment are: (a) whole-body

vibration, (b) awkward postural requirements (including static sitting), (c) dust, (d) noise, (e) temperature extremes, and (f) shift

work. It has been suggested that operating engineers (OEs) are exposed to two important risk factors for the development of

musculoskeletal disorders: whole-body vibration and non-neutral body postures. Method: This review evaluates selected papers that

have studied exposure to whole-body vibration and awkward posture among operators of mobile equipment. There have been only

few studies that have specifically examined exposure of these risk factors among operators of construction equipment. Thus other

studies from related industry and equipment were reviewed as applicable. Conclusion: In order to better understand whole-body

vibration and postural stress among OEs, it is recommended that future studies are needed in evaluating these risk factors among

OEs.

1. Introduction

Work-related injuries and illnesses pose a continuing

threat to the health and well being of U.S. workers. The

construction industry has been recognized historically as

having higher rates of fatality, injury, and illness than other

industries (Bureau of Labor Statistics [BLS], 1996; McVittie, 1995). In 1994, there were an estimated 218,800 lost

workday injuries in the construction industry (BLS, 1996).

Construction also had the second highest incidence rate for

sprains and strains.

Operating engineers (OEs), also known as hoisting and

portable engineers, operate and maintain heavy construction

equipment, such as cranes, bulldozers, front-end loaders,

rollers, backhoes, and graders. They may also work as

mechanics. The operators use these pieces of equipment to

perform four main tasks: (a) the building of roads, bridges,

tunnels, and dams; (b) the construction of buildings and

power plants; (c) the removal of earth materials and grading

earth surfaces and in the replacement of concrete, blacktop,

and other paving materials; and (d) the constructing of

drainage systems, pipelines, and other related tasks, such

as blasting (Stern & Haring-Sweeney, 1997).

A recent estimate shows that there are currently 540,000

operating engineers in the United States (BLS, 2003; this

estimate does not include mechanics or oilers) who are

exposed to whole-body vibration. A majority of these OEs

(90%) perform excavating and paving work (e.g., operating

dozers, loaders, excavators), while the remaining are crane

operators (10%). Because of the varied duties performed by

OEs, they have the potential for exposure to numerous

hazards that can be episodic in nature. Some of the health

hazards among operators using heavy construction equipment are: whole-body vibration, awkward postural requirements (including static sitting), psychosocial factors, dust,

diesel exhaust, asphalt and/or welding fumes, noise, temperature extremes, time pressure, and shift work (Buchholz,

Moir, & Virji, 1997; Stern & Haring-Sweeney, 1997;

Zimmerman, Cook, & Rosecrance, 1997). Despite the

immediate hazards of the trade, there are few reliable data
256 N.K. Kittusamy, B. Buchholz / Journal of Safety Research 35 (2004) 255–261

that characterize these hazards and their health outcomes.

Thus it is imperative that information be gathered to assist

in designing better working conditions for these workers,

which will enhance their health and well being, productivity, morale, and efficiency in performing their jobs. Pilot

research (Buchholz et al., 1997) has shown that the major

ergonomic exposures among OEs are whole-body vibration,

repetitive arm motions, awkward postures (including static

sitting), and poor seat design. There is a current need to do

research focusing on ergonomic exposure data that might

contribute to the knowledge of the development of musculoskeletal diseases among these operators.

Whole-body vibration (WBV) produces systemic affects

on the entire body. Information regarding the chronic effects

of WBV is still in infancy. However, there is abundant

information regarding subjective responses to vibration.

Some limitations of these studies are that they were performed in laboratory settings and that they only evaluated

sinusoidal vibration, and thus are not representative of reallife conditions. In general, there are not sufficient data

available to characterize the exposures and to better understand the health outcomes among operators of construction

equipment.

Working posture is believed to be influenced by many

factors including workstation layout, location and orientation of work, individual work methods, and the workers’

anthropometric characteristics (Hsiao & Keyserling, 1990;

Keyserling, Punnett, & Fine, 1988). Awkward posture is one

of the important risk factors in the development of musculoskeletal disorders (Chaffin & Andersson, 1984; Keyserling et al., 1988; Putz-Anderson, 1988). Awkward postures

refer to joint positions significantly deviated from the

neutral body postures and may include static positioning

or constrained body postures (twisting or elevated positioning; Putz-Anderson, 1988). Exposure to awkward posture

can result in localized fatigue or pain and contribute to the

development of musculoskeletal disorders. The relationship

between awkward posture and the development of musculoskeletal disorders of the neck, shoulder, and trunk has

been reported recently (National Institute for Occupational

Safety and Health [NIOSH], 1997).

2. Whole-body vibration

In reviewing the literature, a representative sample of

epidemiological papers that studied exposure to whole body

vibration among various populations were selected including, operating engineers (or operators of construction equipment), tractor drivers, and drivers of forklifts and freightcontainer tractors. Most of these studies had a control group

for comparison.

A simple descriptive study by Zimmerman et al.

(1997) provided insight into the specific population of

interest (operating engineers). They investigated workrelated musculoskeletal symptoms among operating engineers (N = 410). There were no control groups used for

comparison. There was a response rate of 38% among the

operating engineers. Work-related musculoskeletal symptoms were greatest in the low back (60%), neck (44%),

shoulders (37%), and knees (32%). Missed work due to

musculoskeletal symptoms was most prevalent in the low

back (8%), ankles/feet (3%), wrist/hands (3%), and shoulder (2%). Physician visits due to musculoskeletal symptoms were highest for the low back (25%), neck (20%),

upper back (13%), and shoulders (12%). Operators with

longer work histories consistently reported greater percentages of symptoms, missed work, and physician visits than

the less experienced group. For all body regions the

percentage of work-related symptoms, missed work, and

physician visits varied greatly among the five different

types of equipment (backhoe, crane, pushcat/dozer, pull

scraper, and end loader). These results are suggestive of

equipment specific demands and stress experienced by the

operating engineers. Operators using older equipment

reported a higher percentage of missed work and physician

visits due to musculoskeletal symptoms than those using

newer equipment, and those using a combination of both

newer and older equipment.

Dupuis and Zerlett (1987) studied 352 operators of earthmoving equipment with at least three years of work experience based on interviews and medical examinations. From

this group, X-rays showing the segments of the spine were

available for 251 operators with at least 10 years of work

experience. This group was compared with a control group

of 315 workers that worked in similar environments with no

vibration exposure. From the control group, X-rays of the

spine were available for 151 workers. In addition, 149

operators of earth moving equipment were asked to rate

their discomfort after exposure to 8 hours of vibration.

Among the 352 operators and 315 referents studied, the

operators reported significantly higher spinal discomfort

during their work shift (75% vs. 49%) and after their shift

(59% vs. 45%), as well as more disorders of the spine (70%

vs. 54%). Furthermore the operators reported significantly

higher discomfort in the lumbar region (69% vs. 42%) than

for the control group. The most frequent (and significant)

health impairment among the operators was lumbar syndrome (81%) and was significantly higher than found in the

control group. The diagnosis of the lumbar syndrome covers

all the symptoms that are caused directly or indirectly by

degenerative lesions of the lumbar disks. The radiological

findings showed morphological changes of the lumbar spine

as a function of age. There was statistically higher prevalence of pathological findings among operators compared

with the control group. After 8 hours of exposure, backache

was reported among 45% of the operators (N = 149). The

prevalence of backache increased from 35% in the younger

group (20 – 29 years) to 67% in the older group (50 – 59

years). The authors concluded that long-term exposure to

whole-body vibrations causes morphological changes in the

lumbar spine.
N.K. Kittusamy, B. Buchholz / Journal of Safety Research 35 (2004) 255–261 257

In a retrospective (10-year) follow-up study, Bongers,

Boshuizen, Hulshof, and Koemeester (1988) compared the

incidence of permanent work disabilities among crane

operators (N = 743) and a control group of ‘‘floor workers’’

(N = 662). It should be noted that 33% of the control group

was exposed to vibration 20% of the work time. Both

groups consisted of male workers. This study demonstrated

that the crane operators were twice as likely to receive

disability pension due to intervertebral disc disease as the

control group. The crane operators with 5 to 15 years of

exposure were at higher risk of disability due to intervertebral disc disorders. When the duration of exposure was

included in their model as a time-dependent covariate, a 1.5

time increase in risk of disability due to intervertebral disc

disorders was found for each 10 years of additional exposure. Since the control group was exposed to some vibration

and there was a potential health-based selection of the index

group prior to the start of the study, it is believed that the

incidence density ratio (IDR) observed in this study are

underestimates of the true IDRs. There may have been some

health-based selection during the observation period that

could also affect the true estimate of the IDRs.

Boshuizen, Bongers, and Hulshof (1992) examined

self-reported back pain among drivers of forklift and

freight-container tractors (N = 196) and a reference group

of non-drivers (N = 107) from six harbor companies (5

trans-shipment companies and a container repair company). The response rates in the index and control groups

were 78% and 83%, respectively. The younger drivers

( < 35 years) reported a higher prevalence of back pain

(58%) than the controls in the same age group (25%). The

older drivers had less prevalence than the younger group.

The lack of effect found among older workers could be

attributed to health-based selection.

Boshuizen, Bongers, and Hulshof (1990a) examined selfreported back pain in tractor drivers exposed to vibration (N

= 450) and a reference group of non-exposed workers (N =

110). There was a 79% response rate in this study. The

workers were classified as being in the index or reference

group according to their vehicle driving history. In general,

the prevalence of back pain was higher among the tractor

drivers and was also higher with an increasing vibration

dose. Total vibration dose was calculated as being equal to

Si a

2

i ti. Where ai is the estimated vector sum of the

frequency weighted root mean square (rms) acceleration in

X, Y, and Z directions (axes) for vehicle i (in units of m/s2

)

and ti is the time duration of driving a vehicle (in units of

full time years). The highest prevalence odds ratio were

found for severe types of back pain, but these prevalence

odds ratio did not increase with vibration dose, which might

have been due to health-based selection.

In an 11-year follow-up study, Boshuizen, Hulshof, and

Bongers (1990b), investigated disability pensioning and the

incidence of the first sick leave of 4 weeks or longer due to

back disorders in a group of drivers exposed to WBV (N =

689) and a reference group of workers exposed to slight or

no vibration (N = 109). The workers were classified as

being in the index or reference group according to their

vehicle driving history. Most of the employees assigned to

the reference group were mechanics and maintenance workers. The drivers used tractors or other highly vibrating

vehicles used in farming. The incidence of long-term sick

leave due to a back disorder was about 50% higher in the

drivers. This incidence seemed to increase with duration of

exposure and vibration dose (dose calculated as described in

Boshuizen et al., 1990a). The tractor drivers were at a higher

risk of being disabled at a younger age than the reference

group. This study provides evidence of an association

between driving tractors and other vibrating vehicles and

long-term sick leave due to back disorders.

Bovenzi and Betta (1994) investigated the occurrence of

low back pain among agricultural tractor drivers (N = 1155)

and a control group of office workers (N = 220). All of the

workers in both groups were males. The response rates

among the tractor drivers and controls were 91% and 92%,

respectively. Age, occupation, vibration exposure, perceived

postural load, and back trauma were found to be the most

important predictors for the occurrence of lifetime, transient,

and chronic LBP for the complete sample. A significant

trend of higher prevalence of lifetime LBP, acute LBP, and

sciatic pain was associated with an increase in total tractor

driving hours. The crude prevalence for back pain and lowback symptoms was consistently greater among the tractor

drivers than the controls. With an increase in total vibration

dose (dose calculated as described in Boshuizen et al., 1990a)

there was a consistent increase in odds ratios for back pain

and low back symptoms in drivers. This study also demonstrated that the duration of exposure was associated more

with LBP compared with vibration exposure magnitude

alone. This is in agreement with Boshuizen et al. (1990a).

Several authors have performed extensive reviews on the

health effects of long-term exposure to whole body vibration (Hulshof & Veldhuijzen van Zanten, 1987; Seidel &

Heide, 1986; Wikstrom, Kjellberg, & Landstrom, 1994). A

summary of these reviews will further help understand the

adverse health effects of WBV, albeit in concert with other

risk factors.

Wikstrom et al. (1994) reviewed 45 health studies in

which index groups exposed to WBV were compared to a

reference group not exposed to WBV. There were also

studies that have made comparison between groups with

different exposure levels. In all, the review covered about

18,000 workers exposed to WBV and around 29,000 control

subjects. In 27 of the studies the combined affect of WBV

and other risk factors was discussed, but only 50% of them

actually studied these factors. Work postures were mostly

considered in the studies, but noise and other stressors have

also been discussed. The following conclusions were advanced from their review:

•	 Cumulative exposure (in years) to WBV may contribute

to injuries and disorders of the lower back.
258 N.K. Kittusamy, B. Buchholz / Journal of Safety Research 35 (2004) 255–261

•	 WBV in combination with awkward posture (including

static sitting) may result in excessive risk of injury and

disorder to the lower back.

•	 An exposure-response relationship cannot be established

at this time.

•	 Disorders of the gastrointestinal system and urogenital

system, especially in women, have been observed in

those exposed to WBV. As such these health effects

warrant further study.

Hulshof and Veldhuijzen van Zanten (1987) performed

an evaluation of 19 epidemiologic studies on the effect of

WBV. In all, this review covered about 17,000 exposed

and 11,000 reference workers. This review was restricted

to the relationship between WBV and symptoms and/or

signs of thoracic and lumbar disorders. A scoring procedure was used to assess the relative quality of the contribution of each epidemiologic study. The evaluative criteria

were: the quality of exposure data, effect (health) data,

study design, and methodology. The most frequently

reported adverse health effects were low back pain, early

degeneration of the spinal system, and herniated lumbar

disc. The results of the scoring procedure indicated that

most of the studies scored relatively low in the assessment.

None of the studies reached a score of more than 50% in

all criteria of evaluation. In spite of the weakness in the

studies, almost all findings in the different studies, particularly the studies with better methodology, demonstrated a

strong tendency in a similar direction, the authors concluded that long-term exposure to WBV can be harmful to the

spinal system. An exposure-response relationship cannot be

established at this time. The main shortcomings of the

epidemiological studies to date were that their description

of vibration exposure, the exposure-time history, and the

contributing occupational environment was not sufficient,

and that the challenge of finding groups that were not

exposed to vibration was not met. The authors suggested

that more epidemiologic research, especially with better

study design and methodology, are needed to understand

the relationship between long-term WBV exposure and

adverse health effects.

Seidel and Heide (1986) performed a critical survey of

the literature (185 articles) to study the long-term health

effects of exposure to whole-body vibration. The review

contains health data on 43,000 workers exposed to wholebody vibration and 24,000 workers in the reference group.

Only a third of the papers contained a measured value for

WBV, while more than 30% did not contain any exposure

data. The authors conclude that workers exposed to seated

vibration equal to or greater than the ISO Exposure Limit

manifested an increased health risk of the musculoskeletal

and peripheral nervous system. With a lower probability,

the digestive system, the peripheral veins, the female

reproductive organs, and the vestibular system were also

affected. On average, the health risk increased with higher

intensity or duration of WBV exposure. However, a

quantitative exposure-response relationship could not be

determined. This review favors changing the ISO limit to a

lower level.

In summary, more musculoskeletal symptoms (specifically relating to the low back) were observed among the

index group(s) than the reference group(s). WBV exposure equal to or greater than the ISO limit can adversely

affect the health and well being of the worker. Also

various studies have shown that many different occupational groups are affected by whole-body vibration. Most

of the studies reviewed indicate that adverse health

effects were also attributed to the combined affect of

awkward posture (including static sitting) in concert with

WBV. As such it is important to measure the postural

requirements of the work, in addition to WBV, when

epidemiological studies are performed and when exposure

characterization is established. Other risk factors should

be evaluated to present a holistic view of the exposure to

the operator.

3. Awkward posture

Awkward posture is another important risk factor observed among operating engineers. The significance of

assessing the postural requirements of operators exposed

to whole-body vibration has been echoed in the recent

literature (e.g., Bongers et al., 1988; Bongers, Hulshof,

Dijkstra, & Boshuizen, 1990; Bovenzi & Zadini, 1992;

Johanning, 1991). But in reviewing the literature it was

found that there are very limited, if any, studies quantifying

awkward postures among operators of heavy construction

equipment. Thus other studies from related industries with

operators using similar equipment will be reviewed as

applicable.

A pilot study by Kittusamy and Buchholz (2001) evaluated postural stress during excavating operations. They

evaluated postural requirements of the operators performing

trench digging operations on two different pieces of construction equipment. For both pieces of equipment, they

found that the trunk was either flexed or twisted for at least

25% of the cycle time. The right shoulders were elevated a

majority of the cycle time and the neck was either flexed or

twisted for at least 22% of the cycle time for operators of

either pieces of equipment.

A study by Bovenzi and Betta (1994), already discussed

in the WBV section of this paper, indicated a linear trend of

increasing prevalence of low back pain (LBP) among tractor

drivers that had an increasing perceived postural load.

Perceived postural load was assessed in terms of frequency

and/or duration of awkward posture at work. Furthermore,

the tractor drivers with excessive WBV and postural stress

had more than a three-fold increased risk for chronic LBP

than the unexposed subjects.

In a recent study, Bovenzi, Pinto, and Stacchini (2002)

investigated the occurrence of LBP among a group of 219
N.K. Kittusamy, B. Buchholz / Journal of Safety Research 35 (2004) 255–261 259

port machinery operators (straddle carrier, fork-lift, and

crane operators) exposed to both WBV and postural load,

and a control group of 85 maintenance workers employed at

the same company. The 12-month prevalence of low back

symptoms was significantly greater in the forklift truck

drivers than in the controls or the other two groups of port

machinery operators. An excessive risk for lumbar disk

herniation was also observed among port machinery operators that had prolonged driving experience. Even though

this cross-sectional study does not allow for definitive

conclusion on the relationship between exposure and low

back disorders, the findings of this investigation provide

additional evidence that suggest that seated WBV exposure

and non-neutral trunk postures can have adverse long-term

health effects on the lower back.

Bottoms and Barber (1978) evaluated a tractor seat with a

swivel of up to 20 degrees from the normal forward facing

position. The results of this study showed a decrease in

muscle activity in the shoulder and neck regions when the

seat was swiveled up to 20 degrees. Measured angles of the

body twist showed that the full potential benefit of the

swiveling seat was not used by the subjects, although the

mean twist between the shoulders and hips was reduced

significantly with increased swivel angle. This study confirmed that a swiveling seat was of benefit to the tractor

driver specifically performing tasks that required rearward

visual monitoring.

In a more recent study, Tore ́n and O ̈ berg (2001) investigated whether the exposure to twisted trunk posture was

affected when driving an agricultural tractor in the field

using freely swiveling saddle chairs. Ten subjects employed

as tractor drivers volunteered for this study. The results of

this study showed that the exposure to extreme twisted trunk

posture was slightly reduced during harrowing using the

saddle chair than the conventional chair. But for plowing,

the exposure to extreme twisted postures was reduced by

about 50% in comparison to the conventional chair. Thus, it

can be concluded that the use of a freely swiveling mechanism and enough space to swivel would be beneficial in

reducing postural stress.

Courtney and Chan (1999) performed an ergonomic

study to evaluate the workplace and workspace design of a

cab of grab unloaders for bulk material in ships. Their

results demonstrated that the drivers adopted poor postures,

partially due to the basic geometry of the situation and in

part due to using only the central lower front window for

downward vision and control boxes that obstructed operator’s vision. All of the drivers complained that they had to

maintain and perform their work in an awkward posture.

The main body parts that were problematic included the

neck (81%), the lower back (88%), mid-back (50%), and

shoulders (50%). About 56% of the drivers indicated that

they sought medical advice for these problems. It was

found that the operators spent 50% of the cycle time

looking vertically down. This resulted in static loading

of the neck and back with the trunk flexed forward 30 to

40 degrees and the neck flexed forward about 60 to 70

degrees from vertical to ensure proper viewing of the work

vertically below the cab. Similar results were found in a

previous study by Courtney and Evans (1993), albeit they

evaluated much older cabs than this study. Thus both of

these studies concluded that static loading of the trunk and

neck contributed to the various aches and pains experienced by the drivers. The authors of these studies made

recommendations for improving cab design to address

these concerns.

Gustafson-So ̈derman (1987) evaluated the effect of a seat

with an adjustable sitting angle and perceived discomfort in

the back, neck, and shoulder regions among crane operators. The crane operators had previously indicated that

discomfort was mainly contributed by a forward flexed

sitting position that happened during lifts close to the crane.

The seat with adjustable sitting angle (test seat) was

installed in one of the three cranes that were evaluated,

while the other two had an ordinary type of seat. The

highest estimated discomfort values were obtained from

operators using the ordinary seat and the lowest discomfort

values were obtained from the use of test seat with

adjustable sitting angle.

Sjøflot (1980) evaluated the use of big mirrors to

improve tractor driver’s posture and quality of work. Big

rearview mirrors make it possible for the driver to adopt a

good working posture. By using the big mirrors, the

operator’s time spent in twisted posture was reduced from

48% to less than 4% of the driving time when operating a

forage harvester. The hip-shoulder and neck angles were

considerably less awkward with the use of big mirrors than

without mirrors. There was no change in the chair-hip angle

with or without the use of big mirrors. When plowing, the

operator’s time spent in a twisted posture was reduced from

40% to 3.5% of the total driving time. In another study by

Nielsen (1986), the use of big mirrors was beneficial in

reducing the time required to view rearward work from

35% to 6% while driving the precision chopper and beet

harvester.

In summary, awkward postures during the operation of

heavy construction equipment are a consequence of improper cab design and work procedures. Poor visibility of the

task, limited room in the cab, excessive forces required to

operate levers/pedals, and improper seat designs are some of

the characteristics of a poorly designed cab. If not controlled, awkward posture of any body part can result in

increased risk of fatigue, pain, or injury. Exposure to

awkward postures either repetitively or for prolonged periods can lead to a variety of musculoskeletal disorders. Thus,

cab evaluations and improvements in cab design are necessary for reducing the adverse health effects experienced by

these operators (Kittusamy, 2003). Several of the studies

that were reviewed evaluated and discussed controls for

awkward posture. These studies have demonstrated that

postural requirements of work can be minimized with the

use of big mirrors, swivel seats, and seats with an adjustable
260 N.K. Kittusamy, B. Buchholz / Journal of Safety Research 35 (2004) 255–261

sitting angle. These and other controls can be incorporated

in the cab design to reduce exposure to awkward posture

when operating construction equipment.

4. Summary

Previous studies have indicated that operators of heavy

construction equipment (or other related equipment) are

afflicted by musculoskeletal injuries of the arms, shoulders,

neck, and lower back. From this review, it is shown that

WBV and the postural requirements of work (both static and

awkward postures) are important risk factors that contribute

to the development of musculoskeletal disorders among

OEs. In spite of this, very little research has been performed

that systematically characterizes the exposure of operating

engineers to these ergonomic hazards. The quantification of

vibration and postural requirements in practical settings is

necessary for developing a better comprehension of the

exposure levels that are present in different construction

equipment performing various tasks.

Acknowledgements

This work was performed when the corresponding author

was at the University of Massachusetts Lowell as a Research

Assistant on the Construction Occupational Health Project.

This project was funded by the National Institute for

Occupational Safety and Health (NIOSH) through the

Center to Protect Workers’ Rights (CPWR) (Grant # U02/

CCU312014). The authors would like to thank Drs. David

Wegman and Michael Ellenbecker for providing helpful

comments on earlier drafts. The authors also thank Emmett

Russell (from the International Union of Operating Engineers) and Danny Thiemens (from the Associated General

Contractors of America) for their valuable comments.

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