DOT/FAA/AM-99/17

Office ofAviation Medicine

Washington, D.C. 20591

The Influence of Ergonomie

Interventions on Employee

Stress and Physical Symptoms

Kurt M. Joseph

Richard C. Thompson

Larry L. Bailey

Clara A. Williams

Jody A. Worley

David J. Schroeder

Civil Aeromedical Institute

Federal Aviation Administration

Oklahoma City, Oklahoma 73125

June 1999

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, Virginia 22161.

©

U.S. Department

of Transportation

Federal Aviation

Administration

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19990629 079
NOTICE

This document is disseminated under the sponsorship of

the U.S. Department of Transportation in the interest of

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Technical Report Documentation Page

1. Report No.

DOT/FAA/AM-99/17

2. Government Accession No. 3. Recipienfs Catalog No.

4. Title and Subtitle

The Influence ofErgonomie Interventions on Employee Stress and Physical

Symptoms

5. Report Date

June 1999

6. Performing Organization Code

7. Authort»

Joseph, K.M., Thompson R.C., Bailey, L.L., Williams, CA., Worley, J.A.,

and Schroeder, DJ.

8. Performing Organization Report No.

9. Performing Organization Name and Address

FAA Civil Aeromedical Institute

P.O. Box 25082

Oklahoma City, OK 73125

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

12. Sponsoring Agency name and Address

Office ofAviation Medicine

Federal Aviation Administration

800 Independence Ave., S.W.

Washington, DC 20591

13. Type of Report and Period Covered

14. Sponsoring Agency Code

15. Supplemental Notes

16. Abstract

A recent report by the GAO (1997) indicates that private-sector employers spend as much as $20 billion annually for

employee injuries and illnesses due to musculoskeletal disorders (MSDs). While the etiologic mechanisms are poorly

understood, there is increasing evidence that psychosocial risk factors related to the job and work environment play a

role in the development ofwork-related MSDs. A longitudinal study was completed to determine the influence ofsix

psychosocial factors and two cost-effective ergonomics interventions on physical discomfort and stress scores reported by

employees within a Federal Aviation Administration organization. The results ofthe study revealed that stress scores

decreased significantly across time. However, physical symptom scores did not change across time, nor were they

affected by the ergonomic interventions. Two psychosocial factors provided significant and reliable adjustments to stress

and physical discomfort scores.

17. Keywords

Ergonomics Interventions, Psychosocial Risk Factors,

Stress, Physical Symptoms

18. Distribution Statement

Document is available to the public through the

National Technical Information Service,

Springfield, Virginia 22161

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

9

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
THE INFLUENCE OF ERGONOMIC INTERVENTIONS ON EMPLOYEE

STRESS AND PHYSICAL SYMPTOMS

BACKGROUND

A recent report by the United States General

Accounting Office (1997) indicates that privatesector employers spend as much as $20 billion annually for employee injuries and illnesses due to

musculoskeletal disorders (MSDs). While the etiologic mechanisms are poorly understood, there is

increasing evidence that psychosocial factors related

to the job and work environment play a role in the

development ofwork-related MSDs, particularly those

ofthe upper extremity and back (National Institute

for Occupational Safety and Health, 1997). Consequently, psychosocial factors, such as perceptions of

intensified workload, monotonous work, limited job

control, low job clarity, lack ofjob satisfaction, and

lack ofsocial support, may represent generalized risk

factors for work-related MSDs. The objective ofthe

present research was to explore the influence ofthese

factors on employee ratings of physical discomfort

and stress, and to determine if cost-effective ergonomic interventions would affect these ratings.

The research presented here is part of a longitudinal study designed to track and manage organizational changes related to the implementation of the

Electronic Document Management System (EDMS)

at the Federal Aviation Administration's (FAA's)

Civil Aviation Registry (hereafter referred to as the

Registry), which is located in Oklahoma City with a

staff of 250 employees. The types of jobs at the

Registry range from cashiers, who process application fees, to legal instrument examiners, who examine aircraft and airmen application packets to ensure

compliance with federal regulations. The Registry's

conversion from a manual documentsystem to EDMS

in the near future represents a significant organizational change, primarily because employees will be

required to learn and master new tools and procedures for completing daily functions and tasks. EDMS

will control workflow and the distribution of information with sophisticated software that employees

will manipulate usingvideo display terminals (VDTs)

and input devices (e.g., keyboard, mouse, etc.). Consequently, when EDMS becomes operational, exposure to VDT work is expected to increase over current

exposure rates.

Previous research has demonstrated thatincreased

exposure to VDT work is associated with increased

risk ofMSDs and elevated levels of physical discomfort, as reported subjectively by employees (Bergqvist,

1995). Furthermore, research assessing psychosocial

factors indicates that these factors can contribute

individually or in combination to influence both the

likelihood of reporting physical discomfort and the

perceived level ofthat discomfort (Bongers, De Winter, Kompier, Hildebrandt, 1993). The currentstudy

examined employee ratings of physical discomfort

and stress, and psychosocial factors across a 21-

month period to determine if these ratings were

influenced by two relatively low-cost ergonomic interventions. All employees received one ofthe interventions; approximately 60% received both.

Employees who received both interventions were

expected to rate stress and physical discomfort lower

than those receiving only one intervention. Although

the exact nature oftheir effect was uncertain, psychosocial factors such as subjective workload, monotonous work, job control, job clarity, job satisfaction,

and social support also were expected to uniquely

influence stress and physical discomfort scores.

METHOD

Two low-cost ergonomic interventions were developed to forestall anticipated increases in MSDrelated illness or injury due to increased exposure

rates to VDT work. All employees were included in

the first intervention, a 7-hr seminar in July 1997-

The seminar was comprised of an introduction to

MSD symptoms, an overview of psychosocial risk

factors associated with MSDs, ergonomic interventions for the office, and strategies for coping with

work-related stress. The second intervention included
145 employees, whose exposure to VDT work was

expected to increase with EDMS implementation.

Each of these employees received a workstation

"checkup" between the period of November 1997

and February 1998. The checkup was designed to

assess and adjust the current configuration ofworkstations so they conformed to a general set of guidelines that were based on the ergonomics research

literature. Each checkup consisted of a visit to an

employee's workstation, where an 18-item checklist

was used to reveal workstation problems associated

with MSDs. During the checkup, employees also

participated in demonstrations ofbasic software functions, including how to increase both text and toolbar

size, and work with multiple documents. Copies of a

"computer fitness brochure" (Great Performance,

Inc., 1993) were distributed to all employees who

received a checkup. Although every employee was

given this brochure at the one-day seminar, 53% of

those receiving a checkup recognized the brochure six

months later.

Two treatment groups were created based on type

of intervention. The "seminar" group received the

one-day seminar as an intervention, whereas the

"seminar + checkup" group received both the seminar

and checkup. The seminar intervention occurred

approximately one month after the first administration (May 1997) ofthe longitudinal survey. Approximately two-thirds of the seminar +. checkup

intervention had been completed at the time of the

second survey administration (December 1997). A

third administration ofthe survey was completed 14

months later, in February 1999. Each survey administration included a modified version of the Nordic

Musculoskeletal Questionnaire (Dickinson, Campion, Foster, Newman, O'Rourke & Thomas, 1992),

an internally developed 6-item overalljob stress scale,

and scales that measured the following psychosocial

factors: subjective workload (Hart & Straveland,

1988), job control (adapted from Festinger, 1957),

and satisfaction, social support, job clarity, and monotonous work (Camman, Fichman, Jenkins, and

Klesh, 1983).

Employees used a scale of 1 (not at all) to 5 (to a

very great extent) to rate physical discomfort for 12

different body areas, and they rated stress on a scale

of 1 (strongly disagree) to 7 (strongly agree). Factor

analyses were used to combine the 12 physical discomfort ratings into three unique dimensions, and

mean scores were calculated for these dimensions and

the stress ratings. Employees also used a scale of 1 to

5 to rate the extent to which they had ever experienced physical discomfort. This rating established a

baseline against which all other physical discomfort

scores could be assessed. Finally, a scale of 1 to 7 was

used to rate 5 psychosocial factors, the sixth factor,

subjective workload was assessed with a 1 to 21 scale.

A mean score was computed for the baseline physical

discomfort scale ratings and for each ofthe 6 psychosocial scale ratings. A 2 x 3 mixed design was used to

examine the effect of the ergonomic interventions

(i.e., seminar and seminar + checkup) across time

(i.e., May '97, Dec '97 and Feb '99) for each of the

outcome measures (i.e., 3 physical discomfort dimension mean scores and a stress mean score). Time

was treated as a within-subject variable, and the type

of ergonomic intervention served as a between-subject variable. Mean scores of ratings for the baseline

physical discomfort and 6 psychosocial factors (viz.,

subjective workload, monotonous work, job control,

job clarity, job satisfaction, and social support) were

treated as covariates within the design.

RESULTS

Factor analyses ofthe physical discomfort ratings

produced three unique dimensions that were reliable

across the first, second, and third survey administrations, and explained 68%, 68%, and 67% of the

variance ofthe 12 individual ratings included in the

respective analyses. The first dimension was labeled

Upper Torso and included ratings ofthe neck, shoulders, and upper and lower back. The second dimension was labeled Upper Extremity and consisted of

ratings ofthe elbows, wrists, and hands. Finally, the

third dimension was labeled Lower Extremity and

included ratings ofthe hips, thighs, buttocks, knees,

ankles, and feet.

ANCOVA was used to examine the temporal effects of the ergonomic interventions on scores for

stress and the Upper Torso, Upper Extremity, and

Lower Extremity dimensions. Figure 1 illustrates the

results of the ANCOVA for stress scores, which are

shown as a function of time and type of ergonomic

intervention. TheANCOVAyielded significant main

effects for time and type of ergonomic intervention.

Although the former main effect revealed that stress

scores generally decreased across time, the significant

decrement was confined to the period between Dec

'97 [M=4.4, SD=0.14] and Feb '99 [M=4.2, SD=0.15;
F(2,186)=3.01, p<.05, r|2

=.031]. The main effect for

type of intervention indicated that employees who

participated in the seminar 4iad signiftcarittyslower -

stress scores [M=4.0, SD=0.20] than employees who

participated in the seminar and received a workstation checkup [M=4.6, SD=0.12; F(l,93)=6.8, p<.02,

T|2=.068]. Table 1 shows correlations among covariates

and stress scores for May '97, Dec '97, and Feb '99.

All covariates were significantly correlated with stress

scores. However, only the baseline physical discomfort [F(l,93)=5.4, p<.03, T|2

=.055] and subjective

workloadscores [F(l,93)=29.3, p<.01, if=.239] uniquely

adjusted the stress scores.

Figures 2a, 2b, and 2c depict the results of the

separate ANCOVAs for Upper Torso, Upper JExtremity, and Lower Extremity physical discomfort

scores, respectively. These ANCOVAs revealed no

significant main effects for type of ergonomic intervention or time, nor did the analyses indicate a

significant interaction between these two variables.

Correlations among covariates and Upper Torso,

Upper Extremity, and Lower Extremity physical discomfort scores are displayed in Table 1. Several

covariates uniquely adjusted physical discomfort

scores in each ofthe three ANCOVAs. Although job

Intervention Type

Seminar + Checkup

* Seminar

Dec'97

Time

Feb '99

Figure 1. Mean stress scores as a function of time and

type of intervention.

Table 1. Correlations among covariates and stress scores, and Upper Torso, Upper Extremity and Lower Extremity

physical symptom scores.

Subjective

Workload

Monotonous

Work Job Control Job Clarity Job

Satisfaction

Stress (May'97)

Stress (Dec '97)

Stress (Feb '99)

UT(May'97)

UT(Dec'97)

UT(Feb'99)

UE(May'97)

UE(Dec'97)

UE(Feb'99)

LE(May'97)

LE (Dec '97)

LE(Feb'99)

Subjective Workload

Monotonous Work

Job Control

Job Clarity

Job Satisfaction

Social Support

'Correlation is significant at the 0.05 level (two-tailed).

** Correlation is significant at the 0.01 level (two-tailed).

Social

Support Baseline PS

**.550 ".354 "-.303 *-.172 "-.269 "-.273 ".487

".500 ".262 "-.280 -.142 •-.221 "-.261 ".308

".568 ".264 "-.279 *-.200 "-.299 "-.303 ".472

".409 .121 "-.231 *-.139 -.136 *-.172 ".776

".354 .031 -.150 *-.216 -.038 -.128 ".624

".410 -.052 -.059 "-.251 \175 \214 ".549

".382 .136 -.050 *-.154 -.059 -.081 ".692

".289 -.047 .045 *-.223 -.120 -.043 ".583

".292 -.071 "-.184 *-.219 -.083 -.098 ".482

".288 .102 "-.184 -.118 -.088 -.133 ".596

.144 -.035 -.106 -.121 -.001 -.066 ".455

.074 -.164 .092 *-.172 -.095 -.024 ".327

".371 M68 -.096 M63 "-.274 *.399

.059 ".284 ".228 .054 .110

".291 ".394

".352

".342

".310

".476

"-.233

"-.198

M75

\153
Figure 2a. Mean Upper Torso physical

discomfort scores as a function oftime

and type ofintervention.

0-

IIntervention Type

Seminar + Checkup

* Seminar

FebOT

Figure 2b. Mean Upper Extremity

physical discomfort score as a function

of time and type of intervention.

Intervention Type

Seminar + Checkup

Seminar

FebW

Figure 2c. Mean Lower Extremity

physical discomfort score as a function

of time and type of intervention.

May 97

Intervention Type

Seminar + Checkup

Seminar

Feb^
clarity and Upper Torso physical discomfort scores

were significantly correlated, only baseline physical

discomfort [F(l,91)=74.6, p<.01, T|2=.450] and subjective workload scores [F(l,91)=10.8, p<.01, r\2

=.106] uniquely adjusted Upper Torso physical discomfort scores. Job clarity scores also correlated

significantly with Upper Extremity physical discomfort scores. However, only baseline physical discomfort [F(l,90)=59.0, p<.01, r|2

=.396], subjective

workload [F(l,90)=3.7, p<-05, rf =.039], and job

control scores [F(l,90)=5.6, p<.02, r|2=.059] provided unique adjustments to Upper Extremity physical discomfort scores. The Lower Extremity physical

discomfort scores were uniquely adjusted by baseline

physical discomfortscores only [F( 1,92)=45.9, p<.01,

TI2=.333].

DISCUSSION

The pattern of results for employee stress scores

indicated that stress decreased across time. The reduction in stress became more pronounced during

the period between Dec '97 and Feb '99, and was not

a consequence of either of the ergonomic interventions. Although stress scores were significantly higher

for employees who received the seminar + checkup

relative to those who attended only the seminar, the

former group of employees reported significantly

higher stress scores throughoutthe study period. The

absence ofa significantinteraction between intervention type and time indicates that the difference in

stress scores remained constant over time. Overall,

the level ofstress experienced by employees appears

to be equivalent to that found in other work settings

(e.g., see Paulsen, 1994).

Even though Upper Torso, Upper Extremity, and

Lower Extremity physical discomfortscores decreased

slightly over time, this change was not significant.

Nor was there a significant change in discomfort

scores as a result ofthe two ergonomic interventions.

Overall, Figures 2a, 2b, and 2c illustrate that employees reported minimal discomfort throughout the

study period. In fact, any effects attributable to the

ergonomic interventions may have been undetectable

because physical discomfort scores, especially those

for the Lower and Upper Extremity dimensions, were

near the lowest scale value (i.e., 1.0) throughout the

study period. Interestingly, physical discomfortscores

did not increase as a consequence of employees becoming more aware of the causes, symptoms, and

psychosocial risk factors associated with MSDs. Previous research on this matter is equivocal and employers' reluctance to initiate ergonomics programs is

based partly on concerns aboutincreases in reports of

physical discomfort, MSDs, and worker compensation costs (Melhorn, 1999).

The baseline physical discomfort scores provided

significant and reliable adjustments to stress and the

three physical discomfort dimension scores. The correlation coefficients in Table 1 illustrate that the

significant relationship between the former and latter

scores was moderately positive. This finding is consistentwith earlier research and suggests that employees should be screened upon entry into a workforce so

that employers have a baseline measure of physical

symptoms against which comparisons can be made

when important changes occur within an organization. Another covariate, subjective workload, also

significantly adjusted employees' stress and physical

discomfort scores, with the exception ofthose for the

Lower Extremity dimension. As with prior research

examining VDT users (e.g., Sauter et al., 1983), and

as can be seen in Table 1, the association between

subjective workload and the outcome measures was

moderately positive and significant. The effect sizes

(i.e., r|2) of the baseline physical discomfort and

subjective workload covariates were consistently

higher than any of the other effects observed in this

research. Hence, subsequent research using employee

reports of physical discomfort and stress as outcome

measures must not overlook the unique adjustment

that these covariates provide to outcome measures.

The longitudinal research reported here provides

important baseline information that will be used to

assess changes that result from EDMS implementation at the Registry. The research will continue to

track employee reports of physical discomfort and

stress, along with other data, in an effort to provide

trend information that will more fully and reliably

assess the effects ofthe ergonomics interventions and

psychosocial factors.
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