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Short-Term Effects of Workstation Exercises on Musculoskeletal Discomfort and Postural Changes in Seated Video Display Unit Workers

A Fenety, PT, PhD, is Assistant Professor and Undergraduate Coordinator, School of Physiotherapy, Dalhousie University, Forrest Bldg, 5869 University Ave, Halifax, Nova Scotia, Canada B3H 3J5 (anne.fenety{at}dal.ca).
JM Walker, PT, PhD, is Professor (Retired), School of Physiotherapy, Dalhousie University

Address all correspondence to Dr Fenety

Submitted January 9, 2001; Accepted January 5, 2002

	Abstract

 
Background and Purpose. In recent years, a number of exercise programs have been developed for computer operators in order to promote movement and to reduce musculoskeletal discomfort. Tests of the effectiveness of these exercise programs, especially in field trials, are rare. The authors tested the hypothesis that doing regular, short-term (<10 days) exercises while at a workstation would decrease musculoskeletal discomfort and increase in-chair movement (ICM). Subjects. Eleven directory assistance operators (8 female, 3 male) with no recent history of musculoskeletal problems volunteered. Methods. In-chair movement was measured by tracking the center of pressure at the buttock-chair interface as subjects sat on a pressure-sensitive mat. Musculoskeletal discomfort was rated through the use of the Body Part Discomfort Scale (BPDS) and a body map. We used a revised Dataspan exercise program. Operators were tested for 2 hours, on 2 occasions: before and after doing exercises for 3- to 5-day shifts. During each test, ICM was measured during three 15-minute periods at the start of the test and at the end of hours 1 and 2. Subjects rated musculoskeletal discomfort per body part using the BPDS at 30, 60, and 120 minutes of each test. The effects of exercises on ICM and BPDS ratings were examined with a two-way repeated-measures analysis of variance with day (2) x time (3) designs. Results. When subjects were doing their exercises, ICM was higher at the start and hour 1, and perceived discomfort was lower during each test period (start, hour 1, and hour 2). When not exercising, subjects' musculoskeletal discomfort increased over time and was higher during all test periods. Discussion and Conclusion. Exercises done by video display unit operators while at a workstation resulted in short-term decreases in both musculoskeletal discomfort and postural immobility. These results suggest that workstation exercises may be beneficial.

Key Words: Sitting discomfort • Stretching • Video display unit • Workstation exercises

	Introduction

Top Abstract Introduction Workstation Exercises:... Evaluation of Workstation... Method Results Discussion Conclusion Appendix References

 
Two thirds of the North American workforce sit for all or part of their day, and most work with video display units (VDUs).¹ Extended work with VDUs is associated with 2 factors predictive of musculoskeletal problems: infrequent postural changes² and the presence of discomfort while sitting.³ Posture, postural changes, and discomfort while sitting are all, in our opinion, interrelated. According to Teiger,⁴ any sitting position achieved by VDU operators represents the resolution of ongoing conflicts between internal constraints (eg, need for comfort), external constraints (eg, worker/workstation fit), the task (eg, need for precision), and work organization factors (eg, performance expectations). Those same constraints and needs also dictate the frequency of postural changes in seated workers.^4,5 We refer to these changes as "in-chair movements" (ICMs). Sometimes the resolution of the conflict favors limited ICM, and sometimes it favors frequent ICM.^6,7

Infrequent ICMs have long been considered to be a primary risk factor in the development of work-related musculoskeletal disorders (WRMDs).⁸ Frequent ICMs have long been considered to be related to sitting discomfort.^6,7 Presumably, there is some balance between those 2 ends of the spectrum, with a pattern of ICM that does not lead to discomfort or risk of injury. Little evidence, however, exists.^7,9 A growing body of literature^6,7,10 has shown that, when first seated, working subjects are comfortable and move little. Their discomfort, however, increases over time and appears to lead to increases in ICM.^6,7,10 One challenge for researchers would be to determine whether promoting ICM when a VDU operator sits would limit the discomfort over time, thereby reducing the risk of musculoskeletal problems.^2,3

Work with VDUs has changed from simple data-entry tasks to interactive task. For example, one rapidly expanding area of VDU work is sales and service via interactive, electronic means (ie, telephone and Internet connections). Sales and service work, typically conducted in call centers, is characterized by external workload pacing in which the pace of incoming calls is controlled by a computer, not by the operator.¹¹ External pacing conditions limit a VDU operator's ability to take self-selected breaks away from his or her workstation,¹² especially breaks to exercise.¹³ Several exercise programs have been introduced for VDU operators.^14–20 These exercise programs are designed to reduce musculoskeletal discomfort and increase ICM in VDU operators. Instruction for these exercises is now available in electronic format (www.tifaq.org/software.html), but only a few exercise programs have been field tested for their effectiveness in reducing discomfort.^14–17 None have been examined with VDU operators who work under paced workload conditions. The claim that workstation exercises increase ICM also has not been substantiated. Finally, despite the difficulties encountered in returning patients with musculoskeletal problems to seated work, no literature was located regarding workstation exercises. These issues are addressed in our study.

	Workstation Exercises: Interventions and Critique

Top Abstract Introduction Workstation Exercises:... Evaluation of Workstation... Method Results Discussion Conclusion Appendix References

 
Research on the effects of workstation exercises for seated VDU operators has led to variable results.^14–20 Saltzman¹⁷ showed reduced muscle stiffness and discomfort in VDU operators who took frequent short stretching breaks. Our review of the literature^* (Tab. 1) shows quite another result. Most researchers reported that workstation exercises appear to be ineffective in reducing musculoskeletal discomfort. Each of these studies, however, has what we would consider limitations. Most ergonomists consider that there are 2 fundamental study design elements needed to measure discomfort.^7,9,21 There should be comparison of preintervention and postintervention discomfort, as well as measurement of discomfort over time.²⁰ In no cases were both components evaluated in the exercise studies we reviewed. The exercise programs may have failed to reduce discomfort because, with one exception,¹⁶ they were developed by specialists (eg, exercise physiologists, physical therapists) based on the perceived demands of the VDU operators' tasks, rather than on specific health problems identified by the VDU operators (eg, musculoskeletal discomfort). In addition, adherence to exercise programs was taken into account only in the 3 most recent studies.^15–17 Consequently, not all exercise (or rest) breaks may have been taken. We question whether poor adherence may have diminished the effect of the exercises in these intervention studies. In-chair movement was not considered in any study that we reviewed.

	Evaluation of Workstation Exercises

Top Abstract Introduction Workstation Exercises:... Evaluation of Workstation... Method Results Discussion Conclusion Appendix References

The first purpose of our study was to test the hypothesis that electronically paced directory assistance operators doing regular workstation exercises on a short-term basis (ie, 3- to 5-day shifts spread over 5–10 days) would, over the 2 hour test period: (1) increase their ICM, (2) not experience increases in musculoskeletal discomfort over time, and (3) have decreased whole-body musculoskeletal discomfort. The second purpose of our study, in order to assist our interpretation of the results, was to evaluate subjects' responses to the revised exercise program via an exercise satisfaction questionnaire.

	Method

Top Abstract Introduction Workstation Exercises:... Evaluation of Workstation... Method Results Discussion Conclusion Appendix References

 
Subjects

Eleven people (3 male, 8 female) who had been employed as directory assistance operators for an average of 78 months (SE=18.6, range=20.5–190) participated on a volunteer basis. The subjects ranged in age from 22 to 41 years (=29.5, SE=1.9). Their mean height was 172.9 cm (SE=2.1, range=162.5–185.4), and and mean weight was 69.6 kg (SE=3.9, range=49–84.4). All directory assistance operators in the company were notified of the study by use of posters and letters. The study was open to part-time and full-time operators and to men and women. All subjects had to have at least 3 months of experience in directory assistance operations. Subjects were excluded if, at any time during the 3 months leading up to the study, they experienced any musculoskeletal problems that required the intervention of a health care practitioner²⁵ or general health problems, such as hemorrhoids, that affected sitting comfort. Subjects wearing corrective eyewear were accepted into the study on the provision that their eyewear did not change during trials. For those participants who met the preceding criteria, only those directory assistance operators scheduled to work 5- to 7-day shifts during specified 10-day periods were accepted into the study. All volunteers who met all the preceding inclusion and exclusion criteria were accepted into the study.

Using statistical results from previous subjects (N=8),¹⁰ we calculated that a sample size of 15 was needed to achieve a power of .95. This was not achieved because of insufficient time prior to major restructuring that took place in the Canadian telecommunications industry. These same changes precluded the planned long-term (6-week) follow-up phase of the study. Prior to recruiting subjects, the employer and representatives from the directory assistance operators' union signed a participation agreement. Prior to participating in the study, subjects gave their signed informed consent. The research was approved by the Human Ethics Review Committee of Dalhousie University's Faculty of Graduate Studies using Research With Captive Populations guidelines from the Medical Research Council of Canada (now the Canadian Institute of Health Research).

Task Description

The VDU task used in this study (ie, directory assistance at a local telephone company) was chosen because the task, workload, environment, and furniture were standardized.¹⁰ The operators' tasks were centered on a VDU and a headset and required no movements other than use of a keyboard, screen viewing, and speaking to customers via a headset. The operators primarily responded to requests for directory assistance and, to a lesser extent, handled intercepts on disconnected or out-of-service numbers.

Equipment Used for Measurement of Perceived Discomfort

Perceived discomfort was rated using the Body Part Discomfort Scale (BPDS),²¹ a 6-point visual analog scale (0="no discomfort," 5="intolerable discomfort"). Discomfort was localized to body regions (eg, pelvis, shoulder) using the Localized Musculoskeletal Discomfort (LMD) body map.²⁶ The BPDS is based on the assumptions that discomfort is influenced by working posture, by the effort required to complete a task, and by the duration of the task. In their validation study, Corlett and Bishop²⁷ measured discomfort in spot welders (N=17) on multiple occasions over a 1-month period. Subjects worked under a range of conditions for posture (ie, suitable to unsuitable workstation height), foot pedal effort (ie, suitable to unsuitable force required), and time (up to 3 hours). Results showed that as work conditions varied (ie, suitable versus unsuitable) or as time passed, the level of discomfort varied. The results also showed that each level of discomfort had "a recognizable distribution about a mean value" (no statistics reported). For example, the combination of a workstation set too high, a foot pedal with high resistance, and working time greater than 2 hours results in an average BPDS rating in the "intolerable discomfort" range. Reliability of BPDS ratings of discomfort has not been reported.^7,21 In terms of the LMD body map, van der Grinten²⁶ showed that subjects (N=16) had the most reliable results for localizing uncomfortable body parts (Pearson r>.75, P<.05) when the LMD body map had only 19 body parts and individual body part ratings (eg, buttock) were combined to create regional scores (eg, buttock + thigh + knee + lower leg).

We analyzed whole-body scores for perceived discomfort (ie, the sum of the pelvis, buttock, back, neck, shoulder, and arm scores averaged over the number of uncomfortable body parts) obtained using the BPDS. Prior reliability studies,¹³ in which the intraclass correlation coefficient (ICC [2,1])²⁸ was used, showed that whole-body scores were more reliable (ICC [2,1]>.90) than individual body part scores (eg, ICC_pelvis=.63, ICC_neck=.67) for measuring perceived discomfort.

Equipment Used for Measurement of In-Chair Movement

In-chair movement was measured by tracking center-of-pressure (COP) changes at the buttock-chair interface as subjects sat on a VERG (Vision Engineering Research Group) pressure-sensing mat. The VERG mat is a 15 x 15 array of force-sensing resistors embedded in a 2-mm-thick rubber mat. Previous research showed that, as a result of the mat's thin profile, it readily conformed to chair seat contours and did not influence chair comfort.¹³ In a series of trials with 12 subjects, Al-Eisa et al²⁹ demonstrated intertrial reliability of data obtained with the VERG mat for detecting mean pressure peaks (ICC [2,1]=.83–.97).

Validation.
The COP is calculated by summing the pressure moments about the defined origin (0,0). Movement of the subject's COP is tracked in 2 planes simultaneously: forward and backward and left and right. We operationally defined in-chair movement as any movement of the chair occupant that changes the position of the COP. We based our operational definition on the following 3 assumptions about ICM and COP: that the seat supported most of the subject's body weight, that the predominant form of loading was compression, and that the acceleration components of seated postures were minimal.¹⁰

Data collection and reliability.
Online data were collected continuously and stored in 24 five-minute blocks. Post-collection software was used to calculate the total COP distance traveled in the 2 horizontal dimensions for each block. Our ICM data analysis protocol was based on the results of a previous reliability study conducted on the job with 8 directory assistance operators.¹⁰ We chose to collect ICM data as the means of 3 consecutive 5-minute blocks because the intertrial reliability of data obtained for 3 blocks (ICC [2,3]=.90–.96) was greater than the reliability of data obtained with any single 5-minute block (ICC [2,1]=.76–.89). Subjects were shown how the mat is used to collect interface pressure data, but they were masked to the fact that ICM would be derived from the interface pressure data by tracking the COP. Greater detail regarding the methods has been reported elsewhere.¹⁰

Dataspan exercises.
A Dataspan Ergonomic Skills Training Program³⁰ was purchased by the telephone company 4 years prior to our study. The Appendix contains details of how we revised and implemented this program. At the end of the study, subjects were given an exercise satisfaction questionnaire about the revised Dataspan program. The questionnaire was based on the exercise critique guidelines described by Lee et al.³¹ The questionnaire was completed and returned by mail. Subjects were asked to: (1) comment on the ease or difficulty of performing the exercises, doing the exercises without disrupting work, remembering to do the exercises, and doing the exercises without feeling conspicuous, (2) comment on the number and variety of exercises, (3) identify any problems encountered with particular exercises, and (4) provide general comments and suggestions.

Test Procedure

Subjects were tested twice, with each test session lasting 2 hours. Test sessions were conducted exclusively during day shifts, with each subject's first and second tests taking place at the same time of day. Because there was an influence of the time of day on discomfort,³² the design was counterbalanced with 6 subjects tested at the start of a morning shift and 5 subjects tested after lunch. Subjects were first tested before the exercises were begun. At the end of that test, the revised Dataspan program was shown to the subjects, including explanations as well as demonstrations and practice of the exercise and relaxation techniques. The second test took place after the operators had worked from 3- to 5-day shifts, during which they were expected to take one workstation exercise break every 30 minutes.

For the exercises, subjects were instructed to stretch until they felt a comfortable sensation of muscle tension and then to hold that position for 5 seconds. The 5-second hold, although shorter than some current recommendations for holding a position during stretching (ie, 15–30 seconds),³³ was a compromise. The 5-second hold was based on the operator's allowable time for an exercise break (ie, number of exercises x number of repetitions x 5-second hold). Because exercise break time meant lost productivity (ie, time away from taking calls), the exercise break time was negotiated among, and agreed upon, by management, union representatives, and the researchers. Subjects were inconspicuously observed for adherence to the exercise program during the actual exercise tests and at least once between the first and second test sessions. This was done in a manner designed to make the observer inconspicuous. One researcher (AF) was available on site to provide follow-up as requested by the subjects regarding workstation exercises in general. Subjects' total duration in the program ranged from 6 to 10 days.

The test protocol for both ICM and perceived discomfort data collection is illustrated in Figure 1. Subjects provided perceived discomfort ratings at the 30-, 65-, and 115-minute marks. For each perceived discomfort rating, subjects were asked to close their eyes and evaluate discomfort by briefly focusing on each body part being characterized in turn. In order to evaluate ICM trends that coincided with ratings of perceived discomfort, ICM data were analyzed as the mean of 3 blocks at the start of the test (minutes 5–20), at the end of hour 1 (minutes 50–65), and the end of hour 2 (minutes 100–115). Subjects signed off their computers to rate their perceived discomfort. During the exercise test, subjects were not told to take an exercise break. Henning et al¹⁵ suggested that encouragement to do workstation exercises is not enough to get subjects to do exercises. Therefore, subjects were cued visually (at 35, 65, and 90 minute) when 30 minutes had passed. These 30-minute cues were outside the time period when ICM data would be analyzed (Fig. 1).

View larger version (22K): [in this window] [in a new window] Figure 1. Field test protocol for in-chair movement (ICM). Data were collected continuously (0–120 min), but analyzed as three 15-minute blocks (start, end of hour 1, end of hour 2), and perceived discomfort ratings were collected during three 5-minute periods (30–35, 65–70, 115–120 minutes).

	Results

Top Abstract Introduction Workstation Exercises:... Evaluation of Workstation... Method Results Discussion Conclusion Appendix References

 
In-Chair Movement

Tests of simple (ie, interaction) effects of exercises revealed that movement was greater with exercises in the first period (5–20 minutes) and second period (50–65 minutes), by 68.7 cm (P=.02) and 44.2 cm (P=.03), respectively (Fig. 2). In the final 15 minutes, there as no difference between pre-exercise and exercise conditions. Testing of time alone showed that ICM increased by 86.8 cm (P<.01) over the 2-hour test period in the pre-exercise condition. However, because ICM was consistently high throughout the exercise test, ICM did not increase over time when exercises were used.

View larger version (11K): [in this window] [in a new window] Figure 2. In-chair movement (ICM) (measured via center-of-pressure [COP] distance) versus time (mean, SE): start (5–20 minutes), end of hour 1 (50–65 minutes), and end of hour 2 (100–115 minutes). Main effects and interaction effects were determined by repeated-measures analysis of variance (N=11). In the pre-exercise condition, ICM increased over time by 86.8 cm (F=15.5; df=20,2; P<.01). With exercises, the time effect was removed because ICM was high over the entire 2 hours. Compared with the pre-exercise condition, ICM was greater with exercises in the first (5–20 minutes) sample period (68.7 cm; F=8.63; df=10,1; P<.05) and the second (50–65 minutes) sample period (44.2 cm; F=6.75; df=10,1; P<.05). By the end of the 2 hours, there was no difference between the 2 conditions (F=0.01; df=10,1; P=.92).

View larger version (15K): [in this window] [in a new window] Figure 3. Average whole-body perceived discomfort versus time (mean, SE) at 30, 65, and 115 minutes. Main effects and interaction effects were determined by repeated-measures analysis of variance (N=11). In the pre-exercise condition, whole-body discomfort was greater at minute 30 (0.38 unit; F=11.81; df=10,1; P<.01), minute 65 (0.66 unit; F=10.11; df=10,1; P<.01), and minute 115 (0.93 unit; F=17.65; df=10,1; P<.01). Over time, whole-body discomfort increased in both conditions, but was significantly greater only in the pre-exercise condition (1.03 units; F=14.72; df=20,2; P<.05).

	Discussion

Top Abstract Introduction Workstation Exercises:... Evaluation of Workstation... Method Results Discussion Conclusion Appendix References

Effect of Exercises on In-Chair Movement

The results upheld the hypothesis that ICM would increase after short-term use of workstation exercises. Following short-term use of the workstation exercise program, operators showed increases in ICM during the first and second test periods. The increases in ICM may be attributable to the following rationale presented to the operators regarding the exercises. During introductory sessions, physiological problems related to poor postures and infrequent postural changes (eg, buttock pressure, decreased circulation) were discussed. The operators were told that to reduce those problems, they needed to move (ie, to perform workstation exercises). The increases also may be due to factors beyond our control, including job stressors not measured in this study (eg, external workload pacing). The effects of these external factors on ICM cannot be ruled out, because the design (pretest-posttest) did not include a return to baseline (ie, pretest) conditions, which would have allowed us to isolate the treatment effects. We acknowledge that the increase in movements may be due to the motion associated with exercises. We believe, however, that the effect would be minor because the 30-minute time cues were intentionally delayed until after the first and second periods of ICM data collection. Although subjects knew they could do the exercises at will, they rarely did them before the 30-minute cues.

The uniqueness of our ICM measures, in our view, presents a challenge for interpretation. For example, the 44.2-cm difference in ICM between pre-exercise and exercise conditions during an average 5-minute period at the end of hour 1 was real. Clinical relevance is more difficult to establish. To do so, we first turn to previous calibration results. Fenety¹³ showed that there was considerable variation in the amount of movement of seated subjects' COP during selected tasks and postural changes. Typical keyboard activities performed while taking telephone calls resulted in minimal COP movement (eg, <0.25 cm), whereas moving the trunk from upright to resting on the backrest resulted in a greater mean COP excursion of 2.5 cm (SD=0.5). Larger excursions occurred when subjects crossed (or uncrossed) their ankles (=5.5 cm, SD=1.2) or when they moved from sitting upright to slouching (=7.1 cm, SD=1.6).¹³

We believe the results of another study further clarify clinical relevance. Using a modified posture targeting techniques,¹² we randomly sampled the postures of 22 directory assistance operators in multiple 5-minute blocks over 5 working days. Fenety¹³ showed that the operators primarily worked in rigid (ie, fixed) positions with occasional major postural changes, such as slouching. These major shifts in posture often occurred when the "calls waiting" signal was not present (ie, there was less time pressure). Considering the results from our calibration and posture targeting studies, it is likely that several larger ICM excursions took place in order to get that 44.2-cm difference in the 3-block average.

Finally, we advise caution regarding the interpretation of the ICM increases under exercise conditions because it is not known why seated subjects move at all. Using simultaneous measures of ICM and discomfort, some authors^6,7 have suggested that the 2 variables were correlated. The best evidence linking discomfort with the need to move, however, comes from Zhang and Helander.³⁵ Subjects associated sitting discomfort with feelings of constraint (eg, stiffness, cramping, restlessness, poor circulation), which suggests that ICM may serve to reduce those problems and, as a result, promote comfort.³⁵

Effect of Exercises on Musculoskeletal Discomfort

Our hypotheses regarding musculoskeletal discomfort were supported by study findings. We found that short-term use of workstation exercises curbed the growth of discomfort over time. Like Swanson and Sauter,¹⁸ we found that discomfort increased temporally in both test conditions, but in our study the effect was not significant when subjects were using workstation exercises. Although the workstation exercises did not eliminate discomfort, their greatest effect was to minimize the rapid growth of discomfort in the second hour, as shown in Figure 3. The results supported our second hypothesis that whole-body discomfort would be reduced under exercise conditions. In the only other study that evaluated exercise and pre-exercise conditions in VDU operators, Henning et al¹⁴ found the only change after 3 weeks of exercises was a nonsignificant decrease in leg discomfort. Given the number of methodological differences between our study and that of Henning et al,¹⁴ we believe the 2 studies are not comparable.

Implications of Workstation Exercises on Reducing Musculoskeletal Discomfort

Because directory assistance operators report high rates of musculoskeletal discomfort in regions such as the back (80%–84%) and neck (67%–72%),^36,37 our key finding that discomfort can be reduced by workstation exercises is important. Workstation exercises did not eliminate discomfort. Based on previous results,^14,18 more breaks are not likely the answer, either.

Research involving controlled clinical trials in the area of WRMDs is limited. Kuorinka and Forcier³⁸ acknowledged that the precision with which a given cause (ie, a work-related factor) results in a negative outcome (eg, WRMD) is low. We acknowledge that the likelihood that our intervention (ie, workstation exercises) would result in an improved outcome (ie, fewer musculoskeletal problems) is similarly low. Despite that limitation, one of the most common first symptoms associated with WRMDs is discomfort,³⁸ and we have demonstrated one means to reduce discomfort. A variety of other options have been suggested to reduce discomfort, including job rotation,³⁹ increased task variety,⁹ and relaxation of muscles not involved directly in tasks.⁴⁰ Although it appears that the reduction of musculoskeletal discomfort will require a multifaceted, possibly expensive, approach, there will be benefits. Unfortunately, due to the short-term nature of our study, we cannot infer that reduced discomfort would result in cost savings or improved quality of worklife. There is, however, evidence that the introduction of stretching and rest breaks decreased the incidence of WRMDs over a 6-month period in 72 electronic-based sales and service representatives tracked over 30 months.⁴¹

General Considerations of Workstation Exercises

Method.
Because our short-term use of a revised Dataspan exercise program resulted in improved comfort and increased ICM, we examined reasons for the program's success. First, we considered the program's content (eg, small number of exercises, brochure format) and administration (ie, exercises reviewed) as possible reasons. These changes may have benefited some, but not all, subjects, because over half of the directory assistance operators had difficulty remembering or finding time to perform the exercises due to time pressure. We considered other reasons. For example, revisions to the exercise program were based on specific musculoskeletal complaints made by the directory assistance operators during interviews. In addition, the operators may have benefited not just from the exercises, but also from breaks due to exercise periods. Zwahlen et al⁴² have presented descriptive evidence that regular rest breaks are related to the temporal growth of musculoskeletal discomfort. In our study, the effects of taking a rest break, therefore, may be confounded with the effects of taking an exercise break. To date, no researcher has demonstrated any difference in perceived discomfort between rest breaks only and rest breaks plus exercises.^14,15,18

Adherence.
A common reason cited for the failure of long-term (>1 year) workplace exercise programs is that discomfort patterns are resistant to change.¹² We showed that changes occurred in less than a week. Long-term exercise programs, therefore, may fail for other reasons, such as nonadherence to the exercise program. Based on survey data, Silverstein et al¹² reported that a 1-year program to reduce discomfort in industrial workers was unsuccessful when two thirds of workers claimed participation that ranged from "some exercise" to "daily exercise." Participation (ie, adherence) can be monitored, but it generally requires human resources, such as team leaders.³⁰ Despite monitoring, the use of small groups, and the use of team leaders, the original Dataspan program at the telephone company where we conducted our study failed when introduced 4 years previously. Similarly, Silverstein et al¹² reported that, despite their subjects' reports of feeling better with exercises, their adherence to the exercise protocol declined. If, as it appears, exercise adherence requires repeated follow-ups and ongoing program modifications, the cost of workstation exercises may be high. Nonetheless, we believe those costs may be offset by the exercise benefits demonstrated in our study, namely the potential to decrease discomfort—a risk factor in the development of musculoskeletal problems.³ Ultimately, to determine their ergonomic value, a cost-benefit analysis of workstation exercises would be required, including measures of productivity and long-term health effects.

Conflict between exercises and job performance.
Answers to our questionnaire identified a potential problem that we contend is related more to ergonomics than to physical therapy. Seven of the 11 directory assistance operators reported difficulty in finding (or making) time to do the exercises. That is, although our results show that exercising reduced discomfort, the operators found it difficult to stop and do the exercises, particularly when they were under time pressure (eg, when calls were waiting). Those comments reinforce the contention of Henning et al¹⁵ that poor adherence to exercise programs is most often due to a conflict between exercise demands and task demands, particularly when work is paced. The directory assistance operators in our study worked under electronic pacing and electronic performance monitoring. We believe that because of the pacing conditions, long-term adherence to the revised Dataspan program would likely decline unless some organizational changes occur. One solution to alleviate the conflicting demands of job performance and exercise breaks may be to shift the responsibility for "making time" for a break from the operator to management. The telephone company could accomplish this by programming online exercise prompts or by signaling breaks with light-emitting diodes mounted on each computer.⁴³ The change in responsibility would decrease the risk of forgeting the exercises and would signal that the break was sanctioned by management. Whether this would be beneficial warrants additional research.

Specific exercise problems.
Minimal problems with the exercises were reported. Two operators (18%) reported wrist discomfort during wrist stretching. This figure is similar to the daily prevalence of wrist discomfort reported by telecommunication workers.³⁶ Considering that the extension-in-standing exercise was novel, the single complaint of discomfort with that exercise was lower than we expected. No problems were reported by subjects with respect to the duration of the muscle stretches. We used 5-second stretches to reduce the operators' time away from work and thereby encourage their adherence. Given the time constraints in directory assistance operations, the recommended 15- to 30-second holds for each muscle or muscle group stretched^33,44 would be unrealistic for workstation exercises. Therefore, in the future, we suggest that the short-duration workstation stretching exercises be continued by the directory assistance operators, but augmented with one daily set of prolonged (30-second hold) stretching exercises performed during "down" times (eg, not taking calls). We have no data, however, indicating this would be beneficial.

Study design.
Our previous ICM reliability study¹⁰ showed high between-subjects variability. This led us to not use a control group. Instead, we thought it appropriate to use a repeated-measures design. Accordingly, we took a number of precautions to limit any Hawthorne effect.⁴⁵ First, subjects were masked to the fact that ICM data were being derived from the VERG mat recordings. Second, the entire directory assistance operations staff was invited to participate in some aspect of this study. For example, the majority of the company's 145 directory assistance operators took part in the exercise review and revision process, and all were given the opportunity to learn the revised exercise protocol. In addition, no preferences were given to the study volunteers with respect to breaks, salary, or shift assignments. Finally, at the start of this study, all directory assistance operators would likely have accommodated to the researchers who, at that point, had been present in the directory assistance operations sector on a regular basis for 14 months. Although repeated-measures designs are susceptible to learning effects, previous results showed no between-trial differences in ICM or perceived discomfort during repeated baseline tests.¹³

Generalizability.
The results of this study cannot be generalized to long-term applications because adherence will likely vary across time. The sample size was small, and subjects were screened on the basis of musculoskeletal health. Subjects also represented only one occupational group, directory assistance operators, a group in which musculoskeletal discomfort rates exceed general rates.^36,37 The type of computer used by directory assistance operators also is different from that used by most VDU operators. Compared with data-entry clerks, directory assistance operators use fewer keystrokes per hour and are more likely to be electronically monitored and paced.³⁷ The directory assistance operators reported difficulties in finding time to perform exercises, a less likely scenario for unpaced VDU operators.¹² Although we believe these results are not generalizable to typical VDU users, we contend that they are applicable to a rapidly expanding sector of the workforce—a sector that includes 3% of Canadian workers.⁴⁶

	Conclusion

Top Abstract Introduction Workstation Exercises:... Evaluation of Workstation... Method Results Discussion Conclusion Appendix References

 
Based on our results, workstation exercises appear to be an appropriate tool in the prevention of discomfort and in the promotion of ICM. Given the rapid increase in office computerization and sitting-related problems, this is important. However, time constraints should be considered when prescribing workstation exercises for these electronically paced VDU operators.

	Appendix

Top Abstract Introduction Workstation Exercises:... Evaluation of Workstation... Method Results Discussion Conclusion Appendix References

 

View larger version (139K): [in this window] [in a new window] Appendix. Exercise Program Revision

	Footnotes

 
Both authors provided concept/research design and writing. Dr Fenety provided data collection and analysis, subjects, and project management. Dr Walker provided fund procurement, facilities/equipment, institutional liaisons, and consultation (including review of manuscript before submission).

This study was approved by the Human Ethics Review Committee of Dalhousie University's Faculty of Graduate Studies.

This study was funded, in part, by a Postgraduate Scholarship to Dr Fenety from the Natural Sciences and Engineering Research Council of Canada.

This study was presented, in part, at the 12th International Congress of the World Confederation for Physical Therapy; June 25-30, 1995; Washington, DC.

^* We conducted our review of the literature using the following databases: MEDLINE, CINAHL, NIOSHTIC, SPORT DISCUS, EI COMENDEX, Ergonomics Abstracts, and online using SavvySearch.com. We used the following key words in our literature search: exercises, physical therapy, posture, sitting, stretching, workplace, workstation, and VDU.

Sample size was calculated using the standard deviation and smallest detectable difference for the dependent variable with the greatest variability (ie, ICM).

Actual power based on the sample (N=11) was .87 for ICM measurements and .91 for BPD scores.

VISTA Medical, 120 Maryland St, Winnipeg, Manitoba, Canada R3G 1L1.

^|| SPSS Inc, 233 S Wacker Dr, Chicago, IL 60606.

	References

Top Abstract Introduction Workstation Exercises:... Evaluation of Workstation... Method Results Discussion Conclusion Appendix References

 

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