Elsevier

Applied Ergonomics

Volume 32, Issue 3, June 2001, Pages 225-237
Applied Ergonomics

Computer terminal work and the benefit of microbreaks

https://doi.org/10.1016/S0003-6870(00)00071-5Get rights and content

Abstract

Microbreaks are scheduled rest breaks taken to prevent the onset or progression of cumulative trauma disorders in the computerized workstation environment. The authors examined the benefit of microbreaks by investigating myoelectric signal (MES) behavior, perceived discomfort, and worker productivity while individuals performed their usual keying work. Participants were randomly assigned to one of three experimental groups. Each participant provided data from working sessions where they took no breaks, and from working sessions where they took breaks according to their group assignment: microbreaks at their own discretion (control), microbreaks at 20 min intervals, and microbreaks at 40 min intervals. Four main muscle areas were studied: the cervical extensors, the lumbar erector spinae, the upper trapezius/supraspinatus, and the wrist and finger extensors. The authors have previously shown that when computer workers remained seated at their workstation, the muscles performing sustained postural contractions displayed a cyclic trend in the mean frequency (MNF) of the MES (McLean et al., J. Electrophysiol. Kinesiol. 10 (1) (2000) 33). The data provided evidence (p<0.05) that all microbreak protocols were associated with a higher frequency of MNF cycling at the wrist extensors, at the neck when microbreaks were taken by the control and 40 min protocol groups, and at the back when breaks were taken by the 20 and 40 min protocol groups. No significant change in the frequency of MNF cycling was noted at the shoulder. It was determined (p<0.05) that microbreaks had a positive effect on reducing discomfort in all areas studied during computer terminal work, particularly when breaks were taken at 20 min intervals. Finally, microbreaks showed no evidence of a detrimental effect on worker productivity. The underlying cause of MNF cycling, and its relationship to the development of discomfort or cumulative trauma disorders remains to be determined.

Introduction

As a result of the technological advancements of today's workplace, many office workers no longer need to leave their desks in order to perform many time-inefficient tasks of the past, such as copying documents, sending and receiving mail and filing. Accordingly, computer terminal workers now face prolonged periods of sustained seated postures accompanied by long periods of keyboard data entry. With the benefits of this technology (increased productivity and high speed information transfer) has come the added cost of cumulative trauma disorders (CTDs). The incidence of CTDs in computerized workstation environments is on the rise (Bammer, 1987; Bergqvist et al., 1995; Bernard et al., 1994), which is due, among other factors, to the maintenance of sustained postures, which affect the low back, the upper limb and neck (Sauter, 1991; Nelson and Silverstein, 1998). Repetitive keyboard and mouse use places workers at risk of muscle, tendon, and nerve damage (James et al., 1997; Marcus, 1996). Despite the provision of appropriate furniture and workstation setup, many workers complain of musculoskeletal pain. Pain is generally a warning signal. It tells us that what we are doing is likely to cause damage (or further damage) in the future. The warning signs experienced by computer terminal operators are often precursors to chronic problems including musculoskeletal pain, headaches, and even nerve compression syndromes.

It is often recommended that computer workers take frequent, short breaks from their work in order to prevent the onset of discomfort (Fisher et al., 1993; Sundelin and Hagberg, 1989; Schreuer et al., 1996). The recommended interval between breaks ranges anywhere from 5 min (Floru et al., 1985) to 1 h (Henning et al., 1997), depending on the researcher, ergonomist, physiotherapist, or doctor. Similarly the ideal duration of the breaks remains elusive. Henning et al. (1989) found that data entry operators took, on average, breaks of 27.4 s in duration when they were asked to resume the data entry task when they felt ready to continue after the break. Questions remain, however, regarding the break time required for adequate rest or recovery to take place.

When told to take frequent breaks throughout the work day, many workers fear that this will impact negatively on their work, or that it will impact on their manager's (or co-workers’) perception of their effort. Additionally if breaks are regimented, this may result in added stress due to frequent work interruption. In order to describe a successful ergonomic intervention, it is important to determine that the intervention will actually benefit the employer as well as the employee (McLean and Rickards, 1998). In order to gain support by the workers, microbreaks must increase the level of comfort experienced during work tasks, or must assist with productivity when incentives or quotas are in place. In order to gain support by management, the concept of microbreaks must show no detrimental effect on worker productivity, while preferably causing an increase in long-term productivity or a reduction in costs related to worker turnover or absenteeism.

The purpose of this work was to investigate myoelectric signal (MES) activity and perceived discomfort in areas of common CTD complaints: the neck, the low back, the shoulder region, and the wrist. In particular, the first objective was to determine the effect of “microbreak” protocols on muscle activation behavior. The second objective was to determine the effect of “microbreaks” on perceived discomfort. The third objective was to determine the effect of “microbreaks” on worker productivity. It was hypothesized that microbreaks would be associated with an increase in the frequency of MNF cycling in the MES, would reduce the level of perceived discomfort, and would not negatively impact worker productivity.

Section snippets

Methodology

The study was reviewed and accepted by the University of New Brunswick Ethics Committee. Fifteen participants were recruited by word of mouth from the accounting (6) and library (6) offices at the University of New Brunswick, and from New Brunswick Provincial Government Offices (3) in Fredericton, NB, Canada. All participants were recruited based on their performance of jobs that involved sustained sitting postures in conjunction with keying and data entry tasks. All participants were female

Myoelectric signal behavior

MNF cycling was investigated by counting directional frequency changes in the smoothed MNF data records. An example of a typical smoothed MNF record is presented in Fig. 2. If the smoothed MNF increased or decreased by an interval of at least 5 Hz, and leveled off and again shifted by at least 5 Hz, this phenomenon was counted as one cycle. MNF cycling was deemed present if a minimum of one cycle per hour was noted in the smoothed MNF data record. Tingley and McLean (2001) provide details

Discussion

The presence of cycling behavior in the MES data remained consistent with previous work by the authors (McLean et al., 1997). MNF cycling may explain the controversy in the literature regarding the effect of fatigue on the MES recorded during low level contractions. Some authors have reported a positive-going slope of MNF vs. time when MES was recorded from low level contractions (Arendt-Neilsen et al., 1989; Hansson et al., 1992), while others have reported a negative-going slope (Jorgensen,

Conclusions

The major contribution of this work is the determination of the beneficial effect of regularly scheduled “microbreaks” on subjective discomfort ratings at the neck, the low back, the shoulder, and the forearm/wrist areas. In addition, this work contributes evidence that the implementation of such a strategy has no detrimental effect on worker productivity. Finally, this work provides evidence that most individuals demonstrate a cyclic behavior in the MNF of their MES in the cervical extensors,

Acknowledgments

The authors thank the Natural Sciences and Engineering Research Council of Canada, and the Workplace Health, Safety and Compensation Commission of New Brunswick for their financial support throughout this work.

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