Computer terminal work and the benefit of microbreaks
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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