The impact of rest breaks on temporal trends in injury risk

This study examined the impact of rest breaks on temporal trends in industrial accident risks in an attempt to replicate earlier findings of a linear increase in risk as a function of elapsed time on task. In two separate studies, the trend in work-related injuries were studied in relation to the timing of rest breaks. In study one, comparisons were made between on- and off-track workers on weekly rotating three-shift systems operating in a large engineering company. Records of on-duty injuries that occurred over 12 months were examined (N = 4645 incidents). Study two involved interviewing patients who had suffered work-related hand injuries in a variety of occupational settings (N = 407 patients). Hierarchical log linear analysis was used in both studies. In study one, risk increased from the first to the second half-hour of continuous work following a break, but then remained relatively constant in subsequent half-hour periods, although there was a fall in the third half-hour for on-track workers. In some of the data, there was also a decrease in risk in the period leading up to the end of a work period. There was a sharp decline in reported injuries toward the very end of a shift, but otherwise the observed trends did not differ between successive periods of continuous work or between morning, afternoon, and night shifts. In study two, risk increased from the first to the second half-hour of continuous work and then remained relatively constant in the third half-hour. The contrast between the current and previous findings may be due to the relatively unique work environment of the previous study. It is suggested that the current trends reflect the effects of working in a relatively unconstrained task environment, and that causes other than fatigue may underlie the trends observed in both the previous and current studies.