Effects of workload level and 8-versus 12-h workday duration on test battery performance

It is generally agreed that workday durations of 12 h or more are not advis able where workload levels are very high. However, there is no clear resear ch basis for the identification of workload levels which should preclude th e introduction of extended shifts. In the present study, the effects of var ying workload levels and shift durations were investigated both in the labo ratory and in a workplace. In the laboratory study subjects performed eithe r cognitive work (two workload levels) or physically demanding work (heart rare maintained at 35 beats/min above resting), and there were significant effects of both shift duration and workload level on various performance te sts, bodily discomfort, hand steadiness and alertness. In the physically de manding condition, perceived workload was higher on 12 h days despite heart rare being unchanged. In a field study, 34 workers participating for three days each, half of them on 8 h days and half on 12-h days, workload data w ere obtained for each subject at each half-day data collection point. The c ombination of higher workload and 12-h workdays produced greater fatigue, a s manifested in increased bodily discomfort, decreased alertness, decreased hand steadiness and increased errors on the grammatical reasoning task. In addition to these interacting effects of workload and work duration, there were main effects of both workload and work duration on bodily discomfort, and of workload on hand steadiness. Relevance to industry The results have relevance for managers and employees regarding the adoptio n of extended shift systems, particularly in relation to the nature of job demands, overall workload levels, and the criticality of human performance for system safety and efficiency. (C) 2000 Elsevier Science B.V. All rights reserved.