MINIMIZING FATIGUE DURING REPETITIVE JOBS - OPTIMAL WORK-REST SCHEDULES

Twenty women were asked to generate forces using a dynamometer that we re consistent with one of three different work-rest schedules (a low-, medium-, and high-force schedule). Each work-rest schedule consisted of 6 identical blocks of 10 work-rest cycles. Each of the 10 work-rest cycles lasted 1 min. The first work-rest cycle in each block consiste d of a 6-s maximal voluntary contraction and a 54-s rest. The remainin g 9 work-rest cycles in each block consisted of a submaximal contracti on and a rest period. The desired force of the submaximal contraction, the length of this contraction, and the duration of the rest period r emained constant within schedules but varied across schedules. The amo unt of physiological work was kept constant among schedules. The fatig ue that developed in the medium-force schedule was significantly lower than that developed in either the low- or high-force schedule. A mode l was developed that predicted the amount of fatiguable strength at th e beginning and end of each contraction of a work-rest cycle. When fit to the results from the experiment, the model explained 94% of the va riance. The model can be used to predict the work-rest schedule that m inimizes fatigue in a given repetitive job, thereby potentially increa sing productivity and reducing the incidence of cumulative trauma diso rders.