n Ergonomics SA : Journal of the Ergonomics Society of South Africa - The effects of task familiarity on performance and strain during a self-paced lifting and lowering task




The concept that self-selected work-rest scheduling and pacing can be an effective tool to prevent fatigue build-up, and therefore overexertion injuries, is relatively unexplored in the literature. Despite the increase in automation in the workplace and forced work pace as a result, there are still many jobs that allow workers to select their own work pace and rest breaks. Numerous factors, such as task familiarity influence a worker's work-rest scheduling. This study is aimed at determining the effects of task familiarity on work-rest scheduling, physiological and subjective strain, as well as work performance in a self-paced lifting and lowering task. Twelve healthy and moderately fit female university students, between 18 and 25 years of age, participated in this study. Participants were required to attend four sessions during which they lifted and lowered a 10 kg crate 120 times at a self-selected work rate, resting whenever and for as long asthey needed. The first session was set as the "unfamiliar" condition. This was followed by two familiarization sessions to ensure that the participants were accustomed to thetask in the last session, set as the "familiar" condition. Work-rest scheduling data, heart rate, electromyographical data, subjective exertion responses and work rate weremeasured during the "unfamiliar" and "familiar" conditions. No data were collected during the second and third sessions. The results showed that task familiarity resulted in significantly (p<0.05) shorter overall working time due to less rest breaks and shorter rest break durations, while overall performance, such as lifting rate, increased.Significant reductions in physiological and perceptual strain were also evident from lower heart rates, EMG responses of the erector spinae, and central and local ratings of perceived exertion under the "familiar" condition.


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