The influence of task variation on manifestation of fatigue is ambiguous – a literature review

Task variation has been proposed to reduce shoulder fatigue resulting from repetitive hand–arm tasks. This review analyses the effect of task variation, both ‘temporal (i.e. change of work–rest ratio)’ and ‘activity (i.e. job rotation)’ variation, on physiological responses, endurance time (ET) and subjective feelings. Pubmed was searched and complemented with references from selected articles, resulting in 17 articles. Temporal variation had some positive effects on the objective parameters, as blood pressure decreased and ET increased, and on the subjective feelings, as perceived discomfort decreased. The observed findings of activity variation showed both positive and negative effects of increased activity variation, while hardly any effects were found on electromyography manifestations of fatigue. In conclusion, the evidence for positive effects of increasing the level of variation is scarce. The number of studies on variation is limited, while in most studies the findings were not controlled for the amount or intensity of work. Practitioner Summary: Some laboratory-controlled studies showed some positive effects of increasing temporal variation, providing limited support for introducing frequent interruptions in work. Activity variation showed ambiguous effects, meaning there is no evidence for practical implication. In practice, however, other positive effects of activity variation may occur, for example job enrichment and increased motivation.