The Effects of Age and Physique on Continuous-Work Capacity

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Abstract
The following hypotheses were investigated: (1) continuous-work capacity does not decrease with increasing age, and (2) physique has a greater effect on continuous-work capacity during slower, heavier tasks than during faster, lighter tasks. Twenty-eight, healthy male subjects, 14 between 25 and 35 years of age, and 14 between 45 and 60, performed 54 manual handling tasks for a duration of 40 min. Three lifting, three lowering, four pushing, one pulling, and six carrying tasks were performed at three different rates of work. Three replications of a walking task were also performed. The continuous-work capacity of each subject for each task was measured by a psychophysical technique which required subjects to adjust their work loads to the maximum amount that they could perform without strain or discomfort, and without becoming tired, weakened, overheated, or out of breath. Heart rates were monitored continuously during task performance. The age hypothesis was tested by subjecting both work-load and heart-rate data to analyses of variance. The physique hypothesis was tested by correlating work-load data with each of 41 anthropometric measurements obtained from each subject. The results supported the age hypothesis. The physique hypothesis, however, was supported only by the results of the younger group of subjects.