“Functional age” and physical work capacity during day and night

Abstract

Borg and Linderholm (1967) showed that the body’s response to physical work is dependent on age, as is the subjective perception of the work load. They asked their subjects to rate the perceived exertion (the RPE measure) during submaximal work on a cycle ergometer simultaneously monitored heart rate (the HR measure). Significant age differences were found, in that the older subjects had a lower HR and a higher RPE than the younger subjects (fig.l). In a study of interindividual differences in circadian fatigue patterns of shift workers, Östberg (1973) made use of Borg and Linderholm’s technique, and found that a subject’s change in HR/RPE pattern from day to night was similar to what would have been observed had first a young and then an old subject been tested in the day. Changed HR/RPE pattern could thus tentatively be evaluated in terms of changed “functional age” for the same subject. Employing this hypothesis it was found that ‘morning’ types of subjects were ‘young’ in the mornings and ‘old’ in the evenings, and vice versa for ‘evening’ types of subjects (‘morning’ and ‘evening’ types being defined by their scores on a simple questionnaire on circadian phase).