Physiological adaptation to a high level of habitual physical activity during adolescence.

This paper deals with studies of adaptations of physiological characteristics to a high level of habitual physical activity during adolescence. A comparative approach was used involving investigations of a group of male champion swimmers at the age of 17 and a randomized sample of boys of similar age, not active in competitive sport and drawn from the general population. Metabolic, respiratory, and circulatory response pattern to graded bicycle work was assessed. Maximal oxygen uptake averaged 20% higher in swimmers than in ordinary boys. Respiratory response pattern was similar at sub-maximal work, but the swimmers reached higher values in maximal exercise. Transfer factor for carbon monoxide increased in linear fashion to the increase in cardiac output, and was higher at rest as well as in maximal exercise for the swimmers. The transfer factor levelled off at a work rate of about 70% of maximal oxygen uptake in the ordinary school boys, while no levelling off was observed in the swimmers. Cardiac output was closely the same at rest and in sub-maximal exercise for the two groups, but the swimmers reached higher values. Stroke volume was higher for the swimmers and the heart rate correspondingly lower at all metabolic levels. Systemic arterial pressure response were closely the same at sub-maximal work rates in the two groups, but the swimmers reached higher values in maximal exercise. [ABSTRACT FROM AUTHOR]