Endurance training and cardiovascular function in 9-and 10-year-old boys.

Thirty-two boys, 9 and 10 years old, were randomly divided into experimental and control groups in order to investigate cardiovascular responses to interval cycle training. The experimental group exercised on a cycle ergometer 5 days a week during their physical education periods. There were 4 work bouts of 4 minutes each, separated by 3-minute recovery intervals each day for 8 weeks. Loads were prescribed so that heart rates ranged from 170 to 195 for each bout (80--90% estimated maximum). The control group took part in a traditional sports-oriented physical education period during this time. Pretest steady-state values at HR130 were determined for oxygen consumption, heart rate, and cardiac output, after which the load was progressively increased to determine physical work capacity at heart rate 170. The tests were repeated after the 8-week training period, at work loads identical to pretest values. Analysis of covariance revealed that significant improvements in the experimental group occurred in stroke volume and oxygen pulse. The 6.5% increase in stroke volume was countered by a 6.8% decrease in heart rate, resulting in no differences in cardiac output. Increases in physical work capacity occurred in each group, but only that of the experimental group was significant. No differences were detected for either group in steady state oxygen consumption or calculated arteriovenous oxygen difference. It was concluded that children of this age level adapt readily to cardiovascular stress. It was suggested that if improvement in cardiovascular fitness is considered to be a valid goal of physical education, then the traditional sports and games should be supplemented by training procedures designed specifically for endurance.