Cardiorespiratory functions in children with high and low performances in endurance running.

To elucidate the characteristics of cardiorespiratory functions during exercise in young children in relation to their performances in endurance running. Twenty six 6-hear-old children participated in the present study. They were divided into two groups (fast and slow) from the results of three endurance performances (1,500 m, 4,000 m, and 8,850 m). Maximal oxygen uptake VO2max) in the fast group (X +/- SD; 45.3 +/- 5.5 ml x kg-1 x min-1) was significantly greater (p less than 0.05) than the slow group (39.8 +/- 5.9 ml x kg-1 x min-1). The performances in endurance running were also significantly different between the two groups (p less than 0.01). There was, therefore, a significant correlation between VO2max and endurance performance in 6-year-old children (p less than 0.05 or p less than 0.01), but the relationship was less than that of adults. During endurance running, the heart rate of the best performer stayed constant, while that of the worst performer decreased. This may indicate that the worst performer used a smaller percentage of VO2max, which might be derived from a lower motivation for running. In conclusion, endurance performances in 6-year-old children was influenced by VO2max as well as by the constant mobilization of cardiorespiratory functions throughout endurance running, probably due to high motivation.