The influence of daily physical training on cardiovascular and muscular functions in developing ages were investigated in soccer group (S group: n=12, 11.9±0.1 years of age) and control group (C group: n=14, 11.8±0.1 years of age). Mean values of left ventricular end-diastolic dimension (LVDd) and left ventricular mass, VO₂max and maximal cardiac output determined by treadmill running in S group were significantly higher than those in C group. The mean values of the cross-sectional area of thigh muscles and the maximal strength in knee extension in S group were significantly higher than those in C group. But both mean values of cross-sectional area of lower leg muscles and maximal strength in plantar flexion in S group were not significantly different to those in C group. Significant relationship between the ratio of gastrocnemius muscle in plantar flexor and the LT (lactate threshold) was obtained in both groups. The higher values of the LT for the same G/PF in S group were observed. Highly significant correlations between thigh muscle area and VO₂max or LVDd, and the maximal strength in knee extension and VO₂max or LVDd were found. From these results it is suggested that the development of thigh muscle mass with training such as soccer practice in preadolescent years might contribute not only the increase of muscular strength in knee extension but also cardiorespiratory function and heart morphology.

DESCENTE SPORTS SCIENCE Vol.7/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE