Abstract
The influence of daily physical exercise on oxygen utilizing capacity of working muscle investigated by means of measureing lactate threshold (LT) during progressive treadmill running from the comparison between 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) . LT1 was determined as the point where blood lactate concentration (La) increased from rest level, and LT2 was determined by the gradient, La/VO2. body weight-1 (2 mM/10 ml. kg-1, min-1) .
LT1 and LT2 in S group were significantly higher than those in C group expressed with absolute and relative values of VO2 (1. min-1, ml. kg-1. min-1, % VO2max) . No significant differences in La, ventilation responses, and heart rate at the point of LT1 and LT2 were observed between S and C group, La showed slight decrease and was kept at lower level in S group with increase of VO2, compared with C group. On the contrary, La in C group began to increase at lower level of VO2. From our previous longitudinal study of LT in non-athletic children, we observed that LT shifted to lower level with growth. It was sugesed that La curve of S group, such shift had not occurred. Differences of these patterns in VO2 and La between athletic children and non-athletic children were similar to those observed in adults athletes and non-athletes.
In conclusion it was supposed that sufficient daily physical training in 10-12 year of age might increase oxygen utilizing capacity of leg working muscle during running exercise.
