The aim of this study is to observe the effect of running speed on stride frequency, stride length, oxygen debt and integrated EMG activity during sprint running. Eight male subjects performed 100m running at three different submaximal and maximal speeds. These results were summarized as follows : (1) Stride frequency increased curve linearly with an increase of running speed. Stride length increased until 80% of maximal running speed, however it decreased slightly above that speed. (2) It was observed the curve linear relatioship (r=0.906) between oxygen debt (% of the highest value) and running speed (% of maximal speed). The regression equation was Y=2.2・10^X^, where Y is oxygen debt and X is running speed. (3) The correlation coefficient between oxygen debt and maximal running speed was 0.913 (p<0.001), also a significant correlation (r=0.923, p<0.001) was found between oxygen debt and stride frequency. (4) The EMG activity and integrated EMG of four muscles were obtained from lower extremities by means of telemetering during running at various speeds. Each integrated EMG activity from four muscle groups increased with increase of running speed or stride frequency or both. (5) The curve linear relationship was found between integrated EMG activity and running speed for three muscles (m. rectus femoris, m. biceps femoris, m. tibialis anterior), however a significant linear relationship (r=0.965, p<0.001) was obtained from only m. gastrocnemius. (6) A higher significant correlation coefficient was found between integrated EMG and oxygen debt for m. rectus femoris (p<0.001), m. biceps femoris (p<0.05), and m. tibialis anterior (p<0.001). The increase of integrated EMG for m. gastrocnemius indicated a different pattern compared to other muscle
