A study was conducted to investigate the relationships among changes of joint torque of the lower limbs, sprint ability such as sprint speed, stride length and stride frequency in 400 m running, and muscular endurance of the lower limbs. Subjects were 11 male track and field athletes who had a 400m running time of 48.75±1.32s. The experiment was composed of videotaping sprint form at 160 m and 360 m points during 400 m running, and measuring muscular endurance of hip and knee flexion and extension using Cybex NormTM.
The main results were as follows:
1) There was a significant relationship between 400 m running time and ability to maintain a higher running speed at the 360 m point.
2) Running speed, stride length and stride frequency decreased significantly at the 360 m point.
3) Subjects who showed a smaller decrease in stride frequency at the 360 m could maintain higher running speed.
4) Subjects who showed smaller decrease in maximal joint torque of the lower limbs at the 360 m could maintain a higher running speed.
5) There was a significant relationship between an increase in support time and decrease in maximal joint torque of hip extension for the recovery leg.
6) Ability to maintain joint torque during 400 m running was influenced by muscular endurance of the lower limbs.
These results suggest that the ability to maintain torque needed for higher performance in 400 m running is influenced by muscular endurance of the lower limbs.

Purpose of this study was to examine the recovery process of delayed onset muscle soreness, jump performance, force to contact with the ground and lower limbs movement after intensive jump exercise (IJE), and the relationships between muscle soreness, changes of jump performance and lower limbs movement. Nine males who have experience in special jump exercise participated in this study voluntarily. For the measurement, subjective investigation of the muscle soreness, drop jump performance using a 30 cm high box [jump height, contact time and drop jump index (jump height / contact time)], ground reaction force and movements of lower limbs. This measurement was carried out before IJE (Pre), and at 4 hours (P4), 24 hours (P24) and 72 hours (P72) after IJE. Main results are as follows ; at the time of P24 when intense muscle soreness appeared, significant jump height decreases and contact time increases were shown, and the jump index decreased markedly. This decrease of performance correlated to the change of knee and ankle joint movements during the eccentric phase. At P4, for a subject who felt strong muscle soreness, the decrease of jump height and jump index were considerable. At P72, most subjects recovered to the levels of jump height and contact time to the Pre level. The findings reveal that the jump performances are related to the degree of delayed onset muscle soreness.

The purpose of this study was to investigate the effects of different sitting postures, by change of seat height, on lower extremity muscle activation and maximum power during explosive bicycle pedaling exercises. The subjects performed 5 sec maximum pedaling exercises at three different seat heights.‘High’ seat height was defined as 95% of leg length, ‘Middle’ was 90% and‘Low’ was 85%.
The results were summarized as follows: A) At 3 revolutions, maximum power at‘High’ was significantly higher than that at‘low’. B) Pelvic angle at‘High’ was significantly higher than that at‘Low’. C) The maximum extension angle of the knee joint was a significantly high value in descend. ing order of‘High’, ‘Middle’ and‘Low’. D) mEMG of the Erector spinae and Biceps femoris at‘High’ was significantly higher than that at‘Low’. E) At‘High’, there was a significant correlation between maximum power of 3 revolutions and mEMG in the Gluteus maximus. In addition, maximum power at 3 revolutions tended to correlate with mEMG in the Biceps femoris and Vastus lateralis.
These results suggest that in explosive pedaling exercises, different sitting postures by change of seat height, have different influences on hip extension muscle activation and maximum power.