The purpose of this study was to investigate the eŠects of fatigue on ground reaction forces and leg kinetics during all-out 600 m running. Eight male middle-distance runners were asked to perform two kinds of running, i.e. an all-out 600 m run and a non-fatigued 80 m run with the same velocity as at the 550 m mark of the 600 m run. Their running motion was videotaped and the ground reaction forces were measured at the 150 m and 550 m marks of the 600 m run and at the 50 m mark of the 80 m run. The step length, ground reaction forces, ankle plantar ‰exion torque, and knee extension torque of the support leg decreased due to fatigue. The hip joint torque of the recovery leg decreased due to the diŠerence in running speed rather than fatigue. From these results, we suggest that in theˆnal stage of 800 m race, a runner should not try to extend the step length by thrusting against the ground with the support leg but should maintain the step time as much as possible by moving the recovery leg quickly.
There are two techniques for a lateral sprint start: crossover (CS) and jab step (JS) starts. This study aimed to elucidate the difference in the CS and JS starts in terms of sprint performance and leg kinetics in athletes from ball-and-goal type sports (e.g. soccer and handball). Nineteen male athletes performed CS and JS starts, during which their motion and the force they applied to the ground were simultaneously recorded using a motion-capture system and two force platforms. The results showed that, although 5-m time via video analysis did not differ between CS and JS starts, forward velocity of centre of gravity (CG) and normalised average horizontal external power were greater for the JS start than the CS start. From waveform analysis, greater positive joint power in the sagittal plane leading to greater positive work in the JS start were found in the first three quarters of the push-off phase for rear hip extension and in the subsequent push-off phase for rear ankle plantar flexion. In conclusion, the results suggest that the JS start is superior to the CS start for start quickness, though the gains in the start did not appear to transfer to the 5-m performance. Moreover, greater positive joint power in the first three quarters of the push-off phase for the rear hip extension and in the subsequent push-off phase for the rear ankle plantar flexion were considered to be important contributing factors to the better performance of the JS start.
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