The influence of running velocity, stride characteristics, training background, gender, and caliber of runner on changes in ground contact time in 400-m runs were investigated. Ss (M = 13; F = 4) ran a 400-m time trial on a track, and male sprinters (N = 8) and male endurance athletes (N = 6) ran a simulated 400-m time trial at constant velocity on a treadmill. A special shoe insert was placed in the track spike to determine contact time, and a video recording was used to determine split times for each 40 m. A threshold point of when velocity began to decrease was established.

Velocity degradation was affected by the individual running strategy and reflected fatigue-induced changes in velocity, but was independent of gender, training background, and caliber of athlete. Velocity degradation was accompanied by an increase in ground contact time.

Velocity degradation did not occur in the treadmill tests since velocity remained constant until Ss could no longer perform.

Implication. Treadmill tests do not accurately reflect the performance changes that occur in real-life fatigue.

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