The purpose of this investigation was to examine the influence of running velocity, stride characteristics, training background, gender, and caliber of a runner on the changes in ground contact time during a 400-m run. Thirteen male and 4 female sprinters ran a 400-m time trial on the track, and 8 male sprinters and 6 male endurance athletes ran a simulated 400-m trial at constant velocity on the treadmill. A special shoe insert was placed in the track spike to determine contact time, and a video camera was used to determine split times for each 40 m. Two threshold points were identified during the 400-m run, with the first occurring when the running velocity began to decrease. The threshold points were affected by the individual running strategy and reflected fatigue-induced changes in the running velocity; they also were independent of gender, training background, and caliber of an athlete.
Ari Nummela and Heikki Rusko are with the Research Institute for Olympic Sports, Rautpohjankatu 6, FIN-40700 Jyvӓskyiӓ, Finland. James Stray-Gundersen is with Baylor/University of Texas Southwestern Sports Science and Research Center, 411 North Washington, Suite 3000, Dallas, TX 75246.