Kinematic differences between faster and slower sprinters during the acceleration phase of sprint running

Aim: The purpose of this study was to examine kinematic differences between faster and slower sprinters during the acceleration phase of sprint running. Methods: Nineteen collegiate sprinters were divided into FAST (N.=9) and SLOW (N.=10) groups, based on their best 100 m race times. A two-dimensional videographic technique was used to record the side views of 40 m sprint performances using four high-speed digital camcorders. Using the recorded images, kinematic variables such as contact time, flight time, horizontal velocity, and horizontal acceleration were determined from the 1^st step to the 19^th step. A two-way repeated measures ANOVA (two groups of 10 steps each) with a Tukey post-hoc test was used to analyze the obtained data. Results: From the 7^th step to the 19^th step, the horizontal velocity was significantly higher for the FAST group as compared with that for the SLOW group. The horizontal acceleration from the 1^st step to the 19^th step and the horizontal velocity from the 7^th step to the 19^th step were significantly greater for the FAST group as compared with those for the SLOW group. In addition, the ground contact time was significantly lower for the FAST group as compared with that for the SLOW group. Conclusion: The results indicate that faster sprinters can achieve greater horizontal acceleration with shorter ground contact during the initial as well as the latter stage of the acceleration phase, during which they are already running faster.