Analysis of the Horizontal Ground Reaction Forces in Sprinters

Abstract

Recent studies suggest that in sprinters, horizontal forces are more relevant for a better performance than vertical forces. However, differences in the horizontal forces patterns in ground reaction force in athletes of different performance levels remain unclear. PURPOSE: To determine the dynamometric differences in the horizontal forces patterns between fast and slow sprinters. METHODS: 11 sprinters (5 female, age=19.3±1.6) from regional and national level were divided in two groups, according to their personal best in 60 meters(m) (group 1: n=6 fast; group 2: n=5 slow). All subjects performed 10 maximal valid 30m sprints, in order to assess ground reaction forces using a force platform (Bertec 406015). The time of the relevant moments in the force curves, the forces magnitude, the angles and the ground reaction impulses of the support phase of the athletes were determined using Matlab (2002b). All data were normalized according to athlete´s body weight and Mann-Whitney test was used to comparisons between groups, using SPSS (20.0). RESULTS: Data showed that (i) group 1 promoted significative higher propulsive forces than group 2 (0.75±0.09 vs. 0.64±0.06 / U=4 P=0.05); (ii) the ratio between propulsive time and braking time were significantly different between groups 1 and 2 (1.302±0.14 vs. 1.190±0.05, respectively / U=4.5 p=0.05); (iii) significant differences were found for braking forces when comparing the two groups (-1.31±0.20 vs. -1.10±0.09 for groups 1 and 2 respectively / U=4 p=0.05). CONCLUSION: The differences in the patterns of the horizontal curves of the ground reaction force in slow and fast athletes are the magnitude of propulsive force production, the time spent in propulsive phase and the braking forces. It seems that, the technical ability of force application might be a determinant factor for sprint performance.