Proceedings of The Physiological Society

The Biomedical Basis of Elite Performance (London) (2012) Proc Physiol Soc 26, PC63

Poster Communications

Characteristics of magnitude and orientation of force in starting block clearance of sprinter and novice

M. Otsuka1, S. Yoshioka1, T. Kurihara1, T. Isaka1

1. Ritsumeikan University, Kusatsu-shi, Japan.

Introduction: Orientation of ground reaction force (GRF) vector of runner is related with acceleration ability (Kugler and Janshen, 2010; Morin et al., 2011), but the orientation of force three-dimensionally is unclear. Therefore, this study clarified that both magnitude and orientation of the force three-dimensionally between sprinter and novice in starting block clearance. Methods: Twelve male sprinters (S) and twelve healthy male students (N) were participated in this study. Movement of whole body and GRF data were captured as each subject was sprinting from pushing starting blocks to 2nd step with 16 high speed cameras (Raptor-E digital 590-1097-RE1; Motion Analysis Corporation, Santa Rosa, CA) and 10 force plates (TF-4060-B; Tech-Gihan, Inc., Japan). Horizontal velocity of center of mass from pushing starting blocks to take-off moment in 2nd step (HV) was utilized as start dash performance. Results: Higher HV of S than N (2.91 ± 0.13 m/s vs. 2.76 ± 0.15 m/s; p < 0.01) was caused by both larger step length (1.05 ± 0.09 m vs. 0.96 ± 0.09 m; p < 0.05) and step frequency (2.25 ± 0.14 Hz vs. 2.04 ± 0.21 Hz; p < 0.05) from pushing starting blocks to 1st step. From take-off of front foot to landing of 1st step, step width of S was larger than that of N (0.27 ± 0.05 m vs. 0.20 ± 0.07 m; p < 0.001), and air-borne time of S was larger than that of N (0.083 ± 0.023 s vs. 0.060 ± 0.028 s; p < 0.05). In pushing starting blocks, mean horizontal (0.92 ± 0.08 N/bw vs. 0.76 ± 0.08 N/bw; p < 0.001), lateral (0.05 ± 0.02 N/bw vs. 0.02 ± 0.03 N/bw; p < 0.01) and vertical forces (1.03 ± 0.06 N/bw vs. 0.95 ± 0.07 N/bw; p < 0.01) of S were larger than those of N. Kugler and Janshen (2010)’s study of physical education students, it was reported that orientation of force was correlated with degree of leaning body forward (r = 0.93). Orientation of the force in sagittal plane at maximal resultant force of S was smaller than that of N during pushing starting blocks (41.9 ± 4.0° vs. 47.4 ± 4.4°; p < 0.01).These suggest that S facilitates greater forward leans of the body than N during pushing starting blocks. In contract, no significant differences of orientation of force in frontal and transverse planes at maximal resultant force were found between S and N during pushing starting blocks. Conclusion: Our findings are summarized as follows: 1) Enough air-borne time to increase step length and horizontal velocity after pushing starting blocks can be achieved by larger magnitude of force; developed leg extension muscles, even if runner leans body forward. 2) Magnitude of lateral force is determinant of larger step width but orientation of the force at pushing blocks from crouching start. Therefore, larger medio-lateral movement is generated naturally during faster sprinting, and sprinter’s orientation of force does not always direct closer to running direction.

Where applicable, experiments conform with Society ethical requirements