Biomechanical Analysis Of The Standing Long Jump

Introduction
The performance of standing long jump was often adopted to examine the fitness of the school children [1-2], but the test frequently underestimate the subject’s true potential when the subject did not use the best possible technique. The purposes of the present study were to (1) investigate the effects of the arm movement and initial knee joint angle employed in standing long jump by the ground reaction force analysis and three-dimensional motion analysis; and (2) investigate how the jump performance of the female gender related to the body configuration.

Methods
Thirty-four healthy adult females performed standing long jump on a force platform with full effort. Body segment and joint angles were analyzed by three-dimensional motion analysis system. Using kinetic and kinematic data, the trajectories on mass center of body, knee joint angle, magnitude of peak takeoff force, and impulse generation in preparing phase were calculated.

Results
Average standing long jump performances with free arm motion were +1.5 times above performance with restricted arm motion in both knee initial angles. The performances with knee 90o initial flexion were +1.2 times above performance with knee 45o initial flexion in free and restricted arm motions. Judging by trajectories of the center mass of body (COM), free arm motion improves jump distance by anterior displacement of the COM in starting position. The takeoff velocity with 90o knee initial angle was as much as 11% higher than in with 45o knee initial angle. However, the takeoff angles on the COM trajectory showed no significant differences between each other. It was found that starting jump from 90o bend knee relatively extended the time (Graph 1) that the force is applied by the leg muscles. To compare the body configurations and the jumping scores, there were no significant correlations between jump scores and anthropometry data. The greater muscle mass or longer leg did not correlated well with the superior jumping performance.

Discussion / Conclusions
In standing long jump, the takeoff speed and the takeoff angle determine the jump distance. In this study we found the takeoff velocity on the COM trajectory was lower in 45o initial knee angles than in 90o initial knee angles. The takeoff angles on the COM trajectory showed no significant differences between each other. The results showed that jumping with 90o knee initial angle with free arm motion creates the longest distances in standing long jump. This was followed by jumping with 90o initial knee angle with restricted arm motion; 45o initial knee angle with free arm motion; and lastly 45o initial knee angle with restricted arm motion.

References
[1]. Falk B et al. (2001). American Journal of Human Biology, 13(1), 65-70.
[2]. Hebbelinck M et al. (1999). American Journal of Clinical Nutrition, 70(3 Suppl), 579S-585S.

NOTA: O texto com a iconografia está no anexo.

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