The spring-mass system is a reasonable model of the whole phenomenon of musculotendinous stiffness of the lower limbs. This study was to investigate the developmental effect on jumping techniques and lower-limb stiffness during vertical jumping. Nine children and nine adults participated in the study. A Peak high-speed camera was synchronized with a Kistler force plate (600Hz) to collect the biomechanics parameters. Differences between mean values were analyzed by a t-test for independent samples. The present research showed that during down ward countermovement, the 18-year-old group produced a larger displacement of ankle, knee, and CG in crouch phase (p < .05) and higher vertical ground reaction forces, whereas the CG was lowest (p <. 05), and that the group produced greater leg and joint stiffness (p <. 05) to create larger elastic energy generation and storage. For the 6-year-old group, the lower extremity could not be extended completely during push phase. Thus, the lack of prestretch, lower stiffness, and incomplete extension in the 6-year-old group is thought to influence jumping performance.
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