Abstract : The objective of this study was to examine the contribution of intrinsic ankle stiffness to leg-spring stiffness in high level athletes using various musculotendinous solicitations. Eight aerobic gymnasts (G), 10 long-distance runners (R) and 7 controls (C) were evaluated using quick-release or sinusoidal perturbation tests in order to quantify their respective plantarflexor musculotendinous (SI MT), ankle musculoarticular active (SI MA) and passive (K P) stiffness. Leg-spring stiffness (K leg) was measured during vertical hopping. Runners and gymnasts presented significantly higher SI MT values (P<0.01) than controls: 60.4 (±14.1) rad-1 .kg 2/3 for G, 72.7 (±23.8) rad-1 .kg 2/3 for R and 38.8 (±6.5) for C. In addition, normalized K leg were not significantly different between G, R and C. It appeared that intrinsic ankle stiffness had no influence on leg-spring stiffness. The adaptation of SI MT seems to concern specifically the active part of the series elastic component in runners. The results suggested that the number of stretch-shortening cycles during daily practice sessions, rather than their intensity, act as the determinant for this component.
