Abstract : Intrinsic Ankle and Hopping Leg-Spring Stiff ness in Distance Runners and Aerobic Gymnasts quick-release method which consists of a sudden and fast release of the isometrically contracted muscles. The plasticity of these structures has been widely documented in humans, either directly after hyperactivity [7, 13, 16, 28] , hypoac-tivity [9, 32] or in the disease state [8, 24]. In contrast to the numerous studies which focused exclusively on tendon structures [2, 26, 27, 39] , very few investigations have been carried out to determine the eff ects of intensive sport activity on MT and MA elastic properties in high level sportsmen. In our previous study [38] , higher MT stiff ness in elite long and triple jumpers compared with occasional sportsmen was observed. Recent investigations have shown that leg-spring stiff ness diff ers between athletes in diff erent sport categories [20, 31, 38]. On the basis of EMG analyses, Hobara et al. [20] concluded that the diff erence in leg-spring stiff ness between endurance and power-trained athletes may be largely attributed to diff erences in intrinsic stiff ness of the muscle tendon complex, rather than to altered neural activity. These conclusions are however inconsistent with recent investigations that failed to observe any signifi cant relationships between leg-spring stiff ness during hopping and tendon [29] , MT [38] or MA [34, 38] stiff ness.
