Muscle elastic properties during wrist flexion and extension in healthy sedentary subjects and volley-ball players.

The aim of this study was to determine the effects of gender and chronic hyperactivity (training) on musculo-tendinous stiffness and joint flexibility and to examine in vivo whether those stiffness parameters were correlated. Thus, maximal isometric voluntary contraction, series elastic stiffness during wrist flexion and wrist extension, and wrist flexibility were investigated in healthy sedentary subjects and in women volley-ball players. Maximal isometric contraction and flexibility were measured classically with specific ergometers. Moreover, muscle stiffness measurements were performed thanks to the use of quick-release movements of the wrist, which had previously been maintained in isometric contraction, allowing the calculation of a musculo-tendinous stiffness index. Despite significant differences in maximal voluntary contraction between wrist flexors and wrist extensors for each of the groups tested and between men and women, no significant gender, function or training effects were found upon musculo-tendinous stiffness indices. Flexibility assessments in both women groups demonstrated that active to passive ratios for wrist flexion remain unchanged whereas a significant training-induced increase for wrist extension was observed. Moreover, no significant relationship between women active joint flexibility and musculo-tendinous stiffness indices was found (r(2): 0.0004 - 0.0319, p > 0.05) whatever the muscle function tested. Collectively, the present results suggest that neural factors rather than morphological changes (i. e. muscle architecture and fiber composition) may explain predominantly the functional consequences observed in wrist extension associated with volley-ball training. Moreover, both musculo-tendinous stiffness and joint flexibility give different information about wrist functional status.