Résumé :
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Communication n° 364 Introduction : The nervous system has to combine step length (L) and frequency (f) in order to adjust the velocity of the centre of foot pressure (CP), expressed as v=Lf, to the one of the centre of gravity at the end of gait initiation, expressed as V. Locomotor parameter programming has yet to be considered through: a) its objective, i.e., the adjustment of both velocities which is a necessary condition to an adequate progression of the body and b) the strategy used in order to achieve this objective, i.e., the respective contributions of L and f to CP velocity. Objective : In this study, we wanted to know if a neuromuscular disease could change this programming. Methods : Gait initiation was performed on a force plate by a control group and by a patient group presenting Becker Myopathy. We analysed the motor performance in terms of V, the adjustment of both velocities and used the differential method (Couillandre and Brenière, 2003) to analyse the strategy. Results : The motor performance was diminished in the patient group (VP = 0.988m/s versus VC = 1.322m/s). However, for both groups, V and v were adjusted at the end of the first step. Morover, step length and frequency had different contributions to CP velocity from one group to another, step frequency being the parameter that contributed the most to CP velocity in the patient group. Conclusion : These results suggest that the nervous system, despite the diminution of gait speed linked to the motor deficit induced by the pathology, introduces specific changes on step length and frequency, in order to preserve the adjustment of CP to CG velocity. The differential method could be useful in the follow up of a disease, where one could see modifications of the strategy.
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