Influence des propriétés musculaires sur un exercice de locomotion humaine : de l'efficience à la déficience motrice

• Bieuzen François

The purpose of the present work is to determine the influence of the muscular properties of the lower limbs on the locomotor pattern. The first studies (studies n°l and n°2) analyse the relationship between the strength capacity of the lower extremity muscles and the choice of a particular locomotor pattern during cycling. Our results indicate that, on healthy subject, the locomotor pattern is not affected by the muscular characteristics. On the other hand, the muscular properties modify the synergy of the muscle coordination and the criteria of energy and neuromusoular efficiency during locomotion. The three following studies (3, 4 and 4bis) aim to characterize the effects of various muscular alterations on locomotion. Two methods are used to generate these alterations. The first consists to generate a muscular fatigue from two types of repeated lower limbs contractions (concentric vs. eccentric) (Study 3). The second method is comparative, and aims to analyze the effects of a fatiguing exercise on the locomotion in two populations with different muscular properties (young vs. elderly adults) (Studies 4 and 4bis). The results of the study 3 show, on the one hand, that muscular alterations are directly dependent on the type of contraction and, on the other hand, that these alterations specifically modify the locomotor pattern. The two last studies produce two original results, The first result indicates that the alteration of the muscular properties after a fatiguing exercise is potentiated when the subjects have a preliminary muscular insufficiency. The second result shows that, whatever the characteristics of the muscular function, the modification of the locomotor pattern after a fatiguing exercise is always the same. However, this adaptation is accompanied by a reorganization of the muscular cooperation specific to each population. The whole of this experimental work suggests that the muscular properties of the lower limbs, altered or not, do not influence the kinematics of the locomotor pattern. However, they could determine a particular organization of the muscular synergies to produce the movement