Abstract EN:

All the investigations included in this thesis aim at determining the interactions existing between ventilation (considered here as the disturbing factor) and postural stability, and to analyze the double contribution of the abdominal muscles to the ventilation and the postural adjustments. The first chapter aims at joining together the current knowledge necessary to the comprehension of the objectives and the development of the methodology. We approach successively the mechanisms implied in breathing, the methods of the respiratory analysis and the respiratory adaptations related to the physical exercise in order to determine the characteristics of the hyperventilation imposed on the subjects. We also introduce the mechanisms of postural adjustments and their modes of study, necessary to justify the choice of parameters which can characterize the postural disturbances related to hyperventilation. Lastly, the whole variety of knowledge concerning the abdominal muscles on the anatomical and functional slope is presented there. In a second chapter, we propose a methodology associating, in an original way, techniques of surface electromyography, stabilometry, used in the temporal and spectral domain, and the collection of the respiratory gas exchange. The first experimental phase, whose finality is to establish normative values, consists in determining the respiratory capacities of the population by means of spirometric tests and the neuromuscular capacities of the abdominal muscles by the establishment of EMG-torque relationships, from which an index of neuromuscular efficiency was extracted. The second experimental phase attempts to put forward the modifications of the body sway related to the ventilatory disturbances imposed by an induced hyperventilation and a voluntary hyperventilation. The results show that ventilation is considered as a source of potential disturbance for the postural control system whose importance will depend on the individual characteristics, the posturo-kinetic capacity and the ventilatory request. Indeed, we put forward that hyperventilation is accompanied by an increase in the parameters stabilometric expressing a reduction in the postural stability whose importance is related to that of hyperventilation. These disturbances are expressed not only in the sagittal plane but also in the frontal plane. The analysis of the ventilatory, mechanical and electromyographic parameters shows the double and complex contribution of the abdominal muscles in the control of ventilation and the postural adjustments set up to compensate the disturbing effects related to hyperventilation. Since the abdominal muscles appeared sensitive to two individual characteristics: gender and sporting practice, we propose in this prospect to establish the link between the contribution of the abdominal muscles to the postural adjustments and ventilation, and the indexes of neuromuscular efficiency obtained for various populations for which an optimization or a deficiency of the abdominal muscles is awaited