Abstract
This thesis work aims to improve our understanding of the effects of resistance training on performance and skeletal muscle. The dynamic of these effects of training has been apprehended systematically trough tools from systems theory, with 26 rodents resistance trained on a climbing protocol with additional weights. The classical model (Banister et al, 1975) was suitable to analyze the training response (R2 = 0.53, P <0.001). The origin of the very marked performance gains (+ 136% compared to the control group) was investigated among the potential muscle adaptive mechanisms. At the end of the training program, an increase of 123 ± 61% in myosin ATPase activity independent of the phenotype was observed compared to control animals. This increase in myosin ATPase activity seems to occur precisely during the main myosin head isomerization step (i.e. powerstroke) that includes the liberation of the hydrolysis products, and to a lesser extent, during ATP hydrolysis step. A new form of muscular plasticity seems identified. Based on muscle adaptive mechanisms, a new mathematical formulation, more physiological, of the model of the training effects has been proposed and resulted in a better fit (R2 = 0.71, P <0.001). The impulse function of the traditional model has been replaced by an exponential growth function that seems more suitable to analyze both the training response and the adaptations that occur within the muscle tissue as in the contractile units themselves.