A MATHEMATICAL MODEL OF SKELETAL MUSCLE METABOLISM. SIMULATIONS OF EXERCISE RESPONSES AFTER SPACE TRAVEL AND ENDURANCE TRAINING

摘要

Space travel has detrimental effects on skeletal muscle metabolism and function, as well as on physical working capacity. Intensive endurance training programs conducted while traveling in space may reverse some of the metabolic adaptations induced by space travel and compensate for the loss of aerobic capacity. To quantitatively understand the interaction between muscle metabolic adaptations and exercise responses after periods of space travel or endurance training, we developed a mathematical model of skeletal muscle metabolism to predict exercise responses in the detrained and trained states, respectively. Computer simulations of a stepwise change in work rate of moderate intensity on a cycle ergometer showed larger changes in [PCr]/[Cr] and [ADP]/[ATP] in detrained muscle, as well as slower dynamics. Pyruvate oxidation was 9% greater in detrained muscle, while fat oxidation was 7% higher in trained muscle. Muscle oxygen uptake on-transient response was 29% faster in trained (τ = 0.25 min) than in detrained muscle (τ =0.45 min). In general, exercise responses in the trained state displayed "compensatory" behavior than those in the detrained state when compared to simulations of exercise responses in normal control subjects. Thus, endurance training can in fact counteract some of the deleterious metabolic adaptations induced by space travel.