| The metabolic and biochemical adaptations which set the endurance limit in skeletal muscle and are modified by physical training, and those which set the fatigue limits in conditions of chronic hypoxia, are not completely understood. Therefore, the purpose of this study was to measure the key metabolites involved in the control of oxidative and glycolytic metabolism, during the elevated metabolic demands of exercise, in subject groups which were separated by distinct differences in their training status or by their exposure to chronic hypobaric hypoxia. Since repeated measures of the key metabolites involved in energy metabolism (PCr, Pi, ATP) and intracellular pH (pH;The calf ergometer was used to compare sedentary lowlanders, marathon and ultramarathon runners, power trained athletes, and Quechua Indians, native to altitudes of 4,200 m in the Andes, before and after deacclimation to sea level. It was found that the Andean natives did not possess a standard physiological phenotype with respect to aerobic and anaerobic capacities. In addition, given the Andean's very low anaerobic capacity and intermediate aerobic capacity, this group performed calf work equivalent to that of highly trained endurance and power athletes. Moreover, pH;The results of the experiments using the electrical stimulation model indicate that RF coil geometry, stimulation intensity and duty cycle, electrode placement, and subject tolerance require very close control for the model to be reliable. It is felt that this model is best suited for experiments which require a within-subject design and is ideally suited for experimental or therapeutic intervention studies. |
