Cerebrovascular responses to incremental exercise during hypobaric hypoxia: effect of oxygenation on maximal performance

摘要

cerebral hypoxia has been proposed to be a critical factor limiting exercise performance (37), particularly in hypoxia (7), yet little evidence exists to directly support this theory. Kayser et al. (31) were the first to show that rapidly increasing the fraction of inspired oxygen (FiOz) at the point of maximal exertion prolonged exercise in hypoxia-acclimatized subjects. They concluded that the effect of increased Fio2 was too quick to have reversed metabolic factors associated with peripheral (intramuscular) fatigue and suggested that cerebral reoxygen-ation was a more likely explanation for the improvement in exercise performance. Calbet et al. (11) arrived at similar conclusions after using a comparable model to study factors limiting O2 uptake (V02). They suggested that exercise under hypoxic conditions may have presented a significant threat to cerebral oxygenation; thus cardiac and/or motor output was curtailed to maintain favorable tissue oxygenation status.