[Functional status of respiratory muscles and physical endurance among women under prolonged hypokinesia]

Validity of the hypothesis for the role of the respiratory muscles in deterioration of physical work capacity following long-term hypokinesia was tested. Experiments were performed with participation of 8 female subjects aged from 27 to 36 years in the 120-day head-down bed rest. Physical performance and functional status of the respiratory muscles have been determined during incremental loading on bicycle ergometer with normal respiration and breathing against additional external resistance. Functional deficit of the respiratory muscles due to long-term bed rest was shown not to allow adequate ventilation and gas exchange at submaximal loads. This resulted in dyspnea, hypoventilation-induced decrease in oxygen consumption and carbon dioxide release, hypercapnia, and lowered threshold of anaerobic metabolism which, in parallel with the deconditioning of the cardiovascular system and the skeletal anti-g musculature, were responsible for degradation of aerobic physical work capacity.