Neuromuscular aspects in development of exercise countermeasures.
Based on the results generated from experiments conducted by our investigators, it is clear that prolonged exposure to microgravity environments can induce ultrastructural abnormalities and atrophy of muscle and impair muscle function, especially upon return to terrestrial gravity. It is also apparent that ground-base models can be effectively used to study these changes. This provides a less expensive and more controlled laboratory condition in order to conduct experiments. The use of animal models must be more closely examined. In the case of muscle adaptations to microgravity, the data from flight experiments which have used rodents might suggest the use of exercise with characteristics contrary to those which would be most appropriate to defend against atrophy and dysfunction in human muscle. Although many spaceflight experiments may be limited to the use of animal models, the results of the studies reviewed in this paper emphasize the importance of using human models in order to provide the most accurate interpretation of data for the development of exercise countermeasures for spaceflight. If maintenance of muscle structure, size and function is perceived as operationally necessary, the results from the studies conducted by our investigators indicate that the use of more resistive exercise must be given greater consideration as part of the development of future exercise countermeasure programs for spaceflight. The advantages of incorporating resistive exercise with a strong emphasis on the use of eccentric muscle actions in addition to concentric actions may prove most effective as a countermeasure against the muscle atrophy and dysfunction caused by long-duration exposure to microgravity environments.
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National Aeronautics and Space Administration, Biomedical Operations and Research Office, Kennedy Space Center, FL 32899.
D000328:Adult; D001510:Bed Rest / Q000009:adverse effects; D005081:Exercise Therapy; D006801:Humans; D008297:Male; D009133:Muscular Atrophy / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D009469:Neuromuscular Junction / Q000503:physiopathology; D013026:Space Flight; D014893:Weightlessness / Q000009:adverse effects*