Mechanical and electrical adaptation of skeletal muscle to gravitational unloading.
The physiological and biochemical properties of limb skeletal muscle have been shown to adapt to variety of experimental conditions.  Among these is the microgravity encountered with spaceflight.  It is adaptations accompanying skeletal muscle disuse atrophy.  Foremost among these changes is a reduction in the force-generating capacity, which is presumably a direct result of decrease in fiber number and diameter.  These changes suggest a spaceflight-induced reduction in muscle work capacity.  The interesting finding that the reduction of the mechanical tension is not proportional to the reduction of muscle weight, fiber diameter, and concentration of contractile protein suggested that changes of electrical activity might contribute to the reduction of the contraction force in disused muscle.  The purpose of our study was to assess the effects of a 7-d "dry" immersion on the contractile properties of the triceps surae muscle.
Koryak
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Institute of Biomedical Problems, Moscow, Russia.
D000200:Action Potentials; D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D019054:Evoked Potentials, Motor / Q000502:physiology; D006801:Humans; D007101:Immersion / Q000009:adverse effects*; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*