In Vivo Alterations in Skeletal Muscle Form and Function after Disuse Atrophy

CLARK. B. C. In Vivo Alterations in Skeletal Muscle Form and Function after Disuse Atrophy, Med. Sci. Sports Exerc., Vol. 41, No. 10, pp. 1869-1875, 2009. Prolonged reductions in muscle activity and mechanical loading (e.g., bed rest, cast immobilization) result in alterations in skeletal muscle form and function. The purpose of this review article was to synthesize recent findings from several Studies on the dramatic effects of disuse on skeletal muscle morphology and muscle performance in humans. Specifically, the following are discussed: 1) how the antigravity muscles are most susceptible to atrophy and how the degree of atrophy varies between Muscle groups: 2) how disuse alters muscle composition by increasing intermuscular adipose tissue 3) the influence of different disuse models on regulating the loss of muscle mass and strength, with immobilization causing greater reductions than bed rest and limb Suspension do; 4) the observation that disuse decreases strength to a greater extent than muscle mass and the role of adaptations in both neural and contractile properties that influences this excessive loss of strength; 5) the equivocal findings oil the effect of disuse oil muscle fatigue resistance and 6) the reduction in motor control after prolonged disuse. Lastly, emerging data warranting further inquiry into the modulating role of biological sex on disuse-induced adaptations ire also discussed.