title: Differential atrophy of the lower-limb musculature during prolonged bed-rest.
abstract: Patients with medical, orthopaedic and surgical conditions are often assigned to bed-rest and/or immobilised in orthopaedic devices. Although such conditions lead to muscle atrophy, no studies have yet considered differential atrophy of the lower-limb musculature during inactivity to enable the development of rehabilitative exercise programmes. Bed-rest is a model used to simulate the effects of spaceflight and physical inactivity. Ten male subjects underwent 56-days of bed-rest. Magnetic resonance imaging of the lower-limbs was performed at 2-weekly intervals during bed-rest. Volume of individual muscles of the lower-limb and subsequently, rates of atrophy were calculated. Rates of atrophy differed (F = 7.4, p < 0.0001) between the muscles with the greatest rates of atrophy seen in the medial gastrocnemius, soleus and vastii (p < 0.00000002). The hamstring muscles were also affected (p < 0.00015). Atrophy was less in the ankle dorsiflexors and anteromedial hip muscles (p > 0.081). Differential rates of atrophy were seen in synergistic muscles (e.g. adductor magnus > adductor longus, p = 0.009; medial gastrocnemius > lateral gastrocnemius, p = 0.002; vastii > rectus femoris, p = 0.0002). These results demonstrate that muscle imbalances can occur after extended periods of reduced postural muscle activity, potentially hampering recovery on return to full upright body position. Such deconditioned patients should be prescribed "closed-chain" simulated resistance exercises, which target the lower-limb antigravity extensor muscles which were most affected in bed-rest.
authors.affiliation: Centre for Muscle and Bone Research, Charité Campus Benjamin Franklin, Free University and Humboldt-University Berlin, Hindenburgdamm 30, 12200 Berlin, Germany. belavy@gmail.com
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Belavý
authors.forename: Tanja
authors.initials: T
authors.lastname: Miokovic
authors.forename: Gabriele
authors.initials: G
authors.lastname: Armbrecht
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Richardson
authors.forename: Jörn
authors.initials: J
authors.lastname: Rittweger
authors.forename: Dieter
authors.initials: D
authors.lastname: Felsenberg
mesh_terms: D000328:Adult; D001510:Bed Rest / Q000009:adverse effects*; D006801:Humans; D035002:Lower Extremity / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D018482:Muscle, Skeletal / Q000473:pathology; D009133:Muscular Atrophy / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D009929:Organ Size; D011859:Radiography; D013848:Thigh / Q000000981:diagnostic imaging / Q000473:pathology; D013997:Time Factors
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