Muscle atrophy

Skeletal muscle

Thigh

Radiology

Hindlimb

Leg muscle

Anatomy

Atrophy

Internal medicine

Medial compartment of thigh

Medicine

Physical medicine and rehabilitation

Anterior compartment of thigh

Magnetic resonance imaging

Medicine & Science in Sports & Exercise

ABSTRACT Purpose Musculoskeletal injuries necessitate periods of disuse (i.e., limb immobilization) during which rapid skeletal muscle atrophy occurs. The relative susceptibility of different muscles of the thigh to disuse atrophy remains uninvestigated. We assessed muscle disuse atrophy of individual thigh muscles throughout 1 wk of unilateral knee immobilization. Methods Thirteen healthy, young (20.2 ± 0.6 yr) men underwent 7 d of unilateral leg immobilization via knee bracing. Magnetic resonance imaging scans were performed bilaterally prior to, and following 2 and 7 d of immobilization to determine the volume and anatomical cross-sectional area of the individual muscle groups of the upper legs. Results In contrast to the control leg, total thigh muscle volume had decreased by 1.7% ± 0.3% ( P &lt; 0.01) and 5.5% ± 0.6% ( P &lt; 0.001) in the immobilized leg after 2 and 7 d of disuse, respectively. Muscle loss was significantly greater in the Musculus quadriceps (day 2; 1.7% ± 0.3% ( P &lt; 0.05) and day 7; 6.7% ± 0.6%) when compared with the Musculus hamstrings (day 2; 1.4% ± 0.2% ( P &lt; 0.01) and day 7; 3.5% ± 0.3%) after 7 d of disuse ( P &lt; 0.001). Individual muscles of the thigh exhibited different atrophy rates with the Musculus vastus laterali s anatomical cross-sectional area showing the greater (2.6% ± 0.4% and 7.2% ± 0.8%), and the Musculus gracilis the lesser (1.1% ± 0.7% and 2.3% ± 1.0%) decline following 2 and 7 d of immobilization, respectively ( P &lt; 0.01). Conclusions Thigh muscle disuse atrophy occurs rapidly and is already evident within 2 d of leg immobilization and progresses at a similar rate over the next 5 d (~0.8% muscle loss per day). M. quadriceps muscle shows more atrophy when compared with the M. hamstrings .

Temporal Muscle-specific Disuse Atrophy during One Week of Leg Immobilization