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

• Published in: Medicine and science in sports and exercise 2020-04, Vol.52 (4), p.944-954
• Main Authors: KILROE, SEAN P., FULFORD, JONATHAN, JACKMAN, SARAH R., VAN LOON, LUC J. C., WALL, BENJAMIN T.
• Format: Article
• Language: English
• Subjects: Braces; Exercise Test; Hamstring Muscles - diagnostic imaging; Hamstring Muscles - pathology; Humans; Immobilization - adverse effects; Magnetic Resonance Imaging; Male; Muscle Strength; Muscular Atrophy - diagnostic imaging; Muscular Atrophy - etiology; Muscular Atrophy - pathology; Quadriceps Muscle - diagnostic imaging; Quadriceps Muscle - pathology; Time Factors; Young Adult
• ISSN: 0195-9131; 1530-0315
• DOI: 10.1249/MSS.0000000000002200

PURPOSEMusculoskeletal 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. METHODSThirteen 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. RESULTSIn contrast to the control leg, total thigh muscle volume had decreased by 1.7% ± 0.3% (P < 0.01) and 5.5% ± 0.6% (P < 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 < 0.05) and day 7; 6.7% ± 0.6%) when compared with the Musculus hamstrings (day 2; 1.4% ± 0.2% (P < 0.01) and day 7; 3.5% ± 0.3%) after 7 d of disuse (P < 0.001). Individual muscles of the thigh exhibited different atrophy rates with the Musculus vastus lateralis 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 < 0.01). CONCLUSIONSThigh 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.