Does initial skeletal muscle size or sex affect the magnitude of muscle loss in response to 14 days immobilization?

We aimed to determine if there was a relationship between pre-immobilization skeletal muscle size and the magnitude of muscle atrophy following 14 d of unilateral lower limb immobilization. Our findings (n=30) show that pre-immobilization leg fat-free mass and quadriceps cross-sectional area (CSA) were unrelated to the magnitude of muscle atrophy. However, sex-based differences may be present, but confirmatory work is required. In women, pre-immobilization leg fat-free mass and CSA were associated with changes in quadriceps CSA after immobilization (n=9, r²=0.54-0.68; P<0.05). The extent of muscle atrophy is not affected by initial muscle mass, but there is potential for sex-based differences.