Discussion
knee brace, immobilization-induced reduction
DISEASE, DISUSE ATROPHY
In the present study, the effect of FOR supplementation were compared with a macronutrient- and energy-matched placebo on indices of muscle size and strength during two weeks of single-leg immobilization in young, healthy men. We discovered that ingestion of FOR prevented the rise in circulating plasma myostatin. However, FOR supplementation did not attenuate the loss of muscle CSA measured by ultrasonography, muscle fiber CSA in type I and II, and LM of the immobilized leg. In addition, both groups did not recover the immobilization-induced reduction in muscle CSA and LM of the immobilized leg after two weeks of returning to normal physical activity. In line with the results of CSA and LM of the immobilized leg, the molecular mechanisms we probed (the number of myostatin-positive SC and the expression of E3 ubiquitin ligases) showed no effect of FOR supplementation, except that phosphorylation of p70S6K was increased post-immobilization in the FOR-SUPP. Isometric peak torque decreased following two weeks of single-leg immobilization; however, two weeks of returning to normal activity was sufficient to recover the reduction in peak torque.Myostatin is a potent negative regulator of muscle growth, and an increased circulating concentration of myostatin has been observed in various conditions, including disease or disuse states [Myostatin circulates in two forms, latent and active, and only activated C-terminal myostatin, after proteolytic processing, can bind to the ActRIIB, thereby initiating signaling, including the pathways activating UPS and inhibiting myogenesis [The mechanisms of FOR on skeletal muscle growth have not been completely determined. However, egg yolk contains macro- and micro-nutrients (lipid, minerals, vitamins, microRNAs, and more) that may modify pathways related to MPS or degradation [After disuse atrophy was induced, the decreased muscle CSA and LM of the immobilized leg were not recovered within 2 weeks of returning to normal activity in both groups (Contrary to muscle mass, the decreased leg extension peak torque was largely recovered by 2 weeks of normal activity recovery (In the present study, daily ingestion of 19.8 g FOR (6wk) did not adversely affect blood variables (Due to the COVID-19 outbreak and the poor compliance with wearing a knee brace, we could not analyze the total number of participants planned to have a medium effect size of power (