Sex-specific Determinants of Early-phase Recovery From Skeletal Muscle Disuse

The negative health consequences of muscular disuse in aging populations are unequivocal. While descriptive, outcome data on disuse and recovery are abundant, key knowledge gaps limit researcher's ability to implement evidence-based, rehabilitation strategies. Limiters include: i) an inability to identify individuals most susceptible to disuse, ii) insufficient information to differentiate between, and respond to, disuse atrophy in men and women, iii) limited insight into the mechanisms driving adaptation to early rehabilitative exercise, and iv) the assumption that disused and healthy skeletal muscle will have a similar, positive response to resistance exercise. The investigators will complete a 2-phase, randomized clinical trial. The protocol includes 7-days of unilateral leg disuse (ULD; Phase 1), immediately followed by 1 week of bilateral leg rehabilitation (Phase 2). Healthy, middle-aged men (n=40) and (post-menopausal) women (n=40), (50-65 y) will be recruited; a neglected research demographic who present with a largely youthful phenotype, but are at risk of accelerated disuse atrophy. This project will provide a highly powered, detailed phenotypic characterization of the continuum of adults most and least susceptible to muscular disuse. Clinical outcomes will be supported by RNA deep sequencing and pathway analysis to establish a platform that: i) improves scientists' ability to identify higher-risk individuals and ii) provides insight into time-sensitive, sex-specific and effective rehabilitation strategies. Findings and reposed molecular data from this study, may help identify future therapeutic targets and serve as an uncomplicated/comorbidity-free baseline for clinical trials in populations experiencing disuse atrophy.