Prehabilitation in Older People Undergoing Total Hip Replacement

The goal of this clinical trial is to determine the effect of Resistance Exercise Training (RET)-based (p)rehabilitation versus usual care on skeletal muscle mass and function, as well as on underlying biological processes, in older adults undergoing elective Total Hip Replacement (THR) due to severe Osteoarthritis (OA). The main questions it aims to answer are: * What is the effects of RET-based (p)rehabilitation versus usual care to improve muscle mass and function in patients undergoing elective unilateral THR surgery for end-stage OA? * What is the potential of certain circulating biomarkers to predict the efficacy of the musculoskeletal system response to RET in patients with severe OA? Researchers will compare RET-based (p)rehabilitation versus usual care to see if RET works to increase skeletal muscle mass and function. Participants in the usual care group will undergo standard rehabilitation (12 weeks post-surgery), and participants in the (p)rehabilitation group will undergo RET-based full-body (p)rehabilitation (3x/week) for 2 weeks pre-surgery and 12 weeks post-surgery.