Molecular Mechanisms Underlying Anabolic Resistance to Protein Intake During Muscle Disuse

Inclusion Criteria: * Men and women aged 18-39 years. * Body mass index (BMI) between 18.5-30 kg/m2 * Healthy without evidence of chronic illness (e.g., diabetes, cardiovascular disease, Crohn's disease) or musculoskeletal injury as determined by the USARIEM Office of Medical Oversight (OMSO) or home duty station medical support. * Routinely participate in aerobic and/or resistance exercise at least 2 days per week. * Willing to refrain from alcohol, smoking, smokeless nicotine products (includes e-cigarettes, vaping, chewing tobacco), caffeine, and dietary supplements (i.e., vitamin D, probiotics) during the run-in diet, immobilization phase, and final testing day of the study. * Supervisor approval for federal civilian employees and non-human research volunteer (HRV) active-duty military personnel stationed at Natick Soldier System Center (NSSC). * Biological females must have normal menstrual cycles between 26-32 days in duration; 5 menstrual cycles within the past 6 months; or on continuous hormonal contraception (i.e., intrauteraine device (IUD) or oral contraceptives without placebo). Exclusion Criteria: * Musculoskeletal injuries that may interfere with the safe use of crutches. * Personal or family history of thrombosis, or prior diagnosis of deep vein thrombosis (DVT) or pulmonary embolism (PE). * Metabolic or cardiovascular abnormalities, gastrointestinal disorders, neuromuscular disorders, lower-limb amputation, or muscle/bone wasting disorders (e.g., diabetes, …