An interventional study of 20 grams protein and 40 grams protein in Muscle Disuse and Muscle Disuse Atrophy, sponsored by United States Army Research Institute of Environmental Medicine. Recruiting at 1 site in United States. Open to participants aged 17 Years to 39 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-09-11.
Sponsored by United States Army Research Institute of Environmental Medicine · Not applicable, Interventional, and Basic science
Individuals who sustain musculoskeletal injuries (MSKI) can experience a rapid loss of muscle mass due to declines in muscle loading and activation that occur post-injury (i.e., disuse atrophy). Loss of muscle under these conditions is attributed to a persistent negative net muscle protein balance (muscle protein synthesis [MPS] \< muscle protein breakdown) that results, in part, from declines in postprandial MPS (i.e., anabolic resistance). Nutritional interventions that enhance postprandial MPS may be used to overcome disuse-induced anabolic resistance and preserve muscle mass to accelerate recovery and improve recovery outcomes. While supplemental protein has been explored as a potential countermeasure to disuse-induce anabolic resistance, the observed efficacy of such interventions has been mixed. Equivocal findings across studies may be attributed, in part, to an insufficient understanding of what constitutes an effective protein-based intervention. Importantly, no study to date has determined an optimal protein dose for overcoming disuse-induce anabolic resistance, or if there is a threshold for maximally stimulating postprandial MPS under disuse conditions. Therefore, the objective of this work is to determine rates of MPS at rest and in response to standard (20 g) or high (40 g) doses of whey protein during knee immobilization (DISUSE) compared with standard activity (ACTIVE)
Healthy, recreationally active men and women will complete this randomized, double-blind, parallel study. Muscle disuse will be implemented for five days using a unilateral leg immobilization model with one leg assigned to immobilization (DISUSE) and the contralateral leg used as a control (ACTIVE). Immobilization will be implemented with a rigid knee brace fixed at \~60° of flexion and participants will ambulate using crutches. Diets will be standardized during the immobilization phase. Participants will complete a protein feeding study at the end of immobilization consisting of primed, continuous stable isotope infusions, serial blood draws, and muscle biopsies. MPS will be assessed in both the DISUSE and ACTIVE legs in response to standard (20 g) or high (40 g) doses of whey protein. Findings from this work will directly inform the development of targeted nutritional countermeasures for overcoming disuse-induced anabolic resistance and preserving muscle mass after MSKI to optimize physical performance recovery.
Exclusion Criteria:
Participants will consume 20 g of whey protein after 5 days of muscle disuse
Dietary Supplement: 20 grams protein
Participants will consume 40 g of whey protein after 5 days of muscle disuse
Dietary Supplement: 40 grams protein
20 grams of whey protein provided as beverage
40 grams of whey protein provided as beverage
Rates of postabsorptive and postprandial muscle protein synthesis assessed using 2H5-Phenylalanine stable isotope methodologies.
Postabsorptive and postprandial muscle protein synthesis in response to 20 or 40 g of whey protein determined using 2H5-Phenylalanine stable isotope methodologies and expressed as fractional synthetic rate (FSR).
Time frame: After 5 days of muscle disuse
Plan to share: No — Individual participant data will not be shared.
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United States Army Research Institute of Environmental Medicine