Protein dose effects on muscle during five days of one-leg immobilization

The Effects of Varying Protein Intakes on Muscle Protein Synthesis During Injury-Mediated Muscle Disuse

This test compares 20 grams versus 40 grams of whey protein to see which dose better preserves muscle protein synthesis in healthy 18–39-year-olds during five days of one-leg immobilization.

Quick facts

• Phase: NA
• Study type: Interventional
• Enrollment: 28 (estimated)
• Ages: 17 Years to 39 Years
• Sex: All
• Sponsor: United States Army Research Institute of Environmental Medicine (fed)
• Locations: 1 site (Natick, Massachusetts)
• Trial ID: NCT07069426 on ClinicalTrials.gov

What this trial studies

Healthy, recreationally active men and women aged 18–39 will be randomized in a double-blind, parallel design to receive either 20 g or 40 g of whey protein after five days of unilateral leg immobilization. Immobilization is achieved with a rigid knee brace set at about 60° of flexion while participants ambulate with crutches and consume a standardized diet. At the end of the immobilization period participants undergo a protein feeding protocol with primed, continuous stable isotope infusions, serial blood draws, and muscle biopsies from both the immobilized and control legs. Muscle protein synthesis responses to the two protein doses will be compared to determine whether a higher protein dose overcomes disuse-induced anabolic resistance.

Who should consider this trial

Good fit: Ideal participants are healthy, recreationally active men and women aged 18–39 with BMI 18.5–32 kg/m2 who can safely use crutches, follow a standardized diet, and tolerate muscle biopsies.

Not a fit: People outside the age or BMI ranges, those with musculoskeletal injuries that prevent safe crutch use, older adults, or individuals with chronic health conditions are unlikely to receive direct benefit from this protocol.

Why it matters

Potential benefit: If successful, the findings could identify a protein dosing strategy that helps preserve muscle mass and speed recovery after short-term limb immobilization.

How similar studies have performed: Previous protein supplementation studies during disuse have produced mixed results, and this direct 20 g versus 40 g dose comparison using stable isotope tracers and biopsies is a relatively novel way to clarify effective protein amounts.

Eligibility criteria

Inclusion Criteria:

* Men and women aged 18-39 years (17-39 years if military personnel)
* Body mass index (BMI) between 18.5-32 kg/m2
* 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), and dietary supplements (i.e., vitamin D, probiotics) 24 hours before and during immobilization and final testing day.
* Willing to only consume caffeine products provided by study staff during the study.
* Supervisor approval for federal civilian employees and non-SRV active-duty military personnel stationed at 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., 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, cardiovascular disease, Crohn's disease, etc.).
* Taking medication that affects macronutrient utilization (i.e., statins, corticosteroids, weight loss medications such as Ozempic, etc.).
* Significantly abnormal blood clotting as determined by USARIEM Office of Medical Oversight (OMSO) or home duty station medical support (HMS).
* Allergy to lidocaine (or similar local anesthetic).
* Present condition of alcoholism, anabolic steroid use, or other substance abuse issues as determined by OMSO or HMS.
* Blood donation within 8-wk of beginning the study.
* Pregnant, trying to become pregnant, and/or breastfeeding (results of urine pregnancy test and self-report for breastfeeding will be obtained before body composition testing).
* Unwilling or unable to consume study diets or foods provided due to personal preference and/or food allergies.
* Unwilling or unable to adhere to study physical restrictions (i.e., no structured physical activity or recreational activity beyond activities of daily living) 24 hours before and during immobilization, and the final testing day.
* Unwilling or unable to keep the knee brace on and walk with crutches during the immobilization phase.

Where this trial is running

Natick, Massachusetts

• US Army Research Institute of Environmental Medicine — Natick, Massachusetts, United States (RECRUITING)

Study contacts

• Study coordinator: Emily E Howard, PhD

Conditions: Muscle Disuse, Muscle Disuse Atrophy, muscle protein synthesis, muscle disuse, muscle disuse atrophy, immobilization, anabolic resistance, dose-response