Musculoskeletal injury, particularly injuries requiring surgical repair, induce significant muscle atrophy, resulting in diminished physical function. The protein turnover-associated (diminished protein synthesis, elevated protein breakdown, negative net muscle protein balance) etiology of injury and surgical-induced atrophy are, in part, similar to those observed with muscle wasting induced by hyper-catabolic and inflammatory conditions and prolonged periods of skeletal muscle disuse (e.g., cachexia and joint immobilization). Combining dietary strategies to optimize the anabolic properties of beef as a high quality protein source that provides essential amino acids prior to surgery and throughout post-surgery rehabilitation may attenuate muscle atrophy and accelerate the restoration of muscle function. This project will examine the efficacy of habitual consumption of a beef-based higher protein meal pattern and post-physical rehabilitation beef protein supplementation throughout post-surgical rehabilitation intervention on skeletal muscle function in response to anterior cruciate ligament (ACL) repair in healthy, physically active adults.

Stable isotope methodologies, proteomic analysis of muscle protein synthesis, and molecular assessments of skeletal muscle atrophy and remodeling will be assessed to evaluate the effects of increased protein intake, including consumption of a high quality beef-based protein supplement following patient physical therapy sessions on:

1. Skeletal muscle protein fractional synthetic rates during and in recovery from surgery;
2. Inflammatory, proteolytic, and anabolic intramuscular signaling during surgery and their association with skeletal muscle protein synthesis and muscle function;
3. Muscle size and functional recovery;
4. Duration to return to routine exercise, sport, or physical activity.

Inclusion Criteria:

• 18 to 50 years of age
• identified as appropriate for study recruitment by their respective orthopedic surgeon
• undergoing their first anterior cruciate ligament (ACL) repair
• undergo ACL reconstruction under general anesthesia
• body mass indexes (BMIs) within normal to overweight ranges

Exclusion Criteria:

• reporting metabolic or cardiovascular abnormalities, food allergies, gastrointestinal disorders (i.e. lactose intolerance)
• use of nutritional/herbal/sports supplements including anabolic steroids, and tobacco products will be excluded from the study
• BMIs above 29.9