The modern warfighter faces numerous physiological challenges including sleep deprivation, sustained intense physical activity, and caloric restriction, the combined effects of which may result in the loss of lean body mass and decreased physical performance. Dietary interventions may help preserve lean body mass and facilitate recovery from periods of intense physical demand. For example, dietary strategies that increase amino acid availability have been shown to stimulate protein synthesis in skeletal muscle following resistance exercise. Because military tasks also incorporate endurance exercise components, studies regarding the effects of increasing dietary amino acids following endurance exercise are warranted. The objectives of this study are to characterize the effect of endurance exercise on protein synthesis and breakdown as well as the ability of an essential amino acid supplement to influence skeletal muscle protein metabolism and its cellular and molecular regulation following endurance exercise.

Inclusion Criteria:

• Men and women aged 18 - 35 years
• Weight stable
• Recreationally active with VO2max of 40 - 50 ml/kg/min
• Refrain from taking any NSAIDS or any aspirin-containing medications
• Supervisor approval if a federal employee

Exclusion Criteria:

• Disease or medication that affects macronutrient metabolism and/or the ability to participate in strenuous exercise
• Allergies to foods or medications (including, but not limited to, lidocaine or phenylalanine) to be utilized in the study
• Abnormal PT/PTT test or problems with blood clotting
• Present condition of alcoholism or other substance abuse that compromises exercise capacity
• Musculoskeletal injuries that compromise the ability to exercise
• Pregnancy