The goal of this study is to determine if an oral provision of amino acids will enhance exercise-induced increases in markers of Achilles tendon collagen production.

Tendon pain is a common complaint in older adults. The mechanisms contributing to the large number of tendon problems in older adults are not known. It has been shown that tendon cross-sectional area (CSA) is reduced with aging concurrent with a significant loss of tendon collagen. Exercise is used to reverse the loss of muscle mass with aging but surprisingly exercise interventions designed to reduce tendon problems in older people are relatively unexplored. In young adults, exercise stimulates tendon collagen synthesis and enhances the production of growth factors, which stimulate tendon collagen production. It is presumed that exercise-induced increase in collagen synthesis contributes to the increase in tendon stiffness and CSA noted in young adults after chronic resistance exercise (RE). In contrast, our preliminary work indicates that RE is not effective at reducing the effects of aging on tendon. The investigators have demonstrated that 12-weeks of RE does not lead to increases in tendon CSA or stiffness, even when skeletal muscle mass and strength are greatly enhanced. To prevent tendon injury, greater tendon CSA and stiffness aid in withstanding the force generated by trained skeletal muscle. Greater CSA and stiffness also optimize force transfer through tendon to maximize musculoskeletal function. Our findings indicate that RE is not an optimal intervention for reversing age-related changes in tendon properties. Novel interventions are clearly needed that will enhance collagen synthesis leading to an increase in tendon stiffness and CSA while also improving skeletal muscle mass and strength in older individuals. This study will evaluate the effectiveness of various methods for stimulating tendon collagen synthesis during a bout of acute exercise. Specifically, the investigators propose two approaches to this problem.

1. An acute bout of cycling exercise will enhance the release of growth factors leading to a larger increase in tendon collagen synthesis.
2. A bolus of amino acids given orally will increase the release of key stimulators of tendon collagen synthesis leading to enhanced collagen synthesis after acute exercise.

Inclusion Criteria:

• 21-35 years or 60-80 years old

Exclusion Criteria:

• diabetes
• BMI>35
• acute illness, cardiac, pulmonary, liver, or kidney abnormalities, uncontrolled hypertension, metabolic disorders, arthritis, or a history of neuromuscular problems.
• chronic pain medication users
• alcoholism
• competitive athletes
• pregnant women will be excluded
• Individuals with specific allergies to amino acids