The objective of this thesis was to document the response in horses to high-intensity exercise and antioxidant supplementation. In a pilot study, horses underwent an exercise test. Plasma and synovial fluid (SF) samples were taken 24 hr prior to exercise (BL), 0.5, 1, 2, 4, 8, and 24 hr following exercise. High-intensity exercise in horses resulted in a transient systemic inflammatory state and articular inflammation and cartilage breakdown. In a subsequent study, horses were provided with a supplement comprised of Cucumis melo pulp extract to determine whether antioxidant supplementation impacted parameters of exercise-induced systemic or articular inflammation/oxidative stress. Based on the prior time course, samples were taken at BL, 1 and 24 hr following exercise. Supplementation resulted in post-exercise mitigation of articular oxidative stress and cartilage breakdown, increased antioxidant status, reduced blood lymphocyte levels, and 24 hr following high-intensity exercise supplemented horses displayed reduced inflammation and muscle breakdown.