The purpose of this investigation was to determine whether alterations in physical activity would modify the repair process of ligaments as evaluated by tissue DNA, collagen synthesis, and tensile strength. Compared to immobilization, progressive exercise markedly enhanced the healing process by inducing a more rapid return of tissue DNA, collagen synthesis, and separation force to within "normal" limits. Exercise also significantly increased wet and dry weights of repaired ligaments whereas immobilization markedly decreased these measurements because of the change in total collagen content. However, it remains uncertain whether progressive exercise can cause a shift in the equilibrium rates between collagen synthesis and collagen degradation.