Exercise loading of tendons and the development of overuse injuries. A review of current literature.

This review examines recent studies on the effects of exercise on tendons in animal models. Although tendon adaptation to exercise has been described using histology, morphometry, ultrasonography and molecular biology, precise measurements of excess tendon loading during exercise protocols have not been reported. Only a few studies have attempted to evaluate the mechanical strength of exercised tendons. The long term effect of exercise on tendons appears to be positive, but researchers have suggested that periods of mechanical weakness occur in tendons during adaptation to loading conditions. Studies documenting changes associated with the terminal state of pathological tendons are also summarised. Unfortunately, there are no descriptions of tendon tissue in the early stages of overuse injury. Since blood flow is commonly implicated in the emergence of tendinitis, the final section covers recent work on blood flow and tendon physiology. Related research identifying cellular mediators (hyperthermia, hypoxia, and oxidative stress) involved in the development of tendinitis is also presented. Suggestions for further research into exercise loading and the development of tendon overuse injuries are made.