BUCHANAN, C.I.; MARSH, R.L.: Effects of Exercise on the Biomechanical Properties of Tendon.

Tendon has been shown to undergo remodeling in response to strength or endurance training, however, compared to muscle, studies of the effects of exercise on tendon are quite limited. Biomechanical parameters that may change in response to exercise are tensile strength, stiffness and fatigability. However, the information that is available is inconsistent. Studies that have examined mechanical changes of tendon in response to endurance training suggest that ultimate failure strength and stiffness increase with training. In contrast, strength-training regimes do not appear to increase tendon stiffness. The majority of tendon studies have been restricted to measuring stiffness of the free-tendon, however the mechanical properties as well as adaptability of tendon may differ in the aponeurosis versus the free- tendon. Those studies that have measured stiffness of the combined free-tendon and aponeurosis have found that stiffness of the aponeurosis-free-tendon unit increases with exercise. However, values for stiffness are lower than values obtained in studies conducted on isolated free-tendons. The adaptive significance of changes in tendon with exercise is unclear. Possible reasons for changing stiffness are to alter elastic energy storage or to alter the ultimate failure strength of the tendon in response to increased loading. Alternately, we suggest that increase in tendon stiffness observed following endurance training represents a mechanism to resist tendon damage due to mechanical fatigue associated with repeated application of stress. Supported by NIH grants AR39318 and AR47337.