Influence of physical exercise on aging rats: II. Life-long exercise delays aging of tail tendon collagen.

Regular physical exercise has been shown to have a number of benefits compared with sedentary behaviour, such as delaying a number of aging changes and increasing the life expectancy but not the maximum lifespan. The purpose of this paper is to analyze the effects of physical exercise on the connective tissues of the body, especially systemic effects. We trained male Sprague-Dawley rats in a treadmill from the age of 5 months to 23 months. We analyzed the effects of training on tail tendons with respect to thermal stability of collagen and biomechanical properties of tendon bundles. Although tail tendons are attached to muscles, the are not weight-bearing as limb muscle tendons and can, therefore, be considered to be subjected mainly to systemic effects. The thermal stability of tail tendon collagen was significantly lower or "younger' for the trained group compared with the sedentary one. The biomechanical parameters were likewise "younger' with respect to maximum stress, although considerably stiffer compared with a 5-month-old base-line group. This suggests that there are several mechanisms, elicited by physical exercise, that act on the connective tissues. It can be concluded that life-long physical exercise has a beneficial influence on the connective tissues of the maturing and aging organism.