Influence of physical activity on the strength of knee ligaments in rats

Abstract

The relationship between physical activity and the strength of the medial collateral ligament was investigated with normal and hypophysectomized rats. Animals were assigned to groups designated as controls, single exercise period, repeated exercise periods (trained), trained-detrained, immobilized, tenectomized, hypophysectomized-trained, and hypophy sec torn ized-trained plus growth hormone. Results were expressed in units of separation force (SF), separation force-to-body weight ratio (SFR), and centimeters of ligamentous elongation. The findings indicated that a single exercise bout had no appreciable influence on SF results, but that repeated periods of exercise will significantly strengthen knee ligaments. The same tendency prevailed with the detrained group. Ligaments from tenectomized and immobilized animals had SF values lower than their controls; however, only the latter finding had statistical significance. Force-elongation curves showed that the normal trained animals had more elongation at a given force than nontrained animals. It was postulated that the changes associated with training were occurring at the attachment site between the ligament and the bone.