Effects of Exercise on Achilles Tendon Healing in a Rat Model

Abstract

The effects of motion, or lack of it, on Achilles tendon healing are not well defined. We have recently shown that immobilization has a detrimental effect on tendon healing in a rat model. The aim of this experiment was to determine whether enforced exercise had an additional beneficial effect on the mechanical and functional recovery of divided Achilles tendons in rats. Male Sprague-Dawley rats were randomly allocated into a nonexercise and an exercise group (N = 10 for each group). In both groups the right Achilles tendon was surgically transected. The left, uninjured lower limb served as an internal control. Both groups of animals were housed under identical conditions with the exception that the exercise group swam for 15 minutes per day. Functional performance was determined from the measurement of hindpaw prints of walking rats preoperatively and on alternate postoperative days. On day 15, the animals were killed and weighed, and biomechanical evaluations were performed on both the injured and uninjured Achilles tendon constructs. There were no differences in weight at time of death. All animals had an initial functional deficit that returned to near-normal by day 15. There were significant differences in the morphological and the mechanical properties of the healing Achilles tendon constructs at day 15 when comparing the injured with the uninjured Achilles tendon constructs. Supplemental exercise, however, had no effect on the functional or mechanical recovery of injured or uninjured Achilles tendons in the rat model.