Objective: In this study we investigated the effects of different intensities of therapeutic laser energy and running exercise, and their combined effects on the repair of Achilles tendons in rats.
Materials and methods: Thirty-six mature Sprague-Dawley rats that received surgical hemi-transection of their right Achilles tendon were tested. Three laser dosages (4 J/cm2, 1 J/cm2 and 0 J/cm2) and three running periods (30 min, 15 min, and 0 min) resulting in nine different dosage and time groups were studied with four rats in each group. The treatments were given on alternate days starting on day 5 post-injury. On day 22, the tendons were tested for load-relaxation, stiffness, and ultimate strength.
Results: There was a significant effect of laser energy on normalized load-relaxation, the rats receiving 4 J/cm2 had less load-relaxation than those receiving no laser treatment (p = 0.05). Results of stiffness testing revealed a significant effect, and rats that ran for 30 min had more stiffness than those that did not run (p = 0.015). For ultimate strength, due to a significant interaction (p = 0.05), the two factors were analyzed separately, and the results showed that for rats receiving no laser therapy, those that had run for 15 min and 30 min had more strength than those that did not run (p = 0.02 and 0.04, respectively).
Conclusions: Both laser therapy and running were found to hasten Achilles tendon repair In general, the rats that received higher dosages of laser energy (4 J/cm2) and ran for longer periods (30 min) performed better than those that received lower dosages of laser energy and ran for shorter periods.