Continuous therapeutic ultrasound accelerates repair of contraction-induced skeletal muscle damage in rats.

OBJECTIVE To examine the effect of ultrasonography on the repair of muscle injured through repeated eccentric contractions. DESIGN Randomized, case-control study. SETTING Laboratory animal facility. ANIMALS Thirty-three Sprague-Dawley rats. INTERVENTIONS Specimens were anesthetized and each foot strapped, in turn, onto a motorized foot pedal, which moved the ankle repeatedly through a range of 110 degrees. Extensor digitorum longus muscles were injured by stimulating the peroneal nerve during foot plantarflexion. Continuous 1.0MHz ultrasound treatments at 0.5W/cm(2) were applied through water submersion technique to 1 limb daily for 3, 5, or 7 days postinjury. The contralateral limb served as an injured control. MAIN OUTCOME MEASURES Extensor digitorum longus maximum isometric tetanic force (P(o)) was measured in vitro from all extensor digitorum longus muscles and used as a functional index of muscle injury. RESULTS Analysis of variance and Tukey post hoc analysis showed no significant differences in P(o) between treated and untreated limbs at 3 and 5 days, but at 7 days postinjury, P(o) of ultrasound-treated muscle was significantly higher than was untreated muscle. CONCLUSION Seven days of continuous therapeutic ultrasound improved force production after contraction-induced muscle injury.