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.