INFLUENCE OF THERAPEUTIC ULTRASOUND ON SKELETAL MUSCLE REGENERATION FOLLOWING BLUNT CONTUSION

Abstract

INTRODUCTION Following skeletal muscle contusion injury, therapeutic ultrasound is one of the most commonly used treatment modalities among athletic trainers and other sports medicine practitioners. Pulsed ultrasound is characterized by a non-thermal, mechanical stimulation and over the course of several days this environment purportedly hastens the regenerative skeletal muscle healing process. However, the structural outcomes underlying this potential effect are not well understood. PURPOSE Our working hypothesis was that following a blunt contusion injury to the gastrocnemius (GTN) muscle, ultrasound treatment would facilitate the recovery of several biological markers of the skeletal muscle regenerative repair process. METHODS Eighty male Wistar rats (three-mo) were studied. Following anesthetic administration, each animal received a bilateral contusion injury to the GTN muscle. Pulsed ultrasound treatment was subsequently initiated six hours post-contusion injury unilaterally on the right (R) GTN muscle, and ultrasound treatment was continued once daily for seven days. The left (L) (non-ultrasound treated) and R (ultrasound treated) GTN muscles of 10 animals per group were excised at 1−, 3−, 5−, 7−, 14−, 21−, 28−, and 40− days post-contusion injury. RESULTS There were no differences in muscle mass, total protein concentration, or fiber cross-sectional area (CSAf) between the R and L GTN muscles at any post-injury time point examined. Further, when CSAf was normalized to muscle mass, there were no differences. Myonuclear number and CSAf per myonuclei between the R GTN muscles and the L GTN muscles were not different. CONCLUSION The hypotheses were not supported and the results suggest that pulsed therapeutic ultrasound treatment as administered is not effective in hastening the regeneration of the markers of skeletal muscle regeneration examined following a contusion injury.