Morphologic study of different treatments for gastrocnemius muscle contusion in rats☆

OBJECTIVE Evaluate the effects of ultrasound and stretching in morphology after rat muscle contusion. METHODS Male Wistar rats (n = 35, 8-9 weeks, 271 ± 14 g) were divided into five groups: control group (CG = 3); lesion group (LG = 8); lesion + ultrasound group (LUG = 8); lesion + stretching group (LSG = 8); lesion + ultrasound + stretching group (LUSG = 8). The ultrasound was applied in LUG and LUSG from the third to the seventh day, the dose used was 50% pulsed, 0.5 W/cm2, 5 min. From the tenth until the twenty first day, passive stretching was performed, in four repetitions lasting 30 s each with 30 s of rest. Initial and final body weight, muscle weight and length, number and sarcomere length, muscle fiber cross-sectional area, and percentage of collagen were evaluated after 22 days. RESULTS The final body weight was higher than the initial in all groups. The number of sarcomeres was statistically higher in LSG than LUG and higher in LUSG than LUS and CG; in sarcomere length was higher in LUG when compared with LSG (p < 0.05). The cross sectional area in LG was higher than LSG, and the percentage of collagen was higher in LG when compared with LSG and CG; in LUG when compared with LSG and CG; and in LUSG when compared with CG. CONCLUSION The passive stretching protocol induced sarcomerogenesis and antifibrotic effect over the muscle submitted to contusion. Ultrasound, even in association with stretching, was not sufficient to prevent fibrosis in the injured muscle.