Acute effects of gastrocnemius muscle stretching after contusion in rats

The aim of this study was to evaluate the acute effects of stretching after gastrocnemius contusion in rats. Thirty-three male Wistar rats were selected (8 weeks, 219±35 g) and divided into 4 groups: Control (CG, n=3) - intact; Lesion (LG, n=10); Stretching (SG, n=10): Lesion and Stretching (LSG, n=10). The right gastrocnemius (RG) was submitted to contusion. Stretching on RG was performed manually, with 4 repetitions of 30 seconds each day, for 5 consecutive days, beginning 72 hour after contusion. One week later, rats were weighed and both paws were removed for investigation of muscle length, serial sarcomere number and sarcomere length. The final body weight increased in all groups. The muscle weight and length, as well as the serial sarcomere number (SSN) of LG, were higher than SG. However, the SSN of LSG was higher than SG. The sarcomere length of SG was the highest among all groups. It was concluded that the contusion and stretching did not affect body weight gain. The stretching induced sarcomerogenesis in injured muscle, but did not modify the healthy muscle.