Effects of Low-Level Laser Therapy Applied Before Treadmill Training on Recovery of Injured Skeletal Muscle in Wistar Rats.

Abstract

The aim of this study was to analyze the effects of low-level laser therapy (LLLT) when associated with treadmill training on the recovery of skeletal muscle, during two periods of rest after muscle injury in rats. Because of photostimulation, LLLT has been presented as an alternative for accelerating the tissue healing process. Forty rats were divided into two groups (A and B) containing four subgroups each: GC (Control Group)-cryolesion untreated; EG (Exercise Group)-cryolesion treated with physical exercise; LG (Laser Group)-cryolesion treated with laser; ELG (Exercise and Laser Group)-cryolesion treated with laser and physical exercise. The right tibialis anterior (TA) of the middle belly was injured by a cooling iron bar (cryoinjury). Group A remained at rest for 3 days, whereas Group B remained at rest for 7 days. The laser parameters utilized were 780 nm with 15 mW average optical power and spot size of 0.04 cm(2) applied during 10 sec, leading to 0.152 J and 3.8 J/cm(2). Treadmill training with and without laser application was performed during 5 days, with each session lasting for 12 min at a velocity of 17 m/min. Subsequently, the TA muscle was removed for a histological and morphometric analysis. The damaged area was significantly smaller for the ELG at both periods of rest, 3 and 7 days, respectively (4.4 ± 0.42% and 3.5 ± 0.14%, p < 0.05), when compared with the LG (18.6 ± 0.64% and 7.5 ± 0.13%), the EG (21 ± 0.26% and 8.7 ± 0.32%), and the CG (23.9 ± 0.37% and 21.4 ± 0.38%). In addition, the number of blood vessels were significantly higher for the ELG at both periods of rest, 3 and 7 days, respectively (71.2 ± 13.51 and 104.5 ± 11.78, p < 0.05), when compared with the LG (60.6 ± 11.25 and 93.5 ± 16.87), the EG (51.6 ± 7.3 and 93.8 ± 15.1) and the CG (34.4 ± 2.54 and 65.7 ± 14.1). The LLLT applied before the physical exercise on the treadmill stimulated the angiogenesis and accelerated the process of muscle recovery.