INTRODUCTION: Studies have demonstrated the effectiveness of the infrared laser (IR) on the skelet al muscle activity. However, it was not found studies on the effects of radiation emitted by IR LED (Light Emitting Diode) on the activity of masseter muscle (MM, important muscle of mastication), the aim of the present study. METHODS: Ten volunteers were involved and their electromyography (muscle activity, strength and fatigue time) and blood lactate levels (mmol/L) were analyzed after placebo, laser (GaAlAs, 780 nm) and LED (GaAlAs, 880 nm) therapies. The signals obtained previously conducted before the therapies were taken as control. The irradiation parameters (laser or LED) were: output power of 0.02 W, energy density of 4 J/cm² and beam area of 0.2 cm². Eight points on the MM were irradiated in a perpendicular and transcutaneous form with a 1-cm distance between the points. RESULTS: Muscle activity was significantly higher after laser and LED therapies when compared to control. No significant differences were found in force, fatigue time and blood lactate levels after placebo therapy, laser or LED, when compared to control. CONCLUSION: The results suggest the optimization of muscle activity with the use of laser or LED therapy, without causing side effects such as the increase in the force and levels of lactate.
Masseter muscle activity; Muscle fatigue; Muscle force; Lactate; Laser; LED
