Effect of Low-Power Gallium–Aluminum–Arsenium Noncoherent Light (640 nm) on Muscle Activity: A Clinical Study

Background Data: Studies have shown the significant effects of electromagnetic irradiation in the visible region, with laser as an irradiation source. However, the effect of LEDs (light-emitting diodes) irradiation in similar wavelengths is not known. Objective: The purpose of this clinical study was to verify the effects of the LED (640 nm with 40 nm full bandwidth at half maximum) on muscle activity. Methods: The study was done with 30 test subjects, of both genders, aged 23 ± 3 years, with a mean weight of 60 kg, divided into three groups ( n = 10). Fatigue was induced through the maximum power of a bite, for 60 s in two overlaid occlusal platforms, coupled to a load cell and to a biologic signal-acquisition device. LED irradiation of the right masseter muscle was applied to all subjects. The left muscle received placebo treatment. Irradiation was applied in eight points on the right masseter muscle (transcutaneous), 1.044 J per point, 2.088 J per point, or 3.132 J per point, 0.116 W, 0.522 cm 2 spot size, 0.816 cm spot Ø, continuous wave, perpendicular to the skin. Results: An increase in muscle activity was observed after irradiation with 1.044 J per point ( p