Irradiation with LEDT (100 LEDs with wavelength 630 nm, spot size 2.5 , power density 0.048 , and energy density 57.6 ) was performed in non-contact mode with the probe held stationary at a vertical distance of 60 mm between light source and skin surface. The total time of therapy was 20 minutes. Opaque goggles were used for all participants during the therapy to protect their eyes from the treatment and assure the blindness of the study.

630 nm, 0.048 power density, 57.6 energy density, 20 minutes

https://www.hindawi.com/journals/ijp/2012/652040/

This paper aims to investigate the effect of light emitting diode therapy (LEDT) on exercise-induced hand muscle fatigue by measuring the surface electromyography (sEMG) of flexor digitorum superficialis. Ten healthy volunteers were randomly placed in the equal sized LEDT group and control group. All subjects performed a sustained fatiguing isometric contraction with the combination of four fingertips except thumb at 30% of maximal voluntary contraction (MVC) until exhaustion. The active LEDT or an identical passive rest therapy was then applied to flexor digitorum superficialis. Each subject was required to perform a re-fatigue task immediately after therapy which was the same as the pre-fatigue task. Average rectified value (ARV) and fractal dimension (FD) of sEMG were calculated. ARV and FD were significantly different between active LEDT and passive rest groups at 20%–50%, 70%–80%, and 100% of normalized contraction time (). Compared to passive rest, active LEDT induced significantly smaller increase in ARV values and decrease in FD values, which shows that LEDT is effective on the recovery of muscle fatigue. Our preliminary results also suggest that ARV and FD are potential replacements of biochemical markers to assess the effects of LEDT on muscle fatigue.