Avaliação da atividade eletromiográfica do músculo trapézio em indivíduos saudáveis pré e pós irradiação com laser baixa potência: estudo cruzado, controlado, randomizado duplo cego

Abstract

Although the low level light therapy (LLLT) irradiation is indicated for a variety of musculoskeletal disorders like muscle fatigue, tissue repair and as anti-inflammatory agent, its effects on muscle activity are still poorly understood. The objective of this study was to evaluate the immediate effect of LLLT of irradiation on the nerve conduction velocity and electromyographic activity of the muscle upper trapezius (UT) in healthy subjects. Twenty healthy women (mean age 23.54  2.51) were included in this study, cross-over, controlled, randomized, double blind. Each volunteer has received two types of treatment with continuous LLLT (LLLT) and the other one with LLLT placebo (LLLTP). The treatment order was randomized by raffle, being included an interval of 7 days between each laser intervention (wash-out) to prevent residual effects. The surface electromyography (EMG) was used to verify the nerve conduction velocity (CV) and muscle activity UT during shoulder elevation in isometric contraction to 5 different levels of contraction (10, 15, 20, 25, 30% of maximum voluntary contraction), via visual feedback provided through a driving line. The collects of the EMG signal were performed before and after 30 minutes of treatment (LLLT or LLLTP). In the analysis of variance for repeated measures (ANOVA) it was possible to observe a significant decrease in the amplitude of the EMG signal to treatment with LLLT (p = 0.0001) but not to the placebo treated group (p < 0.05). Regarding of the CV, no change was observed for both treatments (LLLT: p > 0.05; LLLTP: p > 0.05 - ANOVA). In this study it could be observed an immediate effect of LLLT irradiation on the amplitude of the electromyographic signal of the trapezius muscle descending fibers in healthy individuals, but not on the nerve conduction velocity.