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 < 0.05). A significant increase (p < 0.01) in the time before fatigue was observed in the irradiated muscle with 2.088 J per point, without a change in the force of contraction (p > 0.05). This change was not observed with 1.044 J per point and 3.132 J per point. The results suggest a dose-dependent relation with this kind of noncoherent irradiation in the red region of the electromagnetic spectrum in the muscle-fatigue process. CONCLUSION: It was concluded that LED can be used as a clinical tool to increase muscle activity (1.044 J per point) and to prevent fatigue (2.088 J per point), without change in the muscle force.

Análise eletromiográfica do músculo masseter após indução de fadiga com aplicação de laser de baixa potência – resultados preliminares / Eletromyografic analysis of masseter muscle after inducion of fatigue with low power laser aplication

Diversos estudos em animais têm demonstrado a efetividade dos lasers de baixa potência (LBP) sobre a otimização da atividade muscular esquelética. Contudo, poucos estudos foram direcionados à prevenção de fadiga em humanos. Assim, o presente estudo teve por objetivo analisar a aplicação do LBP na prevenção de fadiga muscular induzida em músculo masseter (MM). Participaram do estudo 10 voluntários divididos em dois grupos: irradiados com laser em 685nm (n=5) e irradiados com laser em 830nm (n=5). Foram colhidos sinais eletromiográficos durante o processo de fadiga induzida (60 s), antes e após o tratamento. O laser foi aplicado no MM direito, utilizando-se: 30 mW, 4 J/cm², 0,0028 cm², em 8 pontos (recobrindo todo o MM, com 1 cm de distância entre os pontos). As medidas pré-irradiação foram consideradas controle. Avaliou-se a atividade muscular, tempo de fadiga, força máxima e média e, em todos esses parâmetros estudados, verificou-se a ausência de diferença significativa. Embora o laser seja indicado pela literatura, nesse presente estudo concluímos que tal tratamento não se apresentou efetivo para prevenção de fadiga muscular no músculo masseter, não devendo, portanto, ser utilizado para este fim.

Several studies in animals have demonstrated the effectiveness of low power lasers (LBP) on the optimizationof skeletal muscle activity. However, few studies have been directed at the prevention of fatigue in humans.Therefore, the objective of this study was to analyze the implementation of LBP in the prevention of muscle fatigue induced at the masseter (MM). The participants of this study were 10 volunteers divided into two groups: irradiated with laser at 685 nm (n = 5) and irradiated with laser at 830 nm (n = 5). Electromyography signals were collected during fatigue induced process (60 s) before and after the treatment. The laser was applied in the right MM using: 30 mW, 4 J / cm ², 0.0028 cm ², 8 points (covering the whole MM, with 1 cm of distance between points). The pre-irradiation measures were considered as control measures. It was evaluated the muscle activity, duration of fatigue, maximum and average power and, in all these studied parameters, there was no signifi cant difference. Although laser is indicated by literature, in this present study it was concluded that such treatment was not effective in the prevention of muscle fatigue at the masseter and, therefore, it should not be utilized to this end.

Análise eletromiografica do exercício agachamento com utilização do cinto pélvico / Electromyographic analysis of the bending down exercise using the pelvic belt

O objetivo deste estudo foi analisar eletromigraficamente os músculos: reto femoral (RF), bíceps femoral (cabeça longa) (BFCL), eretor da espinha (ES) e glúteo máximo (GM), de ambos os lados nas fases excêntrica e concêntrica durante a execução do exercício agachamento, que podem ser realizadas com ou sem a utilização de um cinto pélvico. Participaram deste estudo dez (10) voluntárias praticantes do agachamento, com idade de 20 a 22 anos, e de antropometria semelhante e sem antecedentes de lesões músculo esqueléticas. Com os resultados obtidos, concluiu-se que: o uso do cinto não apresenta um efeito significativo sobre as ações dos músculos RF, BFCL, ES e GM músculos, este fato ocorrendo apenas para o músculo glúteo máximo direito, que apresentou um maior nível de atividade, sem o uso do cinto. Todos os músculos apresentam maior atividade na fase concêntrica do movimento.

This study examined the electromyographic muscles: rectus femoris (RF), biceps femoris (long head)(BFCL), erectors spinae (ES) and gluteus maximus (GM), on both sides during eccentric and concentric during execution the squat exercise, which can be taken with or without the use of a belt pelvic. Participial this study (10) voluntary practitioner’s squat, aged 20 to 22 years, and similar anthropometry and without a history of skeletal muscle injury. With the results obtained, it was concluded that: the use of the belt does not present a signifi cant effect on the actions of the RF, BFCL, ES and GM muscles, this fact occurring only for the right gluteus maximus muscle which presented a greater level of activity without the use of the belt. Regarding the movement phases, all of the muscles presented greater levels of activity while raising the load.