Muscle fatigue is caused by biochemical changes that modify the mechanics of muscle contraction, resulting in negative changes in the performance of the contraction. Several resources are studied in order to mitigate this situation, among them we can mention Low Level Laser Therapy (LLLT). The objective is to evaluate the effects of LLLT on brachial biceps muscle fatigue in healthy individuals and individuals with spastic hemiparesis. A double-blind, comparative, randomized, double-blind, double-blind clinical trial will be conducted. Phase I will be composed of 30 healthy individuals and Phase II will be composed of 30 post-stroke individuals. The study will consist of three groups (Control Group, Placebo Group and LLLT Group) and all individuals will go through all groups, following the criteria of randomization. The protocol consists of the LLLT application in the brachial biceps muscle of the dominant side in healthy individuals and in the hemiparetic side of the post-stroke individuals, previously performing the Maximum Voluntary Isometric Contraction (MVIC) for 50 seconds in the dynamometer. The pain intensity will be evaluated through the Visual Analog Pain Scale, the myoelectric activity through the surface electromyography associated with the evaluation of muscle torque through the dynamometer. The local temperature will be evaluated by means of red-blood thermography and blood lactate concentration by means of the lactimeter, which will be measured at four different times, prior to the application of the laser (basal) and 3, 15 and 25 minutes after MVIC. LLLT is believed to minimize pain intensity, increase RMS values and time onset of muscle fatigue.
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