Effects of Low-level Laser Therapy in the Fatigue Muscle of Healthy Individual and Spastic Individuals

Muscle fatigue is caused by biochemical changes that modify the mechanics of muscle contraction, which result in negative changes in the performance of the contraction. Several resources are studied in order to mitigate this situation, among them we can mention the Low Level‐Laser Therapy (LLLT), which has demonstrated positive effects in the treatment of muscle disorders and fatigue prevention. The effects of LLLT are being studied in healthy individuals with fibromyalgia and athletes, currently studies are being performed on spastic muscles with post‐stroke patients (post‐stroke). The objective of this study is to evaluate the effects of LLLT on brachial biceps muscle fatigue in healthy individuals and individuals with spastic hemiparesis. A double‐blind, cross‐sectional, comparative, randomized, double‐blind clinical trial will be conducted. Phase I will consist 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 LLLT application in the dominant side brachialis muscle in healthy subjects and on the hemiparetic side of post‐stroke individuals, prior to performing the Isometric Maximum Voluntary Contraction (IMVC) for 50 seconds in the isokinetic 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 the muscular torque through the isokinetic dynamometer. The local temperature will be evaluated by infrared 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 collection) and 3, 15 and 25 minutes after IMVC.