Background: Phototherapy is a therapeutic resource of increasing use in the last decade. The photobiomodulatory effects are produced by sources of low-level lasers or light- emitting diode (LEDT), and their tissue effects are equivalent. The use of LED as a light source is promising because of its low cost, but there are no enough studies that support this use in athletes, with a focus on performance improvement. In addition to the deficiency of the sample, there is also no consensus regarding the use of different wavelengths for LED in the literature, thus opening gaps for the best protocol for the application of this technique. Therefore, a study that evaluates the use of LED in athletes, with different wavelengths, to improve performance is necessary. Objective: To analyze the acute effects of the application of LED phototherapy on the strength and fatigue strength abilities of cycling athletes. Method: The study sample will be composed of 36 male cyclist athletes randomly allocated into three groups: Infrared LED Group (G-I), Red LED Group (G-V) and Sham Group (G-S). The athletes will be submitted to a battery of tests, for performance evaluation which consist of anaerobic and aerobic power and threshold, bioimpedance, infrared thermography, creatine kinase (CK) and blood lactate analysis, measurement of local muscle blood flow, gas analysis, besides the isokinetic, electromyographic and biomechanical evaluations. After 24 hours of the tests, the LEDT (30 J) will be applied to the quadriceps femoris muscle bilaterally. The same tests will be performed 24 hours after the application of LEDT. In the 1st and 4th week, post intervention, only the isokinetic and electromyographic evaluations will be performed. For analysis of the data, normality test will be used to verify the distribution and adequate statistical tests for the appropriate intra and intergroup comparisons, being considered two factors in the comparisons, time and group. A significance level of 5% will be adopted.
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