Effect of Light-Emitting Diode on the Strenght and Resistence Capacities of Cycling Athletes

Phototherapy is a therapeutic resource of increasing use in the last decade. The photobiomodulatory effects are commonly produced by means of low intensity lasers or LED emitting diodes, and can be used at different wavelengths. These light sources are divergent as to coherence, but produce equivalent tissue effects. The application of laser or LED light is able to induce biochemical changes in tissues, allowing for inhibitory or stimulating effects. These responses are associated to a cascade of cellular reactions, which favor the absorption of enzymes by cytochrome c oxidase, generating physiological responses that lead to decreased production of reactive oxygen species and increased synthesis of adenosine triphosphate (ATP). The application of this therapeutic resource brings ergogenic and protective benefits in muscular performance. 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. Hypothesis: It is hypothesized that the LED application is capable of improving athletes performance in terms of increased fatigue resistance, increased strength and power, increased muscle recruitment, and optimized oxygen demand. It is also expected that the results generated in this study can contribute to and increase the resources used by physiotherapists within the clinical-sports field, contributing to the post-training recovery, as well as the more effective physical performance in competitive activities.

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 application of this therapeutic resource brings ergogenic and protective benefits in muscular performance. 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 48 male cyclist athletes randomly allocated into three groups: Infrared LED Group (G-I), Red LED Group (G-V), Infrared plus Red Group (G-IV) 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 (180 J) will be applied three times in three differents days 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 adopte

Eligibility Criteria:
Inclusion Criteria:

* Cycling practitioners
* Age between 18 and 45 years;
* Male
* VO2MÁX \> 40 ml.kg-1.min-1;
* Absence of musculoskeletal injury in the last six months

Exclusion Criteria:

* Carriers of Cardiorespiratory Diseases;
* Users of anti-inflammatory and analgesic drugs
* Users of Alcohol and illicit drugs