The brain plays an important role in the modulation of perceived exertion and fatigue during exercise, however, little is known about the brain areas associated with those responses. According to the model of fatigue (Central Governor Model), in intense physical exercise, there is a protection mechanism of vital organs that modulates neuromuscular activity subconsciously, and consciously, the process involved reflects an increase in perceive exertion until the subject reaches in fatigued and terminate the exercise. It is suspected that this psychophysiological control in the brain might be integrated by subcorticais areas responsible for the processing of sensations and feelings. Subcorticais regions activity is possible by means of the technique of functional magnetic resonance imaging (fMRI). Recently, transcranial direct current stimulation (tDCS) has been constituted in a safe and effective non-invasive neuromodulation technique being used for treatment of diseases of neural disorders such as depression and chronic pain. Evidences point to a new field of application of the tDCS related to physical performance and fatigue whereas results obtained by our group indicated increase in physical performance and reduced perceived exertion after brain stimulation. However, the brain areas modulated by tDCS which are associated with the improvement of physical performance and reduced perceived exertion were not measured. Based on these reports, the aim of the present study is to analyze the effect of tDCS on the brain (fMRI), responses, perceived exertion and aerobic performance. To test these hypotheses, 20 male subjects, will perform: (a) an incremental cycle ergometer test to obtain the maximum load (Wmax); (b) two constant workload and exhaustive tests on intensity corresponding to the 70Wmax (1. anodal-20 minute tDCS stimulation of anodal current in the left temporal cortex before the test; 2. tDCS sham (placebo)-the subject will carry out the same procedures of anodal tDCS, however, will not receive electrical stimuli). All tests will be taken fMRI (Siemens 3T Magnetom Allegra MRI scanner), perceived exertion, heart rate and time to exhaustion. Two-way ANOVA with repeated measures will be used to compare the brain responses, the perceived exertion, heart rate and time to exhaustion, obtained in two experimental conditions (anodal or sham). The significance level adopted will be P 0.05. The use of new technologies such as the tDCS in order to modulate neural function and brain activity during dynamic exercise with fMRI will allow a better understanding of the mechanisms of fatigue and exhaustion during high intensity physical exercise.
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