Abstract
The fatigue is a very complex physiologic phenomenon that might be defined as a fail in keeping the muscular strength and maintain its working in a defined intensity of exercise or the induced reduction by the exercise itself in the capability of exerting strength or muscular potency. The important functional limitations defined by the fatigue that appears both in pathologic and physiologic conditions, as well at the athletic or occupational sphere, make it a very relevant scientific investigation subject. Historically, have been defined two manifestation ways of fatigue; the "peripheral fatigue", described by skeletal muscular dysfunction as consequence of insufficient oxygen and energy substrates supply by the cardiovascular system, and from the high amount of metabolites that prejudices the muscular activity; and the "central fatigue" defined by a failure at the voluntary neural activation and recruitment of the skeletal muscular fibers. This way, for the fatigue's research, is necessary an integrative approach of the interactions among the skeletal muscles and its motor central control. The inclusion of the nervous central system at the fatigue's research allow the consideration as tough not exclusive of non-neural activities motor, but subjacent to phenomena as the sensorial perception, emotional regulation, motivation and a decision-making, that are also very important for the fatigue's determinants and the decrease of the performance during the physical exercise. So, the brain would have a crucial function at the fatigue's determination, acting as a regulator of motor behavior during the physical exercise. Likewise, it is proposed that the brain uses the fatigue symptoms, what means, the unpleasant sensations associated with physiological alterations that occur in the body during the physical exercise, to make a complex neural/mental processing and elaborate motor programs which are suitable and continuously adjusted to organism physiological ability. New researches are indicating certain brain structures that could be involved in this process. The insular cortex, located in the lateral sulcus of the cerebral hemisphere, has proved itself a relevant structure since its activation has been linked with the decreasing or ending of the physical activity, possibly for exerting inhibitory influence on the motor cortex. According to its nociceptive, thermal, proprioceptive and visceral afferents, the insular cortex is able to integrate important information for enforcement of sensory, perceptual, emotional and cognitive process concerning the body's state and homeostatic regulation. Accordingly, the insular cortex could mediate the integration of the information related to the physiological changes that occurs during the exercise and modulating the fatigue's perception. In this scenario, based on concept of fatigue as an emotion generated by the physiological changes that occur in the body during exercise performance, and the perceived exertion as the feeling of these changes; and considering the cortex insular as a brain structure associated with neural activities subjacent to sensory and emotional processes important to homeostasis regulation, this project's purpose is investigating the involvement of this structure in determination of the exhaustion during a physical performance test in rats. (AU)
|