Neural correlates of motor vigour and motor urgency during exercise.

This article reviews the brain structures and neural circuitry underlying the motor system as it pertains to endurance exercise. Some obvious phenomena that occur during endurance racing events that need to be explained neurophysiologically are variable pacing strategies, the end spurt, motivation and the rating of perceived exertion. Understanding the above phenomena physiologically is problematic due to the sheer complexity of obtaining real-time brain measurements during exercise. In those rare instances where brain measurements have been made during exercise, the measurements have usually been limited to the sensory and motor cortices; or the exercise itself was limited to small muscle groups. Without discounting the crucial importance of the primary motor cortex in the execution of voluntary movement, it is surprising that very few exercise studies pay any attention to the complex and dynamic organization of motor action in relation to the subcortical nuclei, given that they are essential for the execution of normal movement patterns. In addition, the findings from laboratory-based exercise performance trials are hampered by the absence of objective measures of the motivational state of subjects. In this review we propose that some of the above phenomena may be explained by distinguishing between voluntary, vigorous and urgent motor behaviours during exercise, given that different CNS structures and neurotransmitters are involved in the execution of these different motor behaviours.