Physical fatigue refers to a progressive decline in the ability to activate muscles voluntarily. Although the existence of central inhibition of the motor area via visual feedback during physical fatigue was noted in our previous behavioral study, neural evidence has not been presented. In addition, although the neural mechanisms of central inhibition of the motor area during physical fatigue have been widely investigated, mechanisms supporting motor output during fatigue remain to be clarified. The central mechanism to regulate physical fatigue was systematically examined using a magnetoencephalographic (MEG) system. The study group consisted of eleven healthy participants. They were randomly assigned to two groups in a crossover fashion to perform fatigue-inducing physical task sessions, in which they performed repetitive grips of a dominant hand at maximal voluntary contraction levels every second without using Ramachandran’s mirror box to see the dominant hand or with using the mirror box to see the mirror reflection of the dominant hand to perceive that the fatigued dominant hand was not fatigued non-dominant hand. Before and after each session, imagery of maximum grips of the dominant hand was performed for the evaluation with MEG. Beta-band event-related desynchonization (ERD) level of motor movement-evoked magnetic field in the contralateral sensorimotor area was reduced after the fatigue-inducing session without the mirror box, although it was not altered after the session with the mirror box. In addition, the ERD levels of the motor movement-evoked magnetic fields in the prefrontal and ipsilateral sensorimotor areas were increased after the session. We identified neural evidence of the central inhibition and showed that the visual feedback system is involved in the central mechanism regulating motor output. In addition, the ipsilateral sensorimotor and prefrontal areas are brain regions associated with compensation mechanisms to support motor output under the condition of physical fatigue.

DESCENTE SPORTS SCIENCE Vol.33/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE