This study examined the extent to which motor imagery can facilitate to specific pools of motoneurons. Motor commands induced by motor imagery were sub-threshold for muscle activity and were presumably not associated with any change in background afferent activity. To estimate excitability changes of flexor carpi radialis (FCR) muscle motoneuron in spinal and cortical level, electric stimuli for recording H-reflex and transcranial magnetic stimulation (TMS) for recording motor evoked potentials (MEPs) were used. During motor imagery of wrist flexion, re-markable increases in the amplitude of the MEP of FCR were observed with no change in the H-reflex. Furthermore, facilitation of antagonist (extensor carpi radialis ; ECR) was also observed. Therefore, it is concluded that internal motor command can active precisely cortical excitability with no change in spinal level without recourse to afferent feedback.

DESCENTE SPORTS SCIENCE Vol.18/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE