In this study, we examined the effect of motor imagery on the accuracy of motion and excitement of the spinal nerve function. The subjects were 20 healthy volunteers (10 males, 10 females; mean age, 22.6 ± 3.9 years). F waves of the left thenar eminence were recorded following stimulation of the left median nerve during supine rest. Subsequently, subjects practiced the pinch movement at 50% maximum voluntary contraction (MVC), as measured by visual feedback using a pinch force view display. The pinching operation was then performed at 50% MVC visually without feedback and the motor output of the 50% MVC was calculated to measure the accuracy of the movement. F waves were then measured using motor imagery of the pinch movement. Repeat measurements were made at 50% MVC with no visual feedback.The F wave persistence during motor imagery was significantly increased compared with that of rest. However, in the period of 50% MVC ± 5%, there was no difference between the before and after motor imagery. In conclusion, motor imagery increases the excitability of the spinal nerve function, suggesting that it does not affect the accuracy of the movement.
