A motor program for controlling one’s own movement requires sensory signals from the target body parts. Information for movement is provided by sensory feedback such as visual and somatosensory information. Previous studies indicated that cortical activity related to sensory response and perception is modified by movement executing mechanisms. The integration of sensory information and motor command is critical for motor control and recognition of one movement. However, this raises the issue of how central nervous system integrates motor command and sensory information whenever the intended movement is in progress. Preceding and during voluntary movement, the efference copy in relation to motor signal from motor related areas modified the information processing in somatosensory areas. This review introduces the research topics of sensorimotor integration and new findings according to recent studies of the somatosensory system in relation to sports science.

The somatosensory evoked potential (SEP) is attenuated (gating) and the spinal motoneuron pool is facilitated before and during movement. However, the relationship between these changes has not been elucidated. In the present study, the SEP and the evoked electromyogram were simultaneously recorded during a discriminative reaction task in seven healthy subjects. Electrical stimulation applied to the posterior tibial nerve in the popliteal fossa was used as a response signal. The experimental condition were: 1) full relaxation and no response to either right or left stimulation (Control) ; 2) no response to right stimulation and quick contraction of right ankle with left stimulation (L-R) ; 3) no response to left stimulation and quick contraction of right ankle with right stimulation (R-R) . Right and left legs were randomly stimulated under each condition. The H-response gains of the right leg with movement were significantly facilitated compared to the left leg without movement in L-R and R-R conditions. The results indicated that movement enhanced the motoneuron excitability regardless of sensory concentration. In the L-R condition, N 40 at Cz evoked by left operative stimulation that produced right leg movement was significantly increased. However, in the R-R condition, it was significantly attenuated when it was recorded by right operative stimulation that produced right leg movement. These results indicated that concentration on the operative stimulation enhanced the N 40 gain and it reflected the concentration on sensory information, but simultaneously induced the movement, and its gain was strongly controlled by the motor system.

The mechanism of the latent reaction time in task completion in elderly men was investigated by comparing the reaction time (RT), EMG-RT and motor time (MT) in young and elderly men. The motor performance was recorded as task completion through as a WS-RS, simple reaction or a choice reaction for each movement using a handgrip and switch.
In this study, we found that the RT and EMG-RT of elderly men in all movements of WS-RS and choice reaction tasks were significantly longer than those of young men, especially in the choice reaction tasks were striking. Moreover, the MT of elderly men in all tasks was significantly longer than those of young men.
These findings suggest that the latent RT and EMG-RT in a choice reaction task may be due to relayed information processing through as the discrimination and cognition functions in the brain, and that it may be also influenced by the mechanism of the latent reaction time of task completion in elderly men.

We studied whether exercise fatigue affects somatosensorv input using somatosensory evoked potential (SEP) . Sixteen subjects performed intermittent grip strength exercises with muscle fatigue while ignoring electrical stimulation given to an elbow. We induced SEP in the exercise task (during contraction) in every stage (first stage, middle stage and final stage) . In addition, we induced SEP in the exercise task during relaxation in the first stage and final stage. As a result, the early component amplitude of SEP decreased with the progress of exercise (manifestation of muscle fatigue) during contraction and relaxation. Our findings suggested that somatosensory input decreased with the manifestation of muscle fatigue. Somatosensory input is necessary for control of voluntary movement. Therefore, we speculate that these factors play a role in decreased performance of athletes competing in long-duration events.