Voluntary contraction is widely accepted as being under continuous reflex control by a variety of sensory receptors, including those in both agonists and antagonists. The questions arise as to how the spinal reflex adjustments may be modified by the application of vibration to antagonist muscles and how this may induce psychophysical errors in the attainment of intended final position. Recent psychophysical investigations have suggested that in man, the central nervous system (CNS) may concomitantly process all the information conveyed by a pair of antagonist muscles moving the same joint. Therefore, the present study was undertaken to examine effects of muscle vibration on distortion of kinesthetic sensasion. Particularly, aftereffects (influences after the vibration was stopped) was investigated. For this purpose, the muscle vibration was applied during the repetitive elbow extention-flextion in nomal human subjects. The vibration was applied over the biceps brachii muscle. After a period of practice, subjects were assigned the target movements required at non-visually guided (eye closed). Thus, after-effects of vibration produced an overshoot of the extension target that was dependent on intensity of vibration. However, after-effects of vibration disappeared after the several trials. Taken together present results and previous reports, it was suggested that distortion of kinesthetic sensation after the vibration occurred from discharge of muscle spindles and length of the post-vibrationed muscle was perceived as shorter than it really was, but it was modified by the CNS after motor learning
