Effects of tendon vibration on unimanual and bimanual movement accuracy.

Vibration-induced changes in target accuracy were examined to determine the influence of afferent information on unimanual and bimanual movements. Normal adult male subjects (N = 4) undertook a 90 degrees curvilinear positioning task (flexion and extension of the elbow) in the absence of vision. Each trial required the subject to reproduce a criterion target position while one of three vibration treatments was applied to the distal aspect of the triceps brachii tendon of the dominant arm. Vibration (100 Hz) was administered manually either prior to or concurrently with movement. Subsequent movement outcome was compared with a control or no-vibration condition. In the unimanual condition application of vibration to an antagonist muscle produced consistent undershoot of approximately 10 to 12% of the total movement amplitude. In contrast, vibration of the agonist produced minimal error in movement. A similar pattern was seen in the vibrated dominant arm of the bimanual condition; however, the results exhibited no interaction between hands. Target accuracy during prior vibration did not differ significantly from control trials and we concluded that vibration was an inappropriate stimulus to distort initial condition information. The observed results are consistent with vibration-induced activation of muscle spindle receptors in the lengthening muscle during movement. We concluded that afferent information from an antagonist muscle is critically important in the final movement outcome, but there was no evidence of contralateral effects.