Effects of vibration applied on forearm and upper limb muscles on human voluntary multi-wrist and elbow movements

Abstract

The effect of forearm and upper limb muscles vibration during extension and flexion movement of wrist and elbow was studied in 10 normal human subjects. In first experiment, a vibratory stimulation was applied to either the flexor carpi ulnaris (FCU) or the biceps brachii (BB) muscle during simple and simultaneous extension movement about wrist and elbow. In second experiment, vibratory stimulation was applied to either the extensor carpi radialis (ECR) or the triceps brachii (TB) muscle during simple and simultaneous flexion movement about wrist and elbow. The main new findings of the present study are as follows. During simple and simultaneous extension-flexion movements of the elbow, the application of vibration to the FCU or to the ECR produced an undershoot of the target position. However, no undershoot was observed by the application of vibration to the BB or the TB during simultaneous extension-flexion movements of the wrist. From these results, it was revealed that although there are cases where the phenomenon of undershoot resulting from vibration of the wrist and elbow during simple and simultaneous movements corresponds to the type of synaptic connection from muscle spindle group Ia sensory inputs to alpha motor neurons, as identified by Cavallari & Katz (1989) and Cavallari et al. (1992), the manifestation of undershoot is influenced by differences between the movement patterns of the wrist and elbow joints, as well as the differences between simple movement and simultaneous movement.