Motor Control of the Forearm Muscles during Catching of a Falling Ball

• Published in: Rihabiritēshon igaku Vol. 34; no. 3; pp. 218 - 225
• Main Author: HASE, Kimitaka
• Format: Journal Article
• Language: English
• Published: The Japanese Association of Rehabilitation Medicine 1997
• Subjects: electromyography; H-reflex; hemiplegia; motor control
• ISSN: 0034-351X; 1880-778X
• DOI: 10.2490/jjrm1963.34.218

The muscle activity patterns of flexor and extensor carpi radialis (FCR and ECR) associated with catching a falling ball were investigated by surface EMG recording and was compared with the FCR H-reflex changes. Fifty-five normal upper limbs (35 men; mean age, 46.5 y/o) and 10 spastic upper limbs (10 hemiparetic men; mean age, 54.0 y/o) were studied. The subjects, sitting in a confortable chair with their forearm on the chair's rest, were asked to catch and hold a ball (700g, 65mm in diameter) dropped from 25cm. The ball took 241.2±6.3 (mean±1 SD) msec to reach the palm. An early EMG burst in FCR with a latency of 141.5±18.0 msec and a duration of 50-100 msec was detected in every catch of all normal limbs; this was considered the perceptional response. On the other hand, the weak EMG activity noted in ECR before dropping the ball was thought to be a tonic response in anticipation of the ball's impact. The FCR H-reflexes were inhibited at the drop starting point and were gradually facilitated until the perceptional response. These H-reflex changes were closely related with the background EMG activities in FCR and ECR under reciprocating inhibitory mechanisms. Anticipating the ball's impact, the cocontraction to build up resistance of the wrist joint to vertical displacement was shown after the perceptional response and the FCR H-reflex at 200 msec from the drop starting point was facilitated remarkably. Three spastic hemiparetic patients, who could not individually move their affected side fingers, had no perceptional response during catching and FCR H-reflex sizes were unchanged even iust before impact. But the perceptional response was detected occasionally with repetition of the catching task. Other patients except one who could move their individual fingers were similar to normal subjects. A mild left hemiparetic patient with hemineglect had no perceptional response but a normal FCR H-reflex pattern.