MOTOR UNIT-ACTIVITY DURING HUMAN SINGLE JOINT MOVEMENTS

Citation
Sj. Garland et al., MOTOR UNIT-ACTIVITY DURING HUMAN SINGLE JOINT MOVEMENTS, Journal of neurophysiology, 76(3), 1996, pp. 1982-1990
Citations number
27
Categorie Soggetti
Neurosciences,Physiology
Journal title
ISSN journal
00223077
Volume
76
Issue
3
Year of publication
1996
Pages
1982 - 1990
Database
ISI
SICI code
0022-3077(1996)76:3<1982:MUDHSJ>2.0.ZU;2-G
Abstract
1. To explore the neural control of single joint movements in humans, the activity of 47 motor units in triceps brachii muscle was recorded during elbow flexion and extension movements. Movements were performed with different but changing deceleration magnitudes, while the accele ration magnitude was kept constant, to determine the relationship betw een motor unit activity and the acceleration and deceleration characte ristics of single joint movements. 2. The number of motor unit action potentials was found to vary with the magnitude of the movement decele ration. Ln addition, the duration of the discharge of a motor unit was found to parallel the duration of the acceleration phase of the movem ent, when the acceleration duration was varied while acceleration magn itude was kept constant. 3. Approximately half of the recorded motor u nits in triceps brachii were active both in the initiation and in the termination of the extension movements. However, motor units were iden tified that participated in specific phases of the movement (i.e., eit her during the Ist agonist or 2nd agonist burst of muscle activity) de pending on the magnitude of the acceleration or deceleration. 4. Durin g flexion movements. when the triceps muscle served as an antagonist, approximately half of the motor units were recruited only when the mag nitude of the flexion deceleration was large. Further, this decelerati on magnitude was larger than that evident during the extension movemen ts in which the motor unit discharged. 5. The findings of this study d emonstrate that the nervous system activates the same motor units whet her the muscle is functioning as an agonist or antagonist so as to con trol the characteristics of acceleration and deceleration of single jo int movements.