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Motor unit recruitment and discharge behavior in movements and isometric contractions
Author(s) -
Ivanova T.,
Garland S.J.,
Miller K.J.
Publication year - 1997
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/(sici)1097-4598(199707)20:7<867::aid-mus11>3.0.co;2-p
Subject(s) - isometric exercise , motor unit , electromyography , kinematics , physical medicine and rehabilitation , motor unit recruitment , contraction (grammar) , medicine , anatomy , physics , physical therapy , classical mechanics
The purpose of this study was to contrast the discharge patterns of the same motor units during movements and during isometric contractions that were produced with comparable torque‐time characteristics. Subjects performed elbow flexion and extension movements with predetermined acceleration characteristics. The average acceleration and deceleration profiles for the movements were reproduced in the isometric setting by presenting the kinematic profiles as templates for torque production. Trained subjects were able to match the first agonist (AG1) and antagonist (ANT) electromyographic (EMG) bursts, but tended to produce a smaller second agonist burst (AG2) in the isometric contraction. Twenty‐five motor units from triceps brachii were studied. The same motor units (with one exception) were recruited and subsequently discharged in a similar fashion in both the isometric and movement tasks in the AG1 and ANT EMG bursts, with fewer motor unit discharges in the AG2 burst in the isometric contraction. The central control mechanisms appear to be the same for the acceleration phase of movement and isometric contraction, but differ during the deceleration phase. © 1997 John Wiley & Sons, Inc. Muscle Nerve 20: 867–874, 1997.