TY - JOUR
T1 - Human motor-unit recruitment during isometric contractions and repeated dynamic movements
AU - Thomas, C. K.
AU - Ross, B. H.
AU - Calancie, B.
PY - 1987/1/1
Y1 - 1987/1/1
N2 - 1. Spike-triggered averaging was used to determine the twitch tensions and contraction times of motor units in the abductor pollicis brevis muscle of two human subjects for two directions of isometric contraction: abduction and opposition of the thumb. 2. During isometric contractions in each direction, the threshold force for motor-unit recruitment and the twitch amplitude were correlated linearly. These data suggested that an orderly pattern of recruitment, according to increasing twitch size, described the function of the human abductor pollicis brevis muscle for each contraction direction. 3. Rank order of motor-unit recruitment in each isometric contraction direction was correlated, but not identical. All units contributed tension in each direction of contraction, so no clear evidence was found for task-dependent motor units. 4. In two subjects, motor-unit recruitment order during isometric contraction of the first dorsal interosseous and abductor pollicis brevis muscles was then compared with that of motor-unit pairs in both muscles during repetitive dynamic movements. Recruitment according to increasing twitch size was largely preserved during the repetitive opening and closing of scissors. The recruitment reversals that were observed were usually between pairs of units with similar thresholds.
AB - 1. Spike-triggered averaging was used to determine the twitch tensions and contraction times of motor units in the abductor pollicis brevis muscle of two human subjects for two directions of isometric contraction: abduction and opposition of the thumb. 2. During isometric contractions in each direction, the threshold force for motor-unit recruitment and the twitch amplitude were correlated linearly. These data suggested that an orderly pattern of recruitment, according to increasing twitch size, described the function of the human abductor pollicis brevis muscle for each contraction direction. 3. Rank order of motor-unit recruitment in each isometric contraction direction was correlated, but not identical. All units contributed tension in each direction of contraction, so no clear evidence was found for task-dependent motor units. 4. In two subjects, motor-unit recruitment order during isometric contraction of the first dorsal interosseous and abductor pollicis brevis muscles was then compared with that of motor-unit pairs in both muscles during repetitive dynamic movements. Recruitment according to increasing twitch size was largely preserved during the repetitive opening and closing of scissors. The recruitment reversals that were observed were usually between pairs of units with similar thresholds.
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U2 - 10.1152/jn.1987.57.1.311
DO - 10.1152/jn.1987.57.1.311
M3 - Article
C2 - 3559678
AN - SCOPUS:0023148821
VL - 57
SP - 311
EP - 324
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
SN - 0022-3077
IS - 1
ER -