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Motor unit activation order during electrically evoked contractions of paralyzed or partially paralyzed muscles
Author(s) -
Thomas Christine K.,
Nelson Gary,
Than Lara,
Zijdewind Inge
Publication year - 2002
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/mus.10111
Subject(s) - motor unit , anatomy , electromyography , spinal cord , medicine , spinal cord injury , chemistry , anesthesia , physical medicine and rehabilitation , psychiatry
The activation order of motor units during electrically evoked contractions of paralyzed or partially paralyzed thenar muscles was determined in seven subjects with chronic cervical spinal cord injury. The median nerve was stimulated percutaneously with pulses of graded intensity to produce increments in the compound electromyogram (EMG) and force. Each increment corresponded to the activation of another unit. The evoked unit EMG and force was obtained by digital subtraction. The thenar muscles had between 15 and 83 units (26 ± 19) that produced 114.3 ± 127.1 mN force ( n = 290). In six subjects, a significant positive correlation was found between activation order and unit force indicating that weaker units were excited before stronger units. These data are contrary to the notion that a reversal of unit activation order occurs during evoked versus voluntary contractions. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002