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Motor unit action potential components and physiologic duration
Author(s) -
Dumitru Daniel,
King John C.,
Rogers William E.
Publication year - 1999
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(199906)22:6<733::aid-mus10>3.0.co;2-6
Subject(s) - motor unit , biceps , motor unit recruitment , duration (music) , compound muscle action potential , electrophysiology , electromyography , anatomy , biomedical engineering , neuroscience , physics , medicine , biology , acoustics
Motor unit action potentials (MUAPs) recorded from the same motor unit at two distances along the biceps brachii muscle with monopolar needle electrodes at high amplifier gains (20 μV/division) and averaged 2000–3000 times reveal total potential durations of 39.6 ± 4.6 ms. In addition, the terminal segment for each of these two MUAPs contained a late far‐field potential with a mean duration of 23.8 ± 4.1 ms. Computer simulations of MUAPs suggest that this long‐duration positive far‐field mirrors the true morphology of the intracellular action potential (IAP), which is monophasic positive, possessing a terminal repolarization phase approaching 30 ms. This investigation suggests that the MUAP's physiologic duration is directly proportional to the muscle fiber length and the IAP's duration, which becomes manifest as a positive far‐field potential when the IAP encounters the musculotendinous junction and slowly dissipates. The leading/trailing dipole model is used to explain qualitatively this study's quantitative clinical and computer simulation findings. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 733–741, 1999.