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Synchronization of low‐ and high‐threshold motor units
Author(s) -
Defreitas Jason M.,
Beck Travis W.,
Ye Xin,
Stock Matt S.
Publication year - 2014
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.23978
Subject(s) - motor unit , isometric exercise , synchronization (alternating current) , mathematics , physics , physical medicine and rehabilitation , medicine , anatomy , physical therapy , combinatorics , topology (electrical circuits)
: We examined the degree of synchronization for both low‐ and high‐threshold motor unit (MU) pairs at high force levels. Methods : MU spike trains were recorded from the quadriceps during high‐force isometric leg extensions. Short‐term synchronization (between −6 and 6 ms) was calculated for every unique MU pair for each contraction. Results : At high force levels, earlier recruited motor unit pairs (low‐threshold) demonstrated relatively low levels of short‐term synchronization (approximately 7.3% extra firings than would have been expected by chance). However, the magnitude of synchronization increased significantly and linearly with mean recruitment threshold (reaching 22.1% extra firings for motor unit pairs recruited above 70% MVC). Conclusions : Three potential mechanisms that could explain the observed differences in synchronization across motor unit types are proposed and discussed. Muscle Nerve 49:575–583, 2014