TY - JOUR
T1 - Fatigue-related changes in motor-unit synchronization of quadriceps muscles within and across legs
AU - Boonstra, T.W.
AU - Daffertshofer, A.
AU - van Ditshuizen, J.C.
AU - van den Heuvel, M.R.C.
AU - Hofman, C.
AU - Willigenburg, N.W.
AU - Beek, P.J.
PY - 2008
Y1 - 2008
N2 - Two experiments were conducted to examine effects of muscle fatigue on motor-unit synchronization of quadriceps muscles (rectus femoris, vastus medialis, vastus lateralis) within and between legs. We expected muscle fatigue to result in an increased common drive to different motor units of synergists within a leg and, hence, to increased synchronization, i.e., an increased coherence between corresponding surface EMGs. We further expected fatigue-related motor overflow to cause motor-unit synchronization of homologous muscles of both legs, although to a lesser extent than for synergists within a leg. In the first experiment, different levels of fatigue were induced by varying posture (knee angle), whereas in the second experiment fatigue was induced in a fixed posture by instructing participants to produce different force levels. EMG coherence was found in two distinct frequency bands (6-11 and 13-18 Hz) and was higher within a leg than between legs. The fatigue-related increase of 6-11 Hz inter-limb synchronization resembled the increased motor overflow during unimanual contractions and thus hinted at an increase in bilateral coupling. Synchronization at 13-18 Hz was clearly different and appeared to be related to posture. © 2007 Elsevier Ltd. All rights reserved.
AB - Two experiments were conducted to examine effects of muscle fatigue on motor-unit synchronization of quadriceps muscles (rectus femoris, vastus medialis, vastus lateralis) within and between legs. We expected muscle fatigue to result in an increased common drive to different motor units of synergists within a leg and, hence, to increased synchronization, i.e., an increased coherence between corresponding surface EMGs. We further expected fatigue-related motor overflow to cause motor-unit synchronization of homologous muscles of both legs, although to a lesser extent than for synergists within a leg. In the first experiment, different levels of fatigue were induced by varying posture (knee angle), whereas in the second experiment fatigue was induced in a fixed posture by instructing participants to produce different force levels. EMG coherence was found in two distinct frequency bands (6-11 and 13-18 Hz) and was higher within a leg than between legs. The fatigue-related increase of 6-11 Hz inter-limb synchronization resembled the increased motor overflow during unimanual contractions and thus hinted at an increase in bilateral coupling. Synchronization at 13-18 Hz was clearly different and appeared to be related to posture. © 2007 Elsevier Ltd. All rights reserved.
U2 - 10.1016/j.jelekin.2007.03.005
DO - 10.1016/j.jelekin.2007.03.005
M3 - Article
SN - 1050-6411
VL - 18
SP - 717
EP - 731
JO - Journal of Electromyography and Kinesiology
JF - Journal of Electromyography and Kinesiology
IS - 5
ER -