Boonstra T W, Daffertshofer A, van Ditshuizen J C, van den Heuvel M R C, Hofman C, Willigenburg N W, Beek P J
Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081BT Amsterdam, The Netherlands.
J Electromyogr Kinesiol. 2008 Oct;18(5):717-31. doi: 10.1016/j.jelekin.2007.03.005. Epub 2007 Apr 25.
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.
进行了两项实验，以研究肌肉疲劳对双腿内及双腿间股四头肌（股直肌、股内侧肌、股外侧肌）运动单位同步性的影响。我们预期肌肉疲劳会导致对同一条腿内协同肌不同运动单位的共同驱动增加，从而使同步性增加，即相应表面肌电图之间的相干性增加。我们还预期与疲劳相关的运动溢出会导致双腿同源肌肉的运动单位同步，尽管程度低于同一条腿内的协同肌。在第一个实验中，通过改变姿势（膝关节角度）诱导不同程度的疲劳，而在第二个实验中，通过指示参与者产生不同的力水平在固定姿势下诱导疲劳。肌电图相干性出现在两个不同的频带（6 - 11赫兹和13 - 18赫兹），并且同一条腿内的相干性高于双腿间的相干性。与疲劳相关的6 - 11赫兹肢体间同步性增加类似于单手收缩期间运动溢出的增加，因此暗示双侧耦合增加。13 - 18赫兹的同步性明显不同，似乎与姿势有关。
