Bichler E, Celichowski J
Department of Neurobiology, University School of Physical Education, 55 Grunwaldszka Str, 60-352 Poznan, Poland.
J Electromyogr Kinesiol. 2001 Dec;11(6):387-94. doi: 10.1016/s1050-6411(01)00025-6.
The influence of activity-related changes in tension on properties of the mechanomyogram (MMG) was investigated in fast fatigue-able, fast resistant and slow motor units (MUs). A standard fatigue test was used in which rhythmically repeated unfused tetani were evoked. The amplitudes of the rise in tension of the first and the last contraction within the unfused tetanus and the amplitudes of accompanying signals in MMG were calculated. For fast fatigue-able MUs a parallel decrease in the amplitudes of both analysed contractions and in the amplitudes of accompanying MMG signals during the fatigue test was observed. For majority of fast resistant MUs at the beginning of the fatigue test a potentiation occurred and this phenomenon increased the tension of the first contraction and of the peak tetanic tension. However, the potentiation coincided also with a decrease of the amplitude of the last contraction in the tension recording of an unfused tetanus. The MMG reflected both, the increase of amplitude of the first contraction and the decrease of the amplitude of the further contractions within the tetanus. The single twitch contraction evoked immediately before and after the fatigue test was additionally recorded. A decrease (fatigue) or an increase (potentiation) of the twitch tension after the fatigue test was reflected by a decrease or an increase in the amplitude of MMG, respectively. However, the fatigue failed to change significantly the time parameters of MMG. To conclude, fatigue and potentiation can occur during activity of fast MUs and both these phenomena involve changes in the amplitude of oscillations in tension of unfused tetani which are reflected in MMG.
在快速易疲劳、快速抗疲劳和慢速运动单位（MU）中，研究了与活动相关的张力变化对肌机械图（MMG）特性的影响。采用标准疲劳试验，诱发有节奏重复的非融合强直收缩。计算非融合强直收缩中第一次和最后一次收缩的张力上升幅度以及MMG中伴随信号的幅度。对于快速易疲劳的运动单位，在疲劳试验期间观察到所分析的两次收缩的幅度以及伴随的MMG信号的幅度平行下降。对于大多数快速抗疲劳运动单位，在疲劳试验开始时出现增强现象，这种现象增加了第一次收缩的张力和强直收缩峰值张力。然而，这种增强也与非融合强直收缩张力记录中最后一次收缩幅度的下降同时出现。MMG既反映了强直收缩中第一次收缩幅度的增加，也反映了后续收缩幅度的下降。另外记录了疲劳试验前后立即诱发的单收缩。疲劳试验后单收缩张力的下降（疲劳）或增加（增强）分别由MMG幅度的下降或增加反映。然而，疲劳并未显著改变MMG的时间参数。总之，快速运动单位活动期间可能出现疲劳和增强，这两种现象都涉及非融合强直收缩张力振荡幅度的变化，且这些变化在MMG中得到反映。
