Arendt-Nielsen L, Gantchev N, Sinkjaer T
Department of Medical Informatics, Aalborg University, Denmark.
Electroencephalogr Clin Neurophysiol. 1992 Jun;85(3):166-72. doi: 10.1016/0168-5597(92)90128-x.
The influence of muscle (vastus lateralis) length on the muscle fibre conduction velocity (MFCV) and on muscle fatigue was studied in 8 healthy volunteers. In experiment 1, the electromyographic (EMG) responses were evoked by electrical stimulation of the motor point and recorded by a surface electrode array aligned along the muscle fibre direction. The MFCV (determined by cross-correlation) was measured at knee flexions of 5 degrees (full extension), 45 degrees, 90 degrees and 120 degrees with 3 different extension torques. The MFCV declined with increasing muscle length and increased with increasing background torque at knee flexions from 5 degrees to 90 degrees. From 90 degrees to 120 degrees knee flexion of MFCV tended to increase. In experiment 2, the EMG activity at a static fatiguing contraction (80% MVC) was measured at 45 degrees and 90 degrees knee flexion. The EMG was measured until the subject gave up contracting the muscle (endurance). The largest increase in the RMS amplitude and the fastest decreases in the mean power frequency (MPF) and MFCV were found at 90 degrees flexion. The MVC at 45 degrees knee flexion was 35% lower than at 90 degrees and the time until endurance was approximately twice as long for the 45 degrees contraction. The results indicate that muscle length is an important parameter for the propagation velocity of action potentials and for the development of static muscle fatigue.
在8名健康志愿者中研究了肌肉（股外侧肌）长度对肌纤维传导速度（MFCV）和肌肉疲劳的影响。在实验1中，通过对运动点进行电刺激诱发肌电图（EMG）反应，并由沿肌纤维方向排列的表面电极阵列进行记录。在膝关节屈曲5度（完全伸展）、45度、90度和120度时，使用3种不同的伸展扭矩测量MFCV（通过互相关确定）。在膝关节从5度屈曲到90度时，MFCV随肌肉长度增加而下降，随背景扭矩增加而增加。从90度到120度膝关节屈曲时，MFCV趋于增加。在实验2中，在膝关节屈曲45度和90度时测量静态疲劳收缩（80%最大自主收缩，MVC）时的EMG活动。测量EMG直到受试者放弃收缩肌肉（耐力）。在90度屈曲时发现均方根（RMS）振幅增加最大，平均功率频率（MPF）和MFCV下降最快。膝关节屈曲45度时的MVC比90度时低35%，45度收缩时达到耐力的时间约为90度收缩时的两倍。结果表明，肌肉长度是动作电位传播速度和静态肌肉疲劳发展的重要参数。
