School of Human Kinetic, University of British Columbia, 210 - 6081 University Boulevard, BC, Canada.
Clin Neurophysiol. 2010 Feb;121(2):233-9. doi: 10.1016/j.clinph.2009.10.015. Epub 2009 Dec 31.
Quantify the effect of increasing contraction intensity on the amplitude of force fluctuations and neuromuscular and force tremor spectral power.
Twenty-one subjects with essential tremor (ET) and 22 healthy controls applied isometric wrist extension contractions. Various sub-maximal contraction intensities were evaluated (5%-, 10%-, 20%- and 30%-MVC). Force fluctuations and wrist extensor neuromuscular activity were recorded using a load cell and electromyography (EMG).
Higher contraction intensities were associated with larger amplitude force fluctuations and greater neuromuscular activation. However, spectral power associated with tremor peaks remained relatively constant (EMG) or decreased (force) with increasing contraction intensity.
Motor unit entrainment associated with centrally generated oscillatory inputs does not increase with greater levels of muscle activation.
Rather than influencing a constant proportion of active motor units, abnormal oscillatory drive influences a relative constant number of total motor units. When combined with the findings from our previous study on postural tremor, the present results provide preliminary evidence that abnormal stretch reflex activity may contribute to this motor unit entrainment.
定量增加收缩强度对力波动幅度以及神经肌肉和力震颤频谱功率的影响。
21 名特发性震颤（ET）患者和 22 名健康对照者进行等长腕伸肌收缩。评估了各种次最大收缩强度（5%、10%、20%和 30%最大收缩力）。使用测力传感器和肌电图（EMG）记录力波动和腕伸肌神经肌肉活动。
更高的收缩强度与更大的力波动幅度和更大的神经肌肉激活相关。然而，与震颤峰相关的频谱功率随着收缩强度的增加保持相对恒定（EMG）或降低（力）。
与中枢产生的振荡输入相关的运动单位同步化不会随着肌肉激活水平的增加而增加。
异常的振荡驱动不是影响恒定比例的活动运动单位，而是影响相对恒定数量的总运动单位。当与我们之前关于姿势性震颤的研究结果结合时，本研究结果初步表明，异常的牵张反射活动可能导致这种运动单位同步化。
