School of Human Kinetics, University of British Columbia, 210-6081 University Boulevard, Vancouver, BC, Canada V6T 1Z1.
Clin Neurophysiol. 2011 Sep;122(9):1794-801. doi: 10.1016/j.clinph.2010.10.050. Epub 2010 Dec 21.
Determine the effect of concentric and eccentric movement and contraction intensity on the strength of rhythmic muscle activity in individuals with essential tremor (ET).
21 ET subjects and 22 healthy controls produced wrist flexion-extension movements while supporting sub-maximal loads (no-load, 5%, 15% and 25% 1-repetition maximum). Kinetic tremor and wrist extensor neuromuscular activity were recorded using an angular displacement sensor and electromyography (EMG).
Rhythmic muscle activity was twice as big during movement compared to previous results involving postural or isometric tasks. ET subjects with greater rhythmic muscle activity had (1) larger overall kinetic tremor amplitude, (2) greater tremor spectral power during eccentric compared to concentric movement and (3) a reduction in overall kinetic tremor amplitude and the percentage of EMG spectral power accounted for by the tremor spectral peak in the presence of inertial loading.
Greater than normal kinetic tremor amplitude appears to be limited to ET subjects with higher levels of rhythmic muscle activity. Furthermore, rhythmic muscle activity is much greater during movement compared to during postural or closed-kinetic tasks.
The strength of rhythmic muscle activity in ET is influenced by the type of contraction (i.e., static vs. dynamic) being performed. Clinicians and researchers should include measures of simple kinetic tremor as part of their assessments.
确定在特发性震颤（ET）患者中，同心和离心运动以及收缩强度对节律性肌肉活动强度的影响。
21 名 ET 受试者和 22 名健康对照者在支撑亚最大负荷（无负荷、5%、15%和 25%1 次最大重复）的情况下进行腕关节屈伸运动。使用角位移传感器和肌电图（EMG）记录运动性震颤和腕伸肌神经肌肉活动。
与涉及姿势或等长任务的先前结果相比，运动期间的节律性肌肉活动增加了一倍。具有更大节律性肌肉活动的 ET 受试者具有：（1）更大的整体运动性震颤幅度，（2）在离心运动时比同心运动时更大的震颤频谱功率，以及（3）在惯性负载存在下，整体运动性震颤幅度和 EMG 频谱功率中震颤频谱峰值所占百分比的减少。
大于正常的运动性震颤幅度似乎仅限于具有更高节律性肌肉活动水平的 ET 受试者。此外，与姿势或闭式运动任务相比，运动期间的节律性肌肉活动要大得多。
ET 中的节律性肌肉活动强度受所进行的收缩类型（即静态与动态）的影响。临床医生和研究人员应将简单运动性震颤的测量作为其评估的一部分。
