Lu Dawei, Le Peter, Davidson Bradley, Zhou Bing He, Lu Yun, Patel Vikas, Solomonow Moshe
Musculoskeletal Disorders Research Laboratory, Bioengineering Division, Department of Orthopaedic Surgery, University of Colorado at Denver Health Sciences Center, 12800 East 19th Avenue, Aurora, CO 80045, USA.
Muscle Nerve. 2008 Jul;38(1):867-74. doi: 10.1002/mus.21019.
Epidemiologic studies indicate that repetitive (cyclic) occupational activities lead to a cumulative trauma disorder (CTD), and the frequency or velocity of the movement is one of the risk factors. Experimental neurophysiological evidence to confirm the epidemiology is not available. The response of the multifidus muscles to cyclic loading in anterior lumbar flexion-extension was assessed to test the hypothesis that high-frequency loading may induce an acute neuromuscular disorder leading to CTD. Two groups of feline preparations were subjected to cyclic loading with a peak of 20 N: one at 0.25 HZ and the second at 0.5 HZ, with an equal number of cycles. Electromyogram (EMG), lumbar displacement and load were recorded throughout the loading periods and during single-cycle tests over a 7-hour rest period following the load-rest sessions. A model was developed to quantify the creep and neuromuscular responses, and analysis of variance (ANOVA) was applied to assess significance of the results. The group exposed to 0.5 HZ exhibited spontaneous spasms followed by sustained spasms during the loading periods. During the 7-hour recovery period, a significant (P < 0.001) delayed hyperexcitability as well as sustained spasms of the multifidi were present in the last 5 hours, confirming a significant (P < 0.024 to P < 0.042) acute neuromuscular disorder. High-frequency cyclic loading of the lumbar spine may trigger a severe acute neuromuscular disorder, as evidenced by the sustained spasms and delayed hyperexcitability, and should be considered as a risk factor. We suggest that workers avoid high-frequency exposure to cyclic activity in order to prevent the development of cumulative trauma disorder.
流行病学研究表明，重复性（周期性）职业活动会导致累积性创伤障碍（CTD），而运动的频率或速度是风险因素之一。目前尚无实验神经生理学证据来证实这一流行病学观点。本研究评估了多裂肌在前屈-后伸腰椎运动中对周期性负荷的反应，以检验高频负荷可能诱发导致CTD的急性神经肌肉障碍这一假设。两组猫科动物实验对象接受了峰值为20 N的周期性负荷：一组频率为0.25 Hz，另一组为0.5 Hz，循环次数相同。在整个负荷期以及负荷-休息期后的7小时休息期内的单周期测试中，记录肌电图（EMG）、腰椎位移和负荷。建立了一个模型来量化蠕变和神经肌肉反应，并应用方差分析（ANOVA）来评估结果的显著性。暴露于0.5 Hz的组在负荷期出现了自发性痉挛，随后是持续性痉挛。在7小时的恢复期内，最后5小时多裂肌出现了显著（P < 0.001）的延迟性过度兴奋以及持续性痉挛，证实了存在显著（P < 0.024至P < 0.042）的急性神经肌肉障碍。腰椎的高频周期性负荷可能引发严重的急性神经肌肉障碍，持续痉挛和延迟性过度兴奋就是证据，应将其视为一个风险因素。我们建议工人避免高频接触周期性活动，以预防累积性创伤障碍的发生。
