Department of Industrial and Systems Engineering, University at Buffalo, State University of New York, Buffalo, NY 14260, USA.
J Electromyogr Kinesiol. 2010 Aug;20(4):742-9. doi: 10.1016/j.jelekin.2010.03.002. Epub 2010 Mar 29.
Cyclic trunk flexion/extension is known to be a risk factor for low back pain or disorders. Changes in the in vivo low back musculature associated with cyclic flexion/extension have not been adequately examined. The purpose of this study was to investigate the effects of cyclic flexion/extension on muscle activity of the low back extensors by quantifying changes in activation timing and mean amplitude of electromyography (EMG). Trunk flexion angle and EMG were recorded during 30 cyclic flexion/extension movements over a 5 min period, and during isometric extension performed before and after the 5 min period. Mean EMG in isometric extension increased (30% increase in average) significantly after cyclic flexion/extension, confirming a transfer of extension moment from viscoelastic passive tissues to the extensor muscles in isometric extension. However, in the extension phase of cyclic flexion/extension, a significant delay in the re-activation and a decrease in the mean amplitude of EMG were observed. The results of this study, together with findings in previous research, suggest that the biomechanical effects and potential risk associated with cyclic flexion/extension may be sensitive to the task demands. Further research is needed to investigate how different moment generating components function together to compensate for the loss of tissue stiffness under varying task conditions.
循环式躯干屈伸被认为是导致下腰痛或相关疾病的一个危险因素。与循环屈伸相关的活体下腰背肌的变化尚未得到充分研究。本研究旨在通过量化肌电图（EMG）的激活时间和平均幅度的变化，研究循环屈伸对下腰背伸肌肌肉活动的影响。在 5 分钟的时间内，记录了 30 次循环屈伸运动期间的躯干屈角和 EMG，以及在 5 分钟前后进行的等长伸展期间的记录。在循环屈伸后，等长伸展时的平均 EMG 显著增加（平均增加 30%），证实了在等长伸展中，伸展力矩从粘弹性被动组织转移到了伸肌。然而，在循环屈伸的伸展阶段，观察到明显的再激活延迟和 EMG 平均幅度的下降。本研究的结果与之前的研究结果一致，表明与循环屈伸相关的生物力学影响和潜在风险可能对任务需求敏感。需要进一步研究不同的力矩生成组件如何在不同的任务条件下共同作用，以补偿组织刚度的丧失。
