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首页> 外文期刊>Journal of Biomechanics >FLEXION RELAXATION DURING LIFTING - IMPLICATIONS FOR TORQUE PRODUCTION BY MUSCLE ACTIVITY AND TISSUE STRAIN AT THE LUMBO-SACRAL JOINT
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FLEXION RELAXATION DURING LIFTING - IMPLICATIONS FOR TORQUE PRODUCTION BY MUSCLE ACTIVITY AND TISSUE STRAIN AT THE LUMBO-SACRAL JOINT

机译：举升过程中的屈曲放松-腰S关节肌肉活动和组织应变产生扭矩的含义

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During the full flexion phase of the back lift movement the lumbar part of the erector spinae muscle exhibits a reduced activity level (flexion relaxation). This study addresses the question how the required extension torque in the lumbo-sacral joint (L5/S1 joint) is balanced during the period in which apparently the lumbar erector spinae ceases to take its share. Six subjects participated in the experiment in which they performed seven lifting tasks. The load, the range of movement, and the phase in which the load was handled (lifting or lowering) were varied. A dynamic linked segment model was applied to determine the momentary torques acting at the L5/S1 joint, while the EMGs of the lumbar and thoracic part of the erector spinae muscle were measured. Furthermore, the lengths between markers on the lumbar and thoracic part of the trunk were determined to reveal changes in length during the movement. The dynamic EMGs were normalized to trunk angle-dependent maximal levels. The L5/S1 joint torques were analysed and combined with the normalized EMG data and the kinematics of the trunk, which are assumed to indicate the elongation of passive tissues. Although in the normalization procedure the change of the length-force relationship of the erector spinae was taken into account, the dynamic lumbar EMG activity decreased to a low-activity level (the phenomenon of flexion relaxation). This coincided with a 25% increase in lumbar length suggesting that passive tissue strain provided part of the required extension torque. In the tasks where a barbell was handled a significant increase in EMG level of the thoracic part of the erector spinae occurred just before the flexion relaxation at the lumbar level, Apparently, the extensor function of the lumbar part is then taken over by the thoracic part of the erector spinae muscle. This suggests that an intricate coordinating mechanism is operative that apportions the load to be balanced over active - (lumbar and thoracic part of the erector spinae) and passive structures (post vertebral ligaments). [References: 65]
机译：在向后抬起运动的完全屈曲阶段，竖脊肌的腰部活动水平降低（屈曲松弛）。这项研究解决了一个问题，即在腰直肌显然不再占据其份额的这段时间内，腰-关节（L5 / S1关节）所需的延伸扭矩如何得到平衡。六名受试者参加了该实验，其中他们执行了七项提升任务。负载，移动范围以及处理负载（升高或降低）的阶段都不同。应用动态链接段模型确定作用在L5 / S1关节上的瞬时扭矩，同时测量直立脊柱肌肉的腰部和胸部部分的肌电图。此外，确定腰部和胸部的标志物之间的长度，以揭示运动过程中长度的变化。动态肌电图标准化为躯干角度相关的最大水平。分析了L5 / S1关节扭矩，并将其与归一化的EMG数据和躯干运动学相结合，并认为这表明了被动组织的伸长。尽管在正常化过程中考虑了竖脊肌的长度-力量关系的变化，但动态腰肌电活动降低到低活动水平（屈曲松弛现象）。这与腰部长度增加25％相吻合，表明被动组织张力提供了所需的延伸扭矩的一部分。在处理杠铃的任务中，在腰部屈曲松弛之前，直立脊柱的胸部EMG显着增加，显然，然后，腰部的伸肌功能由胸部承担的脊柱肌肉。这表明，一种复杂的协调机制是有效的，可以在主动结构（竖脊椎的腰部和胸部部分）和被动结构（椎体后韧带）之间分配负载，使其达到平衡。 [参考：65]

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