McGill S M, Kippers V
Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo, Ontario, Canada.
Spine (Phila Pa 1976). 1994 Oct 1;19(19):2190-6. doi: 10.1097/00007632-199410000-00013.
This study used an anatomically detailed model of the lumbar tissues, driven from biologic signals of vertebral displacement and myoelectric signals, to estimate individual muscle and passive tissue force-time histories during the performance of the "flexion-relaxation" maneuver. Eight male university students performed three trials each of the "flexion-relaxation" maneuver with six pairs of surface myoelectric electrodes monitoring the right side of the trunk musculature, an electromagnetic device to record lumbar flexion, and videotape to record body segment displacement.
To examine the loads on individual tissues during the transfer of moment support responsibility from predominantly active muscle to predominantly passive tissue.
No previous studies, to the authors' knowledge, have examined individual tissue loading during the flexion-relaxation maneuver.
Although most subjects were able to "relax" their lumbar extensors in full flexion, activity remained in the thoracic extensors and abdominals. Tissue load predictions suggested that while the lumbar extensor muscles were neurally "relaxed" (i.e., myoelectric silence), substantial elastic forces would assist the passive tissues in extensor moment support. On average, subjects sustained almost 3 kN in compressive load on the lumbar spine and about 755 N of anterior shear during full flexion with only 8 kg held in the hands.
The "relaxation" of lumbar extensor muscles appeared to occur only in an electrical sense because they generated substantial force elastically through stretching. Loading of the interspinous and supraspinous ligaments, in particular, was high relative to their failure tolerance.
本研究使用了一个腰椎组织的解剖学详细模型，该模型由椎骨位移的生物信号和肌电信号驱动，以估计在“屈曲-放松”动作执行过程中个体肌肉和被动组织的力-时间历程。八名男性大学生每人进行了三次“屈曲-放松”动作试验，使用六对表面肌电电极监测躯干肌肉组织的右侧，用电磁装置记录腰椎屈曲情况，并用录像带记录身体节段的位移。
研究在力矩支撑责任从主要由主动肌肉转移到主要由被动组织承担的过程中，各个组织所承受的负荷。
据作者所知，此前尚无研究探讨过“屈曲-放松”动作过程中各个组织的负荷情况。
尽管大多数受试者在完全屈曲时能够“放松”其腰椎伸肌，但胸段伸肌和腹部仍有活动。组织负荷预测表明，虽然腰椎伸肌在神经上“放松”（即肌电静止），但大量的弹力会协助被动组织提供伸肌力矩支撑。平均而言，受试者在完全屈曲且手中仅握8千克重物时，腰椎承受近3千牛的压缩负荷和约755牛的前向剪切力。
腰椎伸肌的“放松”似乎仅在电生理意义上出现，因为它们通过拉伸产生了大量弹性力。特别是棘间韧带和棘上韧带的负荷相对于其耐受极限较高。
