Palmer College of Chiropractic, Palmer Center for Chiropractic Research, Davenport, IA, USA.
J Electromyogr Kinesiol. 2012 Dec;22(6):814-20. doi: 10.1016/j.jelekin.2012.04.006. Epub 2012 Jun 20.
In the lumbar spine, muscle spindle responsiveness is affected by the duration and direction of a lumbar vertebra's positional history. The purpose of the present study was to determine the relationship between changes in the magnitude of a lumbar vertebra's positional history and the responsiveness of lumbar muscle spindles to a subsequent vertebral position and subsequent vertebral movement. Neural activity from multifidus and longissimus muscle spindle afferents in deeply anesthetized cats was recorded while creating positional histories of the L(6) vertebra. History was induced using a displacement-controlled feedback motor. It held the L(6) vertebra for 4 s at an intermediate position (hold-intermediate at 0 mm) and at seven positions from 0.07 to 1.55 mm more ventralward and dorsalward which lengthened (hold-long) and shortened (hold-short) the lumbar muscles. Following the conditioning hold positions, L(6) was returned to the intermediate position. Muscle spindle discharge at this position and during a lengthening movement was compared between hold-intermediate and hold-short conditionings and between hold-intermediate and hold-short conditionings. We found that regardless of conditioning magnitude, the seven shortening magnitudes similarly increased muscle spindle responsiveness to both vertebral position and movement. In contrast, the seven lengthening magnitudes produced a graded decrease in responsiveness to both position and movement. The decrease to position became maximal following conditioning magnitudes of ∼0.75 mm. The decrease to movement did not reach a maximum even with conditioning magnitudes of ∼1.55 mm. The data suggest that the fidelity of proprioceptive information from muscle spindles in the low back is influenced by small changes in the previous length history of lumbar muscles.
在腰椎中，肌梭的反应性受腰椎位置历史的持续时间和方向的影响。本研究的目的是确定腰椎位置历史的幅度变化与腰椎肌梭对随后的椎体位置和随后的椎体运动的反应之间的关系。在深度麻醉的猫中，从多裂肌和最长肌肌梭传入神经记录神经活动，同时创建 L(6)椎骨的位置历史。历史是通过位置控制反馈电机产生的。它将 L(6)椎骨保持在中间位置（保持中间在 0 毫米）和七个位置，从 0.07 到 1.55 毫米更腹侧和背侧，从而延长（保持长）和缩短（保持短）腰椎肌肉。在条件保持位置之后，将 L(6)返回到中间位置。在这个位置和在伸展运动期间，将保持中间和保持短条件之间以及保持中间和保持短条件之间的肌梭放电进行比较。我们发现，无论调节幅度如何，七个缩短幅度都相似地增加了肌梭对椎体位置和运动的反应性。相比之下，七个延长幅度对位置和运动的反应性呈分级下降。这种对位置的下降在约 0.75 毫米的调节幅度后达到最大值。即使在约 1.55 毫米的调节幅度下，对运动的下降也未达到最大值。数据表明，来自腰椎肌梭的本体感觉信息的保真度受腰椎肌肉先前长度历史的微小变化的影响。
