Department of Rehabilitation and Movement Science, University of Vermont, Burlington, VT, USA.
Exp Brain Res. 2012 Sep;221(4):413-26. doi: 10.1007/s00221-012-3183-8. Epub 2012 Aug 9.
Individuals with a history of non-specific low back pain (LBP) while in a quiescent pain period demonstrate altered automatic postural responses (APRs) characterized by reduced trunk torque contributions and increased co-activation of trunk musculature. However, it is unknown whether these changes preceded or resulted from pain. To further delineate the relationship between cyclic pain recurrence and APRs, we quantified postural responses following multi-directional support surface translations, in individuals with non-specific LBP, following an active pain episode. Sixteen subjects with and 16 without LBP stood on two force plates that were translated unexpectedly in 12 directions. Net joint torques of the ankles, knees (sagittal only), hips, and trunk, in the frontal and sagittal planes, were quantified and the activation of 12 muscles of the lower limb unilaterally and the dorsal and ventral trunk, bilaterally, were recorded using surface electromyography (EMG). Peaks and latencies to peak joint torques, rates of torque development (slopes), and integrated EMGs characterizing baseline and active muscle contributions were analyzed for group by perturbation direction (torques) and group by perturbation by epoch interaction (EMG) effects. In general, the LBP cohort demonstrated APRs that were of similar torque magnitude and rate but peaked earlier compared to individuals without LBP. Individuals with LBP also demonstrated increased muscle activity following perturbation directions in which the muscle was acting as a prime mover and reduced muscle activity in opposing directions, proximally and distally, with some proximal asymmetries. These altered postural responses may reflect increased muscle spindle sensitivity. Given that these motor alterations are demonstrated proximally and distally, they likely reflect the influence of central nervous system processing in this cohort.
在静止疼痛期有非特异性下背痛（LBP）病史的个体表现出改变的自动姿势反应（APR），其特征为躯干扭矩贡献减少和躯干肌肉协同激活增加。然而，尚不清楚这些变化是先于疼痛发生还是由疼痛引起的。为了进一步阐明周期性疼痛复发与 APR 之间的关系，我们在经历活跃疼痛期后，量化了非特异性 LBP 个体在多向支撑面平移后的姿势反应。16 名有和 16 名无 LBP 的受试者站在两个力板上，这两个力板出乎意料地在 12 个方向上平移。在额状面和矢状面量化了踝关节、膝关节（仅矢状面）、髋关节和躯干的净关节扭矩，并使用表面肌电图（EMG）记录了下肢 12 块肌肉的单侧激活情况以及双侧背侧和腹侧躯干。分析了峰值和达到峰值扭矩的潜伏期、扭矩发展速率（斜率）以及基线和活跃肌肉贡献的积分 EMG，以观察组间由扰动方向（扭矩）和组间由扰动时程交互作用（EMG）引起的影响。一般来说，LBP 组的 APR 具有相似的扭矩大小和速率，但与无 LBP 个体相比，峰值更早出现。LBP 个体在肌肉作为主动肌的扰动方向上表现出增加的肌肉活动，而在相反方向、近端和远端表现出减少的肌肉活动，有些近端存在不对称性。这些改变的姿势反应可能反映出肌肉梭敏感增加。鉴于这些运动改变在近端和远端都有表现，它们可能反映了中枢神经系统处理在该队列中的影响。
