Graduate Programs in Rehabilitation Sciences, University of British Columbia, Vancouver, BC, Canada.
Centre of Clinical Research Excellence in Spinal Pain, Injury and Health, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Queensland, Australia.
Pain. 2018 Nov;159(11):2192-2200. doi: 10.1097/j.pain.0000000000001317.
Movement is changed in pain, but the mechanisms remain unclear. Key questions are unresolved such as whether activation can be inhomogeneously distributed within a muscle in a manner that is specific to the location of noxious input. This study addressed this question using high-density electromyography (EMG) to study regional redistribution of muscle activation within the vasti muscles and changes in knee extension force direction in response to noxious stimulation applied to muscular and nonmuscular tissues around the knee. Fourteen participants performed a low-force knee extension contraction at baseline, during, and after pain induced in 4 locations (infrapatellar fat pad, vastus lateralis, distal vastus medialis, or proximal vastus medialis). The knee extension force direction was estimated from a 3-dimensional load cell positioned just above the ankle. Regional muscle activation was estimated from amplitude of high-density surface EMG signals from vastus medialis and lateralis. Pain-induced spatial variations of activation were identified as the position of the 5 channels that showed the largest decrease (or smallest increase) in amplitude from baseline to pain or after pain. Knee extension force was produced more medially during pain after infrapatellar pad injection only (P = 0.01). Preferential reduction of activation of the distal region of vastus medialis was observed when distal vastus medialis (P < 0.001) or vastus lateralis (P < 0.05) was injected. Both adaptations persisted after pain resolution. These results support the hypothesis that specific adaptation depends on the location of a noxious stimulus and imply that recovery of pain is not necessarily concomitant with return of the EMG to prepain patterns.
运动在疼痛中发生改变，但机制仍不清楚。关键问题尚未解决，例如在肌肉内是否可以以特定于有害刺激输入位置的方式不均匀地分布激活。本研究使用高密度肌电图（EMG）来研究股四头肌内肌肉激活的区域再分布，以及在膝关节周围的肌肉和非肌肉组织施加有害刺激时，膝关节伸展力方向的变化，以解决这个问题。14 名参与者在基线、疼痛期间和疼痛后在 4 个部位（髌下脂肪垫、股外侧肌、股内侧肌远端和股内侧肌近端）进行低强度膝关节伸展收缩。膝关节伸展力方向是从位于踝关节上方的三维负荷细胞估计的。股内侧肌和股外侧肌的高密度表面 EMG 信号的幅度估计了区域肌肉激活。激活的疼痛诱导空间变化被确定为显示从基线到疼痛或疼痛后幅度最大减小（或最小增加）的 5 个通道的位置。只有在髌下脂肪垫注射后，疼痛期间膝关节伸展力更偏向内侧（P = 0.01）。当注射股内侧肌远端（P < 0.001）或股外侧肌（P < 0.05）时，观察到股内侧肌远端区域的激活优先减少。这两种适应在疼痛缓解后仍然存在。这些结果支持特定适应取决于有害刺激位置的假设，并暗示疼痛的恢复不一定与 EMG 恢复到疼痛前模式同时发生。
