Antagonist muscle activity during reactive balance responses is elevated in Parkinson’s disease and in balance impairment

BackgroundAbnormal antagonist leg muscle activity could indicate increased muscle co-contraction and clarify mechanisms of balance impairments in Parkinson’s disease (PD). Prior studies in carefully selected patients showed PD patients demonstrate earlier, longer, and larger antagonist muscle activation during reactive balance responses to perturbations.Research questionHere, we tested whether antagonist leg muscle activity was abnormal in a group of PD patients who were not selected for phenotype and most of whom had volunteered for exercise-based rehabilitation.MethodsWe compared antagonist activation during reactive balance responses to multidirectional support-surface translation perturbations in 31 patients with mild-moderate PD (age 68±9; H&Y 1–3; UPDRS-III 32±10) and 13 matched individuals (age 65±9). We quantified modulation of muscle activity (i.e., the ability to activate and inhibit muscles appropriately according to the perturbation direction) using modulation indices (MI) derived from minimum and maximum EMG activation levels observed across perturbation directions.ResultsAntagonist leg muscle activity was abnormal in unselected PD patients compared to controls. Linear mixed models identified significant associations between impaired modulation and PD (PSignificanceAntagonist activity is increased during reactive balance responses in PD patients who are not selected on phenotype and are candidates for exercise-based rehabilitation. This activity may be a mechanism of balance impairment in PD and a potential rehabilitation target or outcome measure.

背景 下肢拮抗肌活动异常可提示肌肉共同收缩增强，同时有助于阐明帕金森病（Parkinson’s Disease, PD）患者平衡障碍的发生机制。此前针对经严格筛选的患者开展的研究显示，帕金森病患者在应对扰动引发的反应性平衡应答时，其拮抗肌激活出现更早、持续时间更长且激活幅度更大。
研究问题 本研究旨在探讨未按表型筛选的帕金森病患者群体（其中多数为运动康复候选受试者）的下肢拮抗肌活动是否存在异常。
方法 本研究纳入31例轻中度帕金森病患者（年龄68±9岁；Hoehn-Yahr分级（H&Y）1~3级；统一帕金森病评定量表第三部分（Unified Parkinson’s Disease Rating Scale Part III, UPDRS-III）评分32±10）以及13例年龄匹配的健康对照者（年龄65±9岁），对比两组在支撑面多方向平移扰动引发的反应性平衡应答过程中的拮抗肌激活情况。本研究采用基于各扰动方向下肌电图（Electromyography, EMG）的最大与最小激活水平计算得到的调节指数（Modulation Indices, MI），量化肌肉活动调节能力——即根据扰动方向合理激活与抑制肌肉的能力。
结果 与健康对照相比，未按表型筛选的帕金森病患者下肢拮抗肌活动存在异常。线性混合模型分析显示，肌肉调节能力受损与帕金森病存在显著关联。
意义 未按表型筛选且符合运动康复指征的帕金森病患者，在反应性平衡应答过程中拮抗肌活动增强。该异常活动可能是帕金森病患者平衡障碍的病理生理机制之一，同时也可作为潜在的康复干预靶点或疗效评估指标。