Willaert Jente, Ting Lena H, Van Campenhout Anja, Desloovere Kaat, De Groote Friedl
Department of Movement Sciences, KU Leuven, Leuven, Belgium.
Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Tech, Atlanta, Georgia, United States.
J Neurophysiol. 2025 Jul 1;134(1):118-127. doi: 10.1152/jn.00568.2024. Epub 2025 Jun 11.
Joint hyper-resistance is a common symptom in cerebral palsy (CP). It is assessed by rotating the joint of a relaxed patient. Joint rotations also occur when perturbing functional movements. Therefore, joint hyper-resistance might contribute to reactive balance impairments in CP. Our aim was to investigate relationships between altered muscle responses to isolated joint rotations and perturbations of standing balance in children with CP. Twenty children with CP and 20 typically developing children participated in the study. During an instrumented spasticity assessment, the ankle was rotated as fast as possible from maximal plantarflexion toward maximal dorsiflexion. Standing balance was perturbed by backward support-surface translations and toe-up support-surface rotations. Gastrocnemius, soleus, and tibialis anterior electromyography were measured. We evaluated alterations in reciprocal pathways by plantarflexor-dorsiflexor coactivation and the neural response to stretch by average muscle activity. We evaluated the relation between muscle responses to ankle rotation and balance perturbations using linear mixed models. Coactivation during isolated joint rotations and perturbations of standing balance was correlated in CP but not in typically developing children. The neural response to stretch during isolated joint rotations and balance perturbations was not correlated. Our results suggest that increased coactivation, possibly due to reduced reciprocal inhibition, during isolated joint rotations might be a predictor of altered reactive balance control strategies in CP. It has been challenging to relate altered muscle coordination during functional movements to altered muscle responses to isolated joint rotations in children with cerebral palsy. We performed more comprehensive assessments by not only considering mean muscle activity but also agonist-antagonist coactivation. Our results indicate that muscle coactivation during balance control might partly result from altered reciprocal pathways, for example, reduced reciprocal inhibition, in the spinal cord. These insights could improve clinical assessments of balance impairments.
关节过度抵抗是脑瘫（CP）的常见症状。通过旋转放松状态下患者的关节来进行评估。在干扰功能性动作时也会出现关节旋转。因此，关节过度抵抗可能导致脑瘫患者的反应性平衡障碍。我们的目的是研究脑瘫儿童中孤立关节旋转时肌肉反应改变与站立平衡扰动之间的关系。20名脑瘫儿童和20名发育正常的儿童参与了该研究。在仪器化痉挛评估过程中，将踝关节从最大跖屈尽可能快地旋转至最大背屈。通过向后平移支撑面和向上旋转支撑面来干扰站立平衡。测量腓肠肌、比目鱼肌和胫骨前肌的肌电图。我们通过跖屈肌 - 背屈肌共同激活评估交互通路的改变，并通过平均肌肉活动评估对拉伸的神经反应。我们使用线性混合模型评估肌肉对踝关节旋转的反应与平衡扰动之间的关系。在脑瘫儿童中，孤立关节旋转时的共同激活与站立平衡扰动相关，而在发育正常的儿童中则无此相关性。孤立关节旋转和平衡扰动期间对拉伸的神经反应不相关。我们的结果表明，在孤立关节旋转期间，可能由于交互抑制减少导致的共同激活增加，可能是脑瘫患者反应性平衡控制策略改变的一个预测指标。将脑瘫儿童功能性动作期间改变的肌肉协调与孤立关节旋转时改变的肌肉反应联系起来一直具有挑战性。我们不仅考虑平均肌肉活动，还考虑了 agonist - antagonist 共同激活，从而进行了更全面的评估。我们的结果表明，平衡控制期间的肌肉共同激活可能部分源于交互通路的改变，例如脊髓中交互抑制的减少。这些见解可能会改善对平衡障碍的临床评估。
