PDF(Pubmed)
Abstract：
Balance impairments are common in cerebral palsy. When balance is perturbed by backward support surface translations, children with cerebral palsy have increased co-activation of the plantar flexors and tibialis anterior muscle as compared to typically developing children. However, it is unclear whether increased muscle co-activation is a compensation strategy to improve balance control or is a consequence of reduced reciprocal inhibition. During translational perturbations, increased joint stiffness due to co-activation might aid balance control by resisting movement of the body with respect to the feet. In contrast, during rotational perturbations, increased joint stiffness will hinder balance control as it couples body to platform rotation. Therefore, we expect increased muscle co-activation in response to rotational perturbations if co-activation is caused by reduced reciprocal inhibition but not if it is merely a compensation strategy. We perturbed standing balance by combined backward translational and toe-up rotational perturbations in 20 children with cerebral palsy and 20 typically developing children. Perturbations induced forward followed by backward movement of the center of mass. We evaluated reactive muscle activity and the relation between center of mass movement and reactive muscle activity using a linear feedback model based on center of mass kinematics. In typically developing children, perturbations induced plantar flexor balance correcting muscle activity followed by tibialis anterior balance correcting muscle activity, which was driven by center of mass movement. In children with cerebral palsy, the switch from plantar flexor to tibialis anterior activity was less pronounced than in typically developing children due to increased muscle co-activation of the plantar flexors and tibialis anterior throughout the response. Our results thus suggest that a reduction in reciprocal inhibition causes muscle co-activation in reactive standing balance in children with cerebral palsy.
摘要：
平衡障碍在脑瘫中很常见。当平衡受到向后支撑表面平移的干扰时，与通常发育中的儿童相比,患有脑瘫的儿童足底屈肌和胫骨前肌的共激活增加.然而,目前尚不清楚增加的肌肉共激活是改善平衡控制的补偿策略还是减少的相互抑制的结果.在平移扰动期间，由于共同激活而增加的关节刚度可能通过抵抗身体相对于脚的运动来帮助平衡控制。相比之下,在旋转扰动期间，增加的关节刚度将阻碍平衡控制，因为它将身体耦合到平台旋转。因此,我们预计，如果共激活是由减少的相互抑制引起的，而不是仅仅是一种补偿策略，则对旋转扰动的反应会增加肌肉共激活。我们通过对20名CP儿童和20名TD儿童的向后平移和脚趾向上旋转扰动来干扰站立平衡。扰动引起的向前运动，然后质心向后运动。我们使用基于质心运动学的线性反馈模型评估了反应性肌肉活动以及质心运动与反应性肌肉活动之间的关系。在通常发育中的儿童中，扰动诱导足底屈肌平衡校正肌肉活动，然后胫骨前平衡校正肌肉活动，它是由质心运动驱动的。在脑瘫儿童中，与通常发育中的儿童相比,足底屈肌向胫骨前活动的转换不那么明显,这是因为足底屈肌和胫骨前肌的肌肉共激活在整个反应过程中增加.因此，我们的结果表明，相互抑制的减少会导致CP儿童反应性站立平衡中的肌肉共激活。
