Sensorimotor Transformations Underlying Reactive Balance Control Are Altered in Children with Cerebral Palsy

Increased co-activation during reactive balance is often observed in children with cerebral palsy (CP). Increased co-activation might be a compensation strategy to improve balance control or a consequence of neural deficits, like reduced reciprocal inhibition. Our goal is to identify the underlying causes of altered muscle coordination in response to balance perturbations in CP. Muscle activity was assessed during perturbed standing balance and during passive ankle rotations in relaxed participants (20 children with CP and 20 typically developing children). We found increased co-activation of plantarflexors and tibialis anterior in CP during rotational perturbations, hindering balance control. This suggests that increased co-activation is not a compensation strategy. We also found that antagonist muscles received common neural drive during perturbed standing and that co-activation during isolated joint rotations and balance perturbations was related. This suggests that reduced reciprocal inhibition in the spinal cord contributes to increased co-activation during perturbed standing.