Importance of analyzing spasticity and co-activation as complementary biomarkers of gait in children with cerebral palsy.

Abstract

Cerebral palsy (CP) is a neurological disorder characterized by motor impairments, including muscle spasticity, weakness, and abnormal co-activation leading to gait abnormalities. Understanding the relationship between these factors is essential for optimizing rehabilitation strategies but remains unclear, particularly in terms of phase-specific neuromuscular adaptations during gait. This study investigated the correlations between muscle spasticity, strength, co-activation, and gait variable scores (GVS) in children with CP during clinical gait analysis. Two muscle pairs were analyzed: Gastrocnemius Medialis-Tibialis Anterior (GM-TA) and Rectus Femoris-Semitendinosus (RF-ST). We retrospectively analyzed 55 children with CP using surface electromyography and clinical scales (Modified Ashworth Scale for spasticity, Medical Research Council scale for strength). Co-activation was computed for stance and swing phases and compared to reference values from literature data about typically developing children. Correlations between variables were assessed using Spearman's coefficient and Chi-square tests evaluated categorical relationships between spasticity and abnormal co-activation. No clear correlations between spasticity and co-activation were demonstrated, except for RF during swing (moderate correlation). GVS for ankle and hip flexion was moderately correlated with co-activation. Muscle strength negatively correlated with co-activation and deviations of joint angles relative to healthy gait. These findings highlight partial correlations between clinical examination (i.e., spasticity and strength) and gait data (i.e., muscle co-activation and kinematic alterations), reinforcing the importance of assessing multiple biomarkers to better characterize gait abnormalities. Future rehabilitation protocols should comprehensively evaluate spasticity, muscle strength, co-activation, and GVS to better adapt interventions and optimize motor function in children with CP.