Altered muscle synergies during gait in pediatric acquired brain injury: Neurological and biomechanical contributions

This study compared muscle synergies during gait in children with acquired brain injury (ABI) and typically-developing (TD) peers, and examined the influence of gait deviations and injury onset on synergy characteristics. Retrospective treadmill-based 3D gait analysis was conducted in 35 children with ABI in the chronic stage (mean age 11.1 ± 3.7 years; 6.0 ± 4.4 years post-injury) and 21 TD peers. Surface electromyography of seven bilateral lower-limb muscles was analyzed using non-negative matrix factorization. Synergies of the more affected leg were assessed with the dynamic-motor-control-index (walk-DMC), synergy activation patterns, and muscle weights derived from a four-synergy solution. Gait deviations were quantified using the Gait-Profile-Score (GPS) and dimensionless-walking-speed (DWS). The ABI group showed higher GPS (p < 0.001), lower DWS (p = 0.008), reduced walk-DMC (p < 0.001), and altered synergy weights and activation patterns across all four synergies (p ≤ 0.015) compared with TD peers. After controlling for GPS and DWS, most between-group differences were attenuated. Injury onset, whether before or after achieving independent walking, had minimal influence, limited to muscle weights. These findings demonstrate that altered motor control after pediatric ABI is associated with altered neuromuscular coordination and gait impairments following pediatric ABI. This first characterization of synergies in pediatric-ABI highlights the need for longitudinal studies to track neuromechanical changes and guide targeted rehabilitation.