The relation of energy cost of walking with gait deviation, asymmetry, and lower limb muscle co-activation in children with cerebral palsy: a retrospective cross-sectional study

BACKGROUND: Compared to typically developing children, children with cerebral palsy (CP) have increased energy expenditure during walking, limiting activity and participation. Insight into whether the also deviating and more asymmetric gait with increased muscle co-activation contributes to this increased energy expenditure is important for clinical decision making. The aim of this study was to investigate the relation between energy cost of walking with gait deviation, asymmetry, and muscle co-activation in children with CP. METHODS: Forty ambulant children with CP, with Gross Motor Function Classification System (GMFCS) level I (N = 35) and II (N = 5), aged between 5-17y, were tested at one or two occasions with 24 weeks in between, resulting in 71 observations. Gross energy cost (J/kg/m) was measured during a 5-min walk test at self-selected speed. From a 3-dimensional gait analyses, kinematic variables and electromyography were extracted to calculate the gait deviation index (GDI) and co-activation index. The relation between energy cost and GDI, GDI asymmetry, and co-activation index of the lower limb muscles was evaluated through mixed model analyses. Height was included to control for growth-related variation. RESULTS: Gait deviation and height combined explained about 40% of the variance in gross energy cost. No significant contribution was found for gait asymmetry or co-activation index. CONCLUSIONS: This cross-sectional study indicates that increased gait deviation contributes to increased energy cost of walking in children with GMFCS level I and II.