Energy cost of walking in children with spastic cerebral palsy: relationship with age, body composition and mobility capacity.

The energy cost (EC) of walking is different for typically developing (TD) and children with cerebral palsy (CP). The associated factors of EC are not fully understood in children with CP. We assessed the relationship between EC and age, body surface area (BSA), and gross motor function measure (GMFM). We retrospectively examined data collected between 2003 and 2011 on 276 children aged 4-18 years who were classified as Gross Motor Function Classification System level I, n=79; II, n=123; and III, n=74. Energy cost was assessed while children walked 6-8 min at a comfortable, self-selected speed using their typical walking aids and/or orthoses as part of a clinical gait analysis. During the test, participants wore a breath-by-breath portable gas analysis system, measuring oxygen consumption. To calculate EC (J/kg/m), oxygen consumption was converted to J/kg/min and divided by walking speed. Data were analyzed using linear regression model. Energy cost correlated inversely with age (β=-0.16, R2=0.02, P=0.01), BSA (β=-3.35, R2=0.11, P<0.0001), and GMFM (β=-0.12, R2=0.42, P<0.0001). In the multiple linear regression model, GMFM was the most potent correlate of EC, BSA explained another 10% of the variance (R2=0.53), and age was a marginally significant correlate of EC (P=0.08). In summary, in children with CP in our study, EC decreased as GMFM and BSA increased, and GMFM was the most potent correlate of EC.