Mechanical work, energetic cost, and gait efficiency in children with cerebral palsy.

Many authors have reported increased energy expenditure during walking in children with hemiplegia. The origin of this increase is not well documented. The aim of our study was to understand better the origin of this increased energy expenditure of walking in children with cerebral palsy (CP) by simultaneously assessing the total mechanical work performed by the muscles and the efficiency of the work production.Twenty independently walking children with spastic, hemiplegic CP and a dynamic foot equinus deformity participated in the study. Instrumented gait analysis, including the analysis of kinematic, mechanical, and energetic variables, was performed. Despite excellent Gross Motor Function Measurement scores (range, 97-99), the energy cost was 1.3 times greater in children with CP than in healthy children. This increase in energy cost was related to an increase in the total positive mechanical work performed by the muscles and not related to a decrease in the efficiency of this work production. This study shows how segmental impairments (foot spastic equinus) increase the total mechanical work performed by the muscles and the energetic cost and how these segmental impairments contribute to the patient's disability. It is useful to associate the clinical examination, classic gait analysis, mechanical work, and energetic assessment to complete the evaluation of the condition of children with CP.