The relationships between capacity and performance in youths with cerebral palsy differ for GMFCS levels

Purpose: To examine change in, and longitudinal relationships between motor capacity and activity performance across the Gross Motor Function Classification System (GMFCS). Methods: Ninety-two youths with cerebral palsy were examined at 2 time points, 1 year apart, using the Gross Motor Function Measure-66 (GMFM-66) for motor capacity, and the Chinese version of the Activities Scale for Kids-Performance Version (ASKp-C) for activity performance. The score changes and capacity-to-performance/performance-to-capacity pathways were explored across GMFCS levels. Results: The GMFM-66 scores declined over time in GMFCS levels IV-V while ASKp-C scores increased in GMFCS level I. The correlations for both pathways in GMFCS levels I, III, and IV-V were significant with a higher correlation for performance-to-capacity pathway in GMFCS levels IV-V. Conclusions: Longitudinal changes in and relationships between capacity and performance differ between GMFCS levels. The opportunities to perform activities need to be emphasized in GMFCS levels IV-V.