Functional Strength in Children with Developmental Disabilities: An Exploratory Comparison of Three Clinical Cohorts Including Children with Developmental Coordination Disorder, Intellectual Disabilities, and Cerebral Palsy

Background: This study presents an exploratory comparison of data from three previously collected clinical cohorts. The first aim was to compare functional strength performance among a cohort of children with Developmental Coordination Disorder (DCD), Intellectual Disabilities (ID), and Cerebral Palsy (CP). The second aim was to examine whether the associations between age and functional strength performance differed across these cohorts. Methods: Data from 103 children aged 7–10 years (29 DCD, 47 ID, 27 CP) were combined. Functional Strength Measurement (FSM, FSM-ID, FSM-CP) scores were compared with reference norms. Cohort differences were examined using multivariate analysis of covariance (MANCOVA) with body weight included as a covariate. Associations between age and FSM performance were examined using General Linear Models including age, clinical cohort, and age-by-cohort interaction terms. Results: Compared with the FSM reference norms, 17–89% of participants were classified as impaired or at risk for muscle-power performance, while 62–92% demonstrated limitations in muscle-endurance tasks. Significant differences between the three clinical cohorts were observed for overarm throwing, underarm throwing, lifting a box, and stair climbing, with medium effect sizes. Evidence for age-by-cohort interactions was observed for overarm throwing, underarm throwing, standing long jump, and sit-to-stand performance, indicating that associations between age and functional-strength performance differed across clinical cohorts. Conclusions: Children in the clinical cohorts demonstrated lower levels of functional-strength performance than typically developing peers. Functional-strength profiles differed across clinical cohorts. However, as the data were derived from three distinct cohorts rather than collected within a single study, and minor differences exist between the FSM, FSM-ID and FSM-CP, the findings should be interpreted with caution and considered hypothesis-generating rather than confirmatory. Furthermore, because the data were cross-sectional, no conclusions can be drawn regarding developmental changes over time. These findings may help generate hypotheses for future assessment, intervention and longitudinal research in children with developmental disabilities.