Functional strength measurement in cerebral palsy: feasibility, test-retest reliability, and construct validity

Purpose: No instrument exists that measures functional strength in both lower and upper extremities in children with cerebral palsy (CP). Therefore, the functional strength measurement (FSM) was tested for feasibility, test-retest reliability and validity in CP. Methods: Thirty-seven children with CP (aged 4-10 years, Gross Motor Function Classification System I and II) participated. The most common compensations for CP were described; new item descriptions were standardized, and one item was removed. Test-retest reliability was examined. To measure convergent validity, correlations between the FSM-CP and isometric muscle strength measured with the handheld dynamometer (HHD) were determined. Results: Test-retest reliability was considered high for all items (intra-class correlation coefficient 0.79-0.95). Significant correlations between the HHD and FSM-CP ranged from r = 0.36 to 0.75. Conclusion: The FSM-CP is feasible, reliable, and valid to use in children with CP. The FSM-CP can be considered as a helpful tool in clinical practice of physical examination of children with CP.