Reliability and validity of the five-repetition sit-to-stand test for children with cerebral palsy

Objective: To investigate the psychometric properties of the five-repetition sit-to-stand test, a functional strength test, in children with spastic diplegia. Design: Methodology study. Settings: Hospital, laboratory or home. Participants: In total, 108 children with spastic diplegia and 62 with typical development aged from five to 12 years were tested. For test-retest reliability, 22 children with spastic diplegia were tested twice within one week. Interventions: Not applicable. Main measures: The five-repetition sit-to-stand test measures time needed to complete five consecutive sit-to-stand cycles as quickly as possible. The higher the rate of five-repetition sit-to-stand (repetitions per second), the more strength a person has. Results: The intraclass correlation coefficients of intra-session reliability and test-retest reliability were 0.95 and 0.99 respectively. The minimal detectable difference was 0.06 rep/sec. The convergent validity of the five-repetition sit-to-stand test was supported by significant correlation with one-repetition maximum of the loaded sit-to-stand test, isometric muscle strength, scores of Gross Motor Function Measure, and gait function (r or rho = 0.40-0.78). For known group validity, children with typical development and children classified as Gross Motor Function Classification System level I performed higher rates of five-repetition sit-to-stand than children classified as level II, and children classified as level II performed higher rates than level III. Conclusion: The five-repetition sit-to-stand test was a reliable and valid test to measure functional muscle strength in children with spastic diplegia in clinics.