Clinimetric evaluation of the 1-minute sit-to-stand test as a functional performance measure associated with quadriceps strength in children with spastic hemiplegic cerebral palsy

PURPOSE: To evaluate the construct validity, test-retest reliability, and clinical applicability of the 1-minute sit-to-stand test (1-MSTST) as a functional performance-based measure associated with quadriceps strength in ambulatory children with spastic hemiplegic cerebral palsy (GMFCS I-II). Despite its validity, instrumented strength assessment is not always feasible in routine pediatric rehabilitation, highlighting the need for simple functional alternatives. METHODS: In this cross-sectional methodological study with a test-retest design, 78 children aged 12-18 years were assessed. Quadriceps strength was measured using hand-held dynamometry. Functional performance was evaluated using the 1-MSTST, and a work score was calculated by multiplying repetitions by body weight. Construct validity was examined through correlations between work score and quadriceps strength. RESULTS: The 1-MSTST work score correlated strongly with affected limb strength (r = 0.72, p < 0.001) and moderately-to-strongly with the unaffected limb (r = 0.65, p < 0.001). Test-retest reliability was good (ICC = 0.78; 95% CI: 0.69-0.85). The standard error of measurement was 92.6 kg·repetitions and the minimal detectable change at the 95% confidence level was 256.7 kg·repetitions. No adverse events occurred. These findings indicate that the 1-MSTST is significantly associated with quadriceps muscle strength and may reflect functional lower limb performance, rather than serving as a direct measure of isolated muscle strength capacity. CONCLUSION: The 1-MSTST is a valid, reliable, and clinically feasible tool for assessing functional performance related to quadriceps strength in ambulatory children with spastic hemiplegic cerebral palsy. It may serve as a practical complementary tool to instrumented strength assessment, particularly in routine and resource-limited clinical settings.