Influence of the Box Dimensions on the Reliability and Validity of the Sit and Reach in Preschoolers

Abstract Ayán Pérez, C, Martínez de Quel, Ó, Álvarez Pérez, S, and González Baamonde, S. Influence of the box dimensions on the reliability and validity of the sit and reach in preschoolers. J Strength Cond Res 34(9): 2683–2692, 2020—This study aimed at analyzing the reliability and validity of the sit and reach (SR) test, when it was performed with a standard SR (SSR) or an adapted SR (ASR) box in preschoolers. To accomplish this, both tests were administered 3 times (familiarization, test, and retest) to a group of 148 children (mean age, 4.99 ± 0.94 years; 49.3% girls), with a week interval between each assessment. The obtained results in each test were compared with those obtained in the passive straight leg raise (PSLR) test with the aim of identifying their construct validity. The internal consistency was found to be between good and excellent for the SSR (α: 0.83–0.92) and excellent for the ASR (α: 0.92–0.96). The SSR showed a good and a fair reliability (intraclass correlation coefficient [ICC], 0.71–0.86), whereas the ASR showed an excellent reliability (ICC, 0.90–0.94) except for the 3-year-old children group (ICC, 0.84). Absolute reliability was excellent for the ASR, whereas the SSR yielded higher SEM and minimum detectable change percentage values. Regarding the criterion-related validity, statistically significant fair correlations were observed between both SR tests and the PSLR test. The ASR yielded higher levels of statistical significance as well as greater correlation coefficients than the SSR. This finding indicates that when it comes to assess flexibility through a low cost and easy-to-implement lineal test in preschoolers, it is advisable to use the SR with a box of reduced dimensions.