Abstract
INTRODUCTION: This study explores the test-retest reliability of the FITness in PREschoolers (PREFIT) battery, including cardiorespiratory fitness [20 m shuttle run test (SRT)], upper-body muscle strength (handgrip strength), lower-body explosive strength (standing long jump), speed (4 × 10 m shuttle run), and static balance (one-leg stance), in Chilean preschoolers considering weight status, sex, and age. METHODS: The study included 171 Chilean preschoolers (5.4 ± 0.7 years). The PREFIT battery was applied using a test-retest design within 7-10 days between evaluations, and weight status was determined using BMI z-scores (ClinicalTrials.gov: NCT04269135). Statistical analyses included test-retest differences, Lin's concordance correlation coefficient, Cohen's effect size (d), standard error of measurement, intraclass correlation coefficient (ICC), and Bland-Altman plots. Analyses were performed using STATA. RESULTS: Among the 171 preschoolers (5.4 ± 0.7 years), test-retest reliability ranged from excellent to moderate for handgrip strength (ICC = 0.8502; 95% CI: 0.81-0.90), 4 × 10 m shuttle run test (ICC = 0.7696, 95% CI: 0.71-0.84), and PREFIT 20 m SRT (ICC = 0.6656; 95% CI: 0.58-0.74), but was poor for the one-leg stance test (ICC = 0.46; 95% CI: 0.36-0.63). SEM and MDC95 values indicated that changes of 0.85 kg, MDC = 9,502.35 kg (handgrip strength), ≥0.89 s (4 × 10 m shuttle run test), ≥5.33 laps (20 m shuttle run test), and ≥12.43 cm (standing long jump) exceeded measurement error. Reliability was similar across sex, age, and weight-status groups. Bland-Altman analyses showed proportional bias and heteroscedasticity for the 20 m shuttle run test and one-leg stance. At the same time, the remaining tests demonstrated consistent measurement error throughout the performance spectrum. CONCLUSION: The PREFIT battery is appropriate for field application among Chilean preschool children, except for the one-leg stance test, which demonstrated inadequate reliability and proportional bias. Reporting MDC95 enables the interpretation of significant change within educational and intervention contexts.