Physical Fitness Benchmarks for Preschool Children in South Korea: A Population-Based Study

<b>Background</b>: Physical fitness is vital for children's development and future health. However, Asian preschool-aged populations lack robust physical fitness benchmarks. <b>Objectives</b>: This study aimed to establish age- and sex-specific physical fitness reference values for Korean preschool children and examine associations with anthropometric measures. <b>Methods</b>: A retrospective analysis of data from 36,118 children aged 3 to 6 years was conducted, using five physical fitness tests (Sit and Reach Test, V-Sit Endurance Test, Standing Long Jump, Single-Leg Stand, and 5-Meter Shuttle Run). Percentile curves were generated via Generalized Additive Models for Location, Scale, and Shape (GAMLSS). Relationships between fitness and anthropometric measures were analyzed with LOESS regression. <b>Results</b>: Girls outperformed boys in flexibility, endurance, and balance, while boys excelled in jumping power. Physical fitness improved with age, with performance peaking near average height and weight z-scores. <b>Conclusions</b>: This study provides the first large-scale reference standards for physical fitness in Korean preschoolers, facilitating early identification of fitness deficits and guiding interventions.