Reallocation of 24‐h Movement Behaviours and Their Effects on Preschoolers' Fundamental Movement Skills: A Compositional Data and Dose–Response Analysis

Background Physical activity (PA), sedentary behaviour (SB) and sleep (SLP)—key components of 24‐h movement behaviours—have each been independently linked to motor development in preschool children. However, the lack of understanding regarding their integrated and mutually exclusive nature has limited research on their combined impact on early health outcomes. This study employed compositional data analysis (CoDA) to examine the relationships between these behaviours and fundamental movement skills (FMS), as well as potential changes in FMS resulting from isotemporal reallocation. Methods A cross‐sectional study was conducted with 292 preschool children (3–6 years old; 149 boys and 143 girls). SB, light physical activity (LPA) and moderate‐to‐vigorous physical activity (MVPA) were measured using accelerometers, whereas sleep duration was parent‐reported. FMS, including locomotor skills, object‐control skills and total motor skills (total MS), were assessed using the third edition of the Test of Gross Motor Development (TGMD‐3). CoDA was used to analyse the relationship between 24‐h movement behaviours and FMS. Results After adjusting for gender, age, family socioeconomic status (SES) and the number of children in the household, a higher proportion of MVPA was significantly positively associated with both total MS ( β = 9.39, p = 0.008) and locomotor skills ( β = 6.69, p = 0.003). In a 15‐min isotemporal reallocation model, substituting MVPA for other behaviours resulted in significant improvements in both total MS and locomotor skills. Dose–response analysis revealed that reallocating even a small amount of time (e.g., 15 min) to MVPA resulted in meaningful benefits for FMS. Notably, this relationship was asymmetric: The negative impact of reducing MVPA outweighed the gains from increasing MVPA. Conclusion These findings highlight the importance of prioritizing MVPA within the 24‐h movement behaviours framework to optimize motor development in preschool‐aged children.