Associations of Family Physical Activity Support and 24-Hour Movement Behaviors with Physical Fitness in Preschool Children: A Focus on MVPA

Background/Objectives: Adherence to the 24-h movement guidelines is generally low in preschool children, and less is known about how proximal family support for children’s physical activity (family PA support) is associated with physical fitness and 24-h movement behaviors. This study aimed to describe guideline adherence and to examine the associations among family PA support, 24-h movement behaviors, and physical fitness in Chinese preschool children. Methods: This cross-sectional study included 2386 Chinese preschool children (4.50 ± 0.86 years, 46.8% girls). Family PA support and 24-h movement behaviors were assessed using parent-reported questionnaires, and physical fitness was assessed using the Chinese National Physical Fitness Evaluation Standard for preschool children. Path analysis was used to examine the overall association pattern, including direct and indirect association estimates, among family PA support, movement behaviors, and physical fitness. Results: Only 12.7% of preschool children met all three 24-h movement recommendations. Compliance was 24.7% for physical activity, 82.7% for screen time, and 76.8% for sleep, indicating that insufficient physical activity was the main barrier to full guideline adherence. Family PA support was positively associated with physical fitness (β = 0.048, p = 0.021), and the combined indirect association estimate involving the three movement behaviors was also statistically significant (β = 0.024, p < 0.001). Among the three movement behaviors, family PA support was most strongly associated with higher MVPA (β = 0.150, p < 0.001), and MVPA showed the clearest positive association with physical fitness (β = 0.155, p < 0.001). Screen time was negatively associated with family PA support (β = −0.088, p < 0.001) but not significantly associated with physical fitness (p = 0.091), whereas sleep showed a small negative association with physical fitness (β = −0.056, p = 0.005). These findings suggest a comparatively stronger role for MVPA within the observed association pattern. Conclusion: Chinese preschool children showed low adherence to the 24-h movement guidelines, with insufficient physical activity appearing to be the main limiting factor. Family PA support may represent a potentially modifiable family-level correlate of preschool children’s physical fitness, with MVPA appearing to play a comparatively stronger role within the observed association pattern.