Associations between physical activity, body composition and physical fitness in the transition from preschool to school.

The purpose of the study was to assess the longitudinal associations of physical activity (PA) with body composition and physical fitness (PF) at the 12-month follow-up during the transition from kindergarten to school in Estonian children aged 6 to 8 years (n=147). PAand sedentary behaviour (SB) were assessed using the accelerometer. Body composition was measured from triceps and subscapular skinfold thicknesses and PF using PREFIT test battery. SB at the mean age of 6.6 yr had negative relation with upper and lower body strength and motor fitness at the mean age of 7.6 yr in adjusted models. Light PA (LPA) and moderate PA(MPA) at 6.6 yr were positively and SB was negatively associated with fat-free mass index (FFMI) at 7.6 yrafter adjustments for confounders[vigorous PA (VPA), total awake wear time, child's sex, age at measurement]. Substituting 5 min/day of SB at 6.6 yr with 5 min of VPA was related to higher FFMI at 7.6 yr. In adjusted models, VPA at 6.6 yr waspositively associated with cardiorespiratory fitness at 7.6 yr,greaterbaseline VPA ormoderate-to-vigorous PA (MVPA)predicted greater upper body strength a year later and LPA, MPA, VPA, MVPA at 6.6 yrwere positively related to lower body strength at follow-up.In adjusted analysis greater VPA at 6.6 yr was related to better motor fitnessat follow-up. Promoting higher-intensity PA and reducing SB at preschool may have long-term effects on body composition and PF in children at the first grade.