Reallocating sedentary time with total physical activity and physical activity bouts in children: Associations with cardiometabolic biomarkers

This cross-sectional study examined theoretical effects of reallocating sedentary time (SED) with total physical activity, and physical activity bouts of varying intensities, on children's cardiometabolic biomarkers. Baseline data from the Transform-Us! trial (Melbourne, Australia) was used. Participant data were included if accelerometer and blood biomarker data were complete (n = 169; 8.7 [0.4] years; 56% girls). Isotemporal substitution models assessed the impact of replacing 10 minutes of SED with 10 minutes of total physical activity or physical activity in bouts of varying intensities on cardiometabolic biomarkers. In adjusted models, replacing 10 minutes of SED with vigorous-intensity physical activity (VPA) was associated with lower triglycerides in the whole sample. Replacing SED with VPA was associated with better high-density lipoprotein cholesterol (HDL-C) and triglycerides in children with healthy weight. Replacing SED with MPA was associated with better homoeostatic model assessment of insulin resistance (HOMA-IR) and HDL-C, in children with healthy weight and overweight, respectively. Substituting SED with VPA specifically accumulated in ≥1-min bouts was detrimentally associated with HOMA-IR in children with healthy weight but beneficially with the cardiometabolic summary score in the overweight sample. This suggests that replacing SED with MPA or VPA may have some benefits on cardiometabolic health.