The 24‐h movement behaviours composition is associated with parasympathetic modulation in preschoolers

Aim: To investigate the associations between 24-h movement behaviours and heart rate variability (HRV) in preschool children. Methods: A total of 123 preschoolers (4.52 ± 0.25 years old; 62 girls) were assessed for physical activity (PA) and sedentary behaviour (SB) using an accelerometer (Actigraph WGT3x). Sleep duration (SD) was parent-reported. Children were laid down in a supine position for 10 min to assess HRV data. The R–R intervals recorded during the last 5 min of this period were analysed. We conducted compositional analysis in R studio, and the significance level was 95%. All ethical procedures were followed, and the study had the approval of the local ethical board. Results: When considered as a composition, adjusted for age, body mass index and sex, the 24-h movement composition (PA, SB and SD) significantly predicted better parasympathetic modulation (Root mean square of the successive differences [RMSSD] [p = 0.04; r ² = 0.13]), but not high frequency (HF) (nu) (p = 0.51, r ² = 0.01), low frequency (nu) (p = 0.52, r ² = 0.02),or standard deviation (standard deviation of normal-to-normal intervals) (p = 0.55, r ² = 0.02), respectively. Conclusion: These results suggest the 24-h movement composition predicted the RMSSD time-domain index related to parasympathetic activity.