31st Jan 2024

Introduction: Daily access to opportunities for physical activity (PA) and limited sedentary behaviour (SB) are recommended for health benefits in children. However, it is necessary to understand the day-to-day variability and how children from different socioeconomic groups accumulate these behaviours. Methods: This cross-sectional study included children aged five to 11 years, attending 37 primary schools in Bradford, UK. 800 children wore accelerometers over seven consecutive days, and day-to-day variability was calculated for each participant using the coefficient of variation (calculated as [standard deviation/mean of SB/MVPA across seven measurement days]*100%). Higher coefficient of variation percentages indicates higher variability and therefore low regularity of day-to-day moderate-to-vigorous physical activity (MVPA) and SB. The analysis included comparisons across behavioural indicators and sex, school year, and ethnicity (p<0.05). Results: Lower average values for MVPA (59.9 min/day), higher variability (42.5% vs 33.8%), and higher average values for SB (397.6 min/day) were observed in girls. Conversely, boys showed higher variability for SB (14.3%). Significant differences in MVPA averages were identified among children in school years 1, 2, and 3 (ages 5, 6, and 7 years old), and children from higher school years had higher averages for SB (370.9, 384.4, and 411.1 min/day). Regarding ethnicity, South Asian children had lower MVPA average compared to White British children (63.0 vs. 69.9 min/day), higher variability (40.9% vs. 36.4%), and higher SB average compared to all groups (400.3 min/day). Conversely, SB variability of White British children was higher (14.3% vs. 13.5%). Conclusion: Average daily and variability in MVPA and SB differed across sex, school year, and ethnicity of primary school children, indicating that girls and South Asian children are less active and more sedentary, and have less stability in daily patterns of physical activity.