Children and chrono-exercise: Timing of physical activity on school and weekend days depends on sex and obesity status

Recommendations for physical activity (PA) typically focus on frequency, intensity, duration, and type, but timing (chrono-exercise) is also important. The objective of this study is to describe when children are active on school and weekend days and explore PA timing across sex and body mass index (BMI) categories. 359 children (53% male), aged 9.6 (0.9) y, were categorized as normal weight (>=-1 standard deviations (SD) and <1SD; n = 193), overweight (>= 1SD and <2SD; n = 80), or obese (>= 2SD; n = 86) using WHO BMIz. Moderate-to-vigorous PA (MVPA) was assessed using ActiGraph LS-7164. The results are described as Mean(SD). ANOVA evaluated MVPA across sexes and BMI categories. Normal weight boys were more active than boys with obesity on school (Delta 20.33 min; p < 0.001) and weekend days (Delta 15.04 min; p < 0.05). On school days, significant differences existed between 9:00 h-11:00 h and 12:00 h-14:00 h (p < 0.017), while on weekends, smaller differences existed throughout the day. Girls' MVPA was similar across BMI categories, on all days (p > 0.05). On school days, 12:00 h-13:00 h represented the most active hour for all participants (similar to 14% total daily MVPA). Peak weekend MVPA was distributed across multiple hours. Differences in MVPA timing emerged on school-days and weekends. Timing may be important when examining the nuances of MVPA in relation to sex and bodyweight in children.

Automated summary

This study describes the timing of physical activity for children on school and weekend days and explores the differences in timing across sex and body mass index categories. The results suggest that normal weight boys are more active than boys with obesity, while girls' physical activity levels are similar across different BMI categories. Additionally, there are timing differences in physical activity on school days and weekends.