Time of Day Patterns of Sedentary Activity in 12th Grade Girls

In recent years, the risks associated with sedentary behavior (i.e. obesity, Type II diabetes) have become more recognized. Knowledge of the time-of-day when individuals are most sedentary may be beneficial when designing program interventions to promote and increase physical activity.

Purpose To examine time-of-day patterns of sedentary behavior in high school girls.

Methods High school girls (n=325) wore ActiGraph waist accelerometers (ActiGraph, MTI model 7164, Fort Walton Beach, FL) to measure daily minutes of sedentary, light, moderate physical activity (MVPA), and vigorous physical activity (VPA). Accelerometers were worn for an average of 11 hours per day for 7 days. Data were provided for at least 3 weekdays and 1 weekend day from all girls. For the present study, hourly averages of sedentary activity were analyzed on week day and weekend days.

Results A significant time-of-day sinusoidal trend was observed for both the weekday and weekend data. Relatively high levels of sedentary behavior were seen in the morning and evening (especially in the morning) on both the weekday and weekend. The least sedentary behavior was observed between 3-9 pm on weekdays and between 11 am-8 pm on weekend days.

Conclusions Relatively higher levels of sedentary behavior were seen in the morning and evening, especially in the early morning. Potentially, replacing this sedentary activity with moderate or vigorous exercise could have significant benefits.