Patterns of daily physical activity during school days in children and adolescents.

The purpose of this study was to examine the weekday patterns of moderate-to-vigorous physical activity (MVPA) in school children and adolescents and determine if there are periods of the day that are representative of their typical MVPA. The sample comprised 84 subjects (boys, n = 30; girls, n = 54), age 8-15 years old. Daily totals for the physical activity variables were calculated by summing the values from 13 hr of physical activity (PA) measurements (9:00-22:00), with 60-min time blocks comprising each day. The MVPA data values were categorized in four daily periods: morning (9:00-11:59), noon (12:00-14:59), late afternoon (15:00-17.59), and evening (18:00-21.59). Our data show that boys participated significantly more in MVPA than girls. Despite no clear patterns or differences among sex being found, girls showed higher percent of time engaged in MVPA during the morning and early afternoon periods (sum of two periods 51.0%), while boys' percent of time engaged in MVPA is higher at late afternoon and evening periods (sum of two periods 53.8%). The principal components analyses showed four distinct components that accounted for 67% of the variance, as follows: school hours (component 1); lunchtime and outside-school activities (component 2); morning time before school period (component 4); and period before bedtime (component 3) appear as distinct periods of the day. In conclusion, the present study shows that boys engaged more in MVPA than girls. Girls tend to be more active during school periods, while boys are more active after school. Copyright 2003 Wiley-Liss, Inc.