and gender differences in objectively measured physical activity in youth

The purpose of this study was to evaluate age and gender differences in objectively measured physical activity (PA) in a population-based sample of students in grades 1–12. Methods: Participants (185 male, 190 female) wore a CSA 7164 accelerometer for 7 consecutive days. To examine age-related trends, students were grouped as follows: grades 1–3 (N 90), grades 4–6 (N 91), grades 7–9 (N 96), and grades 10–12 (N 92). Bouts of PA and minutes spent in moderate-to-vigorous PA (MVPA) and vigorous PA (VPA) were examined. Results: Daily MVPA and VPA exhibited a significant inverse relationship with grade level, with the largest differences occurring between grades 1–3 and 4–6. Boys were more active than girls; however, for overall PA, the magnitudes of the gender differences were modest. Participation in continuous 20-min bouts of PA was low to nonexistent. Conclusion: Our results support the notion that PA declines rapidly during childhood and adolescence and that accelerometers are feasible alternatives to self-report methods in moderately sized population-level surveillance studies. Key Words: CHILDREN, EXERCISE, ACCELER-OMETER, ASSESSMENT Descriptive epidemiological studies of youth physicalactivity have consistently reported that male sub-jects are more active than female subjects and that physical activity declines with age (18,24). There is, however, considerable disagreement as to the timing and magnitude of these trends (19). This discrepancy may be attributable, in part, to the difficulty associated with measuring physical activity i