Objective measurement of levels and patterns of physical activity.

OBJECTIVE To measure the levels and patterns of physical activity, using accelerometers, of 11-year-old children participating in the Avon Longitudinal Study of Parents and Children (ALSPAC). DESIGN Cross-sectional analysis. SETTING ALSPAC is a birth cohort study located in the former county of Avon, in the southwest of England. This study used data collected when the children were 11 years old. PARTICIPANTS 5595 children (2662 boys, 2933 girls). The children are the offspring of women recruited to a birth cohort study during 1991-2. The median age (95% CI) of the children is now 11.8 (11.6 to 11.9) years. METHODS Physical activity was measured over a maximum of 7 consecutive days using the MTI Actigraph accelerometer. MAIN OUTCOME MEASURES Level and pattern of physical activity. RESULTS The median physical activity level was 580 counts/min. Boys were more active than girls (median (IQR) 644 (528-772) counts/min vs 529 (444-638) counts/min, respectively). Only 2.5% (95% CI 2.1% to 2.9%) of children (boys 5.1% (95% CI 4.3% to 6.0%), girls 0.4% (95% CI 0.2% to 0.7%) met current internationally recognised recommendations for physical activity. Children were most active in summer and least active in winter (difference = 108 counts/min). Both the mother and partner's education level were inversely associated with activity level (p for trend <0.001 (both mother and partner)). The association was lost for mother's education (p for trend = 0.07) and attenuated for partner's education (p for trend = 0.02), after adjustment for age, sex, season, maternal age and social class. CONCLUSIONS A large majority of children are insufficiently active, according to current recommended levels for health.