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.

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Objectives-To investigate associations between objectively measured physical activity (PA) and myopia in children.Methods-Children from the Avon Longitudinal Study of Parents and Children (ALSPAC) were asked to wear a uniaxial accelerometer for seven days. Measures of counts per minute (cpm), minutes spent in moderate to vigorous activity (MVPA) and minutes of sedentary behaviour (msed) were derived from the accelerometer worn at age 12. Children were also examined, at age 10, using an autorefractor to estimate myopia. Social and parental factors were collected from pregnancy and physical measures of the child were recorded at age 12.Results-4880 children had valid PA and autorefraction data. In minimally adjusted models (age and gender) myopic children were less active than the other children: B= −49.9 cpm (95% CI −73.5, −26.4. p=<0.001). The myopic group spent less time in MVPA than the other children, B= −3.2 minutes MVPA (95% CI −5.2, −1.1. p=0.003) and more time sedentary: B= 15.8 minutes (95% CI 5.8, 25.8. p=0.002). The effect sizes were attenuated by adjustment for social and behavioural confounders although myopia status in the better (least myopic on autorefraction) eye remained strongly associated with cpm and MVPA but less so for sedentary behaviour. B= −36.8 cpm (95% CI -67.8, −5.8. p=0.02), B= −2.7 MVPA (95% CI −5.3, −0.1. p=0.04), B= 10.1 msed (95% CI -2.9, 23.1. p=0.13).Conclusion-Myopic children may be at risk of having lower levels of PA than their nonmyopic peers although the difference was modest.

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