1. Predictors of change in children's physical activity: potential targets for intervention Esther van Sluijs, Chris Craggs, Kirsten Corder, Alison McMinn, Andy Jones, Ulf Ekelund, Simon Griffin

2. Physical activity (PA) is important for children’s current and future health * Many children do not meet current PA guidelines of 60 minutes moderate-to-vigorous PA each day ** self-report – 60-70% accelerometry – 0-99% PA declines in late childhood and adolescence *** Physical activity in children *e.g. Jansen et al, IJBNPA 2010; Telema, Obes Facts 2009; Yang et al, IJO 2009 **Ekelund et al, BJSM 2011 ***e.g. Nader et al, JAMA 2008; Jago et al, AJPM 2008; Corder al et, Ped 2010

3. Effects of PA promotion interventions in children have been varied * Knowledge about factors associated with PA change will aid intervention development current data mostly cross-sectional ** Review of prospective studies *** only identified 46 studies few factors studied consistently predominant use of self- or parent-reported PA Promoting physical activity *e.g. Kriemler et al, BJSM 2011; Van Sluijs et al, BJSM 2011 **e.g. Sallis et al, MSSE 2000; Van der Horst et al, MSSE 2007 **Craggs et al, AJPM 2011

4. To study predictors of 1-year change in PA in 10-year old children, using: exposure variables at different levels of influence objectively-measured PA temporal and intensity-specific outcomes Objective

5. Sport, Physical activity and Eating behaviour, Environmental Determinants in Young people (SPEEDY) Population-based sample N=92 schools across Norfolk sampled for environmental heterogeneity invited all Year 5 children (aged 9-10) Data collection at baseline (2007) during 12-week Summer term questionnaires and anthropometry at school measurement session home pack including accelerometer & parent questionnaire Methods – 1 * * Van Sluijs et al., BMC Publ Health 2008

6. Data collection at follow-up (2008) during 12-week Summer term accelerometer and questionnaire sent home Outcome variables change in % wear time spent in moderate PA (MPA: 2000-3999cpm) and vigorous PA (VPA: ≥4000cpm) separate for weekdays and weekends Exposure variables (baseline) Methods – 2

7. Methods – exposure variables Demographic & Biological 5 variables Psychological 5 variables Environmental 8 variables Socio-cultural 9 variables Behavioural 1 variable age sex parental education active travel self-efficacy barriers PA preference home in cul-de-sac availability of parks distance to green space family cohesiveness rules and restrictions electronic equipment

8. Results – descriptive P<0.001 P=0.012 ns Figure: Minutes spent in MPA and VPA at baseline and 1-year follow-up. Both MPA and VPA decreased significantly at weekend days only 755 children provided valid data (≥3 days of 500 minutes) 37% of SPEEDY-1 participants (N=2064) fewer boys and those of lower SES

9. Results – final models NOTES: *p<0.05; **p<0.01; ***p<0.001; BMI: body mass index; HHI: Herfindahl-Hirschmann Index Multilevel linear regression models Models adjusted for baseline PA, sex and school No differences by sex

10. Predictors of change in PA are time- and intensity-specific targets for interventions may vary Few factors associated with changes on weekday influence of school-level factors? less change in PA on weekdays Study has many strengths, but also some limitations: did not assess potential complex associations differential drop-out multiple testing Discussion

11. Interventions to prevent declines in PA in primary school children may focus on: weekend activity family logistical support preventing further declines in those with higher BMI Conclusion

12. ACKNOWLEDGEMENTS Part of this work was undertaken by the Centre for Diet and Activity Research (CEDAR), a UKCRC Public Health Research Centre of Excellence. The SPEEDY study was funded by the National Prevention Research Initiative and the Medical Research Council.