Teun Remmers

Investigating moderation between determinants of children's outside play | 79 of outside play, and investigated differences in child gender, age, and comparisons with solely accelerometer-based MVPA (24). Future studies are encouraged to replicate this methodology and move on to investigate the influence of the (perceived) physical environment and / or social environment on objective outside play behavior. Regarding the relative contribution of outside play to the total PA, one study recently investigated the relationship between the amount of parent reported outside play and the amount of accelerometer-measured PA. This study reported that more outside play (<1 hour per day versus 1-2 hours per day and >2 hours per day) was related with significantly lower sedentary time and higher PA of both light and moderate-to-vigorous intensity (22). In addition, only one study has estimated the proportion of strenuous PA during outside play in an intervention promoting outside play using special playgrounds and it has reported that approximately 35% of the time spent in outside play was moderate to vigorously active (60). Future studies are encouraged to quantify the contribution of outside play, relative to total PA and other PA domains. It should be noted that this study solely focused on outside play. Therefore, these results are not generalizable to other PA domains such as organized sports and active transport. Outside play cannot be directly associated with the earlier established benefits of PA, such as its relationship with childhood obesity. Nonetheless, considering its multiple benefits such as increased PA (21), motor abilities, and social skills (25-27), outside play arguably contributes to improved childhood health in the long run. Acknowledgements We would like to thank the children and parents that participated in this part of the KOALA Birth Cohort Study. The authors declare that they have no competing interest References 1. WHO. Global recommendations on physical activity for health. World Health Organization 2010:8-10. 2. Bernaards C. Bewegen in Nederland 2000-2010-Resultaten TNO-Monitor Bewegen en Gezondheid (Physical citivty in the Netherlands 2000-2010: results from the monitor physical activity and health). 2011, Leiden: TNO. 3. Pate RR, Freedson PS, Sallis JF, Taylor WC, Sirard J, Trost SG, et al. Compliance with physical activity guidelines: prevalence in a population of children and youth. Annals of Epidemiology. 2002;12(5):303-8. 4. Sallis JF, Prochaska JJ, Taylor WC. A review of correlates of physical activity of children and adolescents. Medicine & Science in Sports & Exercise. 2000;32:963- 75. 5. DiLorenzo TM, Stucky-Ropp RC, Vander Wal JS, Gotham HJ. Determinants of exercise among children. II. A longitudinal analysis. Preventive Medicine. 1998;27(3):470-7.