Teun Remmers

98 | Chapter 6 highly variable across the day. Although we accounted for differences between each day of measurement within children (as a repeated term) and thus also for potential differences in sports participation across school terms, the influence of weather elements may still be underestimated by indoor sports participation. Related to this, future studies may also investigate whether the relationship between weather elements and PA is consistent over time. Underestimation of our results may also stem from children’s cycling behavior, which is not well captured by hip-worn accelerometers, but may vary according to weather elements (23). One could also argue that despite this study controlling for weartime, our results may be influenced by differences in weartime across school terms. For example, especially in summer, weartime (and VPA) was lower compared to other school terms. However, sensitivity analyses revealed that no notable changes were detected when models were repeated for low versus high weartime (data not shown). Finally, we were unable to account for the possibility that water-based PA may have influenced our results in warmer periods of the year. The use of extensive PA diaries or combined Global Positioning System (GPS) and accelerometer methodology in future studies may be able to recognize specific types of PA and their context. Implications This study has important implications for future study methodology. As weather influences cannot be controlled, knowledge of its influence on individual PA patterns may inform the design, analysis and interpretation of future studies; especially when investigating PA across diverse meteorological settings and with long follow-up periods. Also, future interventions should not only account for inter-individual-, but also for intra- individual changes of weather elements in their analyses. This study also has implications for countries that often experience high temperatures (>25 degrees Celsius). As this study showed substantially lower levels of PA at these high temperatures, researchers are encouraged to investigate mechanisms behind this inactivity (e.g. parents/schools keeping children inside or children’s own inclination to be less active). Policy makers in these countries are advised to provide infrastructure to promote and support appropriate PA in these temperatures, while being cautious about adverse health effects of high solar radiation and overheating. Acknowledgments The authors gratefully acknowledge the contribution of all participating children and project staff. We also acknowledge Eoin O’Connell for the development of the customized Excel macro. The authors declare that they have no competing interests. Study results and methodology are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Results of the present study do not constitute endorsement by ACSM.