Teun Remmers

Daily weather and children's PA patterns | 91 As we included all valid days in the analyses, participants were allowed to have from one to seven days of consecutive monitoring per school term. In total, 69% of participants had valid data for at least four days and 40% had valid data for seven days across the four school terms. Children provided 4,597 days of PA measurement in total, with 31.8% in winter, 27.9% in spring, 21.2% in summer, and 19.1% in autumn. In total, 156 children (50.8%) provided data at all four school terms, 81 (26.4%) in three, and 54 (17.6%) in two and 16 (5.2%) in one school term. PA and weather elements across the school terms are presented in Table 1. In winter and spring terms, children engaged in significantly more MPA compared to summer and autumn ( p -values < 0.01). In addition, VPA differed significantly across all terms, except for spring versus autumn. VPA was highest in winter, following by spring/autumn, and summer. Weather elements and children’s PA patterns In Table 2, relationships between weather elements and PA are presented. Compared to no rainfall, little rainfall (0.1–7.8 mm) was associated with more MPA and VPA, whereas more rainfall (7.9-46.0 mm) was not associated with MPA and VPA. Higher humidity was consistently related to lower MPA and VPA, and solar radiation was related to higher MPA and VPA. Day length showed no association with PA. As can be observed in Figure 1, temperature showed a significant curvilinear relationship with MPA and VPA (reflecting the linear and quadratic variables of temperature in Table 2). The temperature that corresponded with highest engagement in MPA and VPA was 22 and 20 degrees Celsius, respectively. When analyses were repeated for sedentary time, general results were equally strong but in opposite direction (see Supplemental Table 1 in Appendix 3). When MPA and VPA results were compared to light PA, differences were found regarding temperature (i.e. no decline in light PA observed at temperatures above 25 degrees Celsius), humidity (i.e. no relationship observed) and rainfall (i.e. 7.6-46.0 mm rainfall associated with more light PA) (see Supplemental Table 1 in Appendix 3).