Teun Remmers

Daily weather and children's PA patterns | 89 Summer (February-March 2013; Term 1); and Autumn (May-June 2013; Term 2). No data were collected during school holidays. Measurements Physical activity Children’s PA was objectively assessed for seven consecutive days in each school term using hip-mounted ActiGraph GT3X+ accelerometers (Pensacola, FL). Raw tri-axial data were sampled at 30Hz and downloaded and processed into 15 second epochs using ActiLife software (v6). Non-wear time was defined as sustained 20 minute periods of consecutive zero counts (4). Intensity of PA was classified using the following age-specific cut-points agreeing with metabolic equivalents (METs) (10): 1.5-3.99 for light PA (LPA), 4– 5.99 for moderate PA (MPA), ≥ 6 for vigorous PA (VPA). These cut-points have been found to exhibit excellent classification accuracy and are commonly used (30). A valid day was defined as ≥ 8 hours on weekdays and ≥ 7 hours on weekend days. The lower weekend wear time requirement was due to children typically waking later on weekend days (26). For the purpose of this study, all valid days collected from each school term were included in the analyses. Anthropometry Body mass was measured to the nearest 0.1 kg using a calibrated electronic scale (Tanita BC-351; Tanita, Japan). Stature was measured to the nearest 0.1 cm using SECA portable stadiometers (model 217; SECA, Germany). Two measurements of body mass and stature were taken and averaged before calculating BMI (weight/stature 2 , kg/m 2 ). In the event of a discrepancy over 0.1 kg or 1 cm, a third measurement was taken. All measurements were taken by trained research staff using standardized procedures. Meteorological data Meteorological data were obtained for each day of data collection from the publicly accessible Australian Government’s Bureau of Meteorology (2). The nearest weather station to each participating school was identified and data were matched to accelerometer wear days in each school. The data obtained were temperature (daily maximum in °C), relative humidity (daily average in percentage), solar radiation (daily total in MJ/m 2 ), day length (total minutes of daylight per day), and rainfall (daily total in mm). Owing to its highly skewed distribution, rainfall was collapsed into three categories; no rainfall (52.5% of days); and rainfall split into categories of similar size: 0.1-7.8 mm (23.6% of days) and 7.9–46.0 mm per day (23.9% of days). All other weather-variables were treated as continuous variables in subsequent models. Statistical analyses Days were used as the unit of analysis because this allows day to day variation within children. Our primary outcome variables were (continuous) daily total minutes classified as MPA and VPA. Temperature, relative humidity, rainfall, solar radiation, and day length