Individual calibration of accelerometers in children and their health-related 2 implications

This study compared children’s physical activity (PA) levels, the prevalence of children 73 meeting current guidelines of ≥60 minutes of daily moderate to vigorous PA (MVPA), and 74 PA-health associations using individually calibrated (IC) and empirical accelerometer 75 cutpoints. Data from 75 (n = 32 boys) 10-12 year old children were included in this study. 76 Clustered cardiometabolic (CM) risk, directly measured cardiorespiratory fitness (CRF), 77 anthropometric and 7 day accelerometer data were included within analysis. PA data were 78 classified using Froude anchored IC, Evenson et al., 2008 (Ev) and Mackintosh et al., 2012 79 (Mack) cutpoints. The proportion of the cohort meeting ≥60mins MVPA/day ranged from 80 37%-56% depending on the cutpoints used. Reported PA differed significantly across the 81 cutpoint sets. IC LPA and MPA were predictors of CRF (LPA: standardised β = 0.32, p = 82 0.002, MPA: standardised β = 0.27 p = 0.013). IC MPA also predicted BMI Z-score 83 (standardised β = -0.35, p = 0.004). Ev VPA was a predictor of BMI Z-score (standardised β 84 = -0.33, p = 0.012). Cutpoint choice has a substantial impact on reported PA levels though no 85 significant associations with CM risk were observed. Froude IC cut points represent a 86 promising approach towards classifying children’s PA data.