“…More problematic still is the ongoing scientific debate over various technical issues related to accelerometry, such as appropriate choice of manufacturer and model, epoch length, inclusion criteria for what constitutes a valid file, and ultimately what accelerometry count cut-points offer meaningful interpretation and information on PA. 61 In contrast, the feasibility and reliability of standardized large scale and school-based fitness assessment by teachers or other trained individuals is well documented in the UK and internationally. 3,24,62,63 Importantly, while fitness and PA are independently associated with health, 12,64 studies in adults 65 and children 54 suggest that fitness is more strongly associated with cardio-metabolic risk than is PA. Given these health-associations, we argue that any cross-sectional, longitudinal or secular assessments of youth health should include a measure of CRF as well as at least 1 component of muscular fitness.…”