Reference values for cut-point-free and traditional accelerometer metrics and associations with cardiorespiratory fitness: a cross-sectional study of healthy adults aged 20 to 89 years

ObjectivesTo compare the association between cardiorespiratory fitness (CRF) and cut-point-free accelerometer metrics (intensity gradient [IG] and average acceleration [AvAcc]) to that with traditional metrics in healthy adults aged 20 to 89 years and patients with heart failure, and 2) provide age-, sex-, and CRF-related reference values for healthy adults. MethodsIn the COmPLETE study, 463 healthy adults and 67 patients with heart failure wore GENEActiv accelerometers on their non-dominant wrist and underwent cardiopulmonary exercise testing. Cut-point-free (IG: distribution of intensity of activity across the day; AvAcc: proxy of volume of activity) and traditional (moderate-to-vigorous and vigorous activity) metrics were generated. The rawacceleration application was developed to translate findings into clinical practice. ResultsIG and AvAcc yield complementary information on PA with both IG (p=0.009) and AvAcc (p<0.001) independently associated with CRF in healthy individuals. Only IG was independently associated with CRF in patients with heart failure (p=0.043). The best cut-point-free and cut-point-based model had similar predictive value for CRF in both cohorts. However, unlike traditional metrics, IG and AvAcc are comparable across populations and the most commonly used accelerometers. We produced age- and sex-specific reference values and percentile curves for IG, AvAcc, moderate-to-vigorous, and vigorous activity for healthy adults. ConclusionsIG and AvAcc are strongly associated with CRF and, thus, indirectly with the risk of non-communicable diseases and mortality in healthy adults and patients with heart failure. Our reference values enhance the utility of cut-point-free metrics and facilitate their interpretation. Trial registrationThis study was registered on clinicaltrials.gov (NCT03986892). O_LIWhat is already known on this topic - Cut-point free accelerometer metrics are valuable to assess physical activity because of their comparability across populations and association with various health parameters (e.g. body fat content or physical functioning). Yet, their interpretation is not straightforward. C_LIO_LIWhat this study adds - This study found a strong and independent association of cut-point-free metrics with cardiorespiratory fitness, a vital sign, in healthy individuals aged between 20 to 89 years and patients with heart failure. We produced the first reference values based on healthy individuals across the age span. C_LIO_LIHow this study might affect research, practice or policy - Our reference values together with the new open-source application may simplify the interpretation of cut-point-free accelerometer metrics and their use in clinical practice and research. C_LI