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Activity intensity, volume, and norms: Utility and interpretation of accelerometer metrics
journal contributionposted on 29.10.2019 by Alex V. Rowlands, Stuart J. Fairclough, Tom Yates, Charlotte L. Edwardson, Melanie Davies, Fehmidah Munir, Kamlesh Khunti, Vicky H. Stiles
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PURPOSE: The physical activity profile can be described from accelerometer data using two population-independent metrics: average acceleration (ACC, volume) and intensity gradient (IG, intensity). This article aims 1) to demonstrate how these metrics can be used to investigate the relative contributions of volume and intensity of physical activity for a range of health markers across data sets and 2) to illustrate the future potential of the metrics for generation of age and sex-specific percentile norms. METHODS: Secondary data analyses were conducted on five diverse data sets using wrist-worn accelerometers (ActiGraph/GENEActiv/Axivity): children (n = 145), adolescent girls (n = 1669), office workers (n = 114), premenopausal (n = 1218) and postmenopausal (n = 1316) women, and adults with type 2 diabetes (n = 475). Open-source software (GGIR) was used to generate ACC and IG. Health markers were (a) zBMI (children), (b) út (adolescent girls and adults), (c) bone health (pre- and postmenopausal women), and (d) physical function (adults with type 2 diabetes). RESULTS: Multiple regression analyses showed that IG, but not ACC, was independently associated with zBMI/út in children and adolescents. In adults, associations were stronger and the effects of ACC and IG were additive. For bone health and physical function, interactions showed associations were strongest if IG was high, largely irrespective of ACC. Exemplar illustrative percentile "norms" showed the expected age-related decline in physical activity, with greater drops in IG across age than ACC. CONCLUSION: The ACC and the IG accelerometer metrics facilitate the investigation of whether volume and intensity of physical activity have independent, additive, or interactive effects on health markers. In future studies, the adoption of data-driven metrics would facilitate the generation of age- and sex-specific norms that would be beneficial to researchers.
The ASSK physical activity intervention study was funded by West Lancashire Sport Partnership UK, West Lancashire Community Leisure UK, and Edge Hill University Ormskirk UK. The Girls Active evaluation was funded by the NIHR Public Health Research Programme (13/90/30) and undertaken in collaboration with the Leicester Clinical Trials Unit, a UKCRC-registered clinical trial unit in receipt of NIHR CTU support funding. The SMArT Work trial was funded by the Department of Health Policy Research Programme (project no. PR-R5-0213-25004). The processing and analysis of the Biobank pre- and postmenopausal data work was supported by an internal grant from the University of Exeter (UK) Project Development Fund (Science). Professors Davies and Khunti are NIHR Senior Investigators. University of Leicester authors are supported by the NIHR Leicester Biomedical Research Centre, and the Collaboration for leadership in Applied Health Research and Care (CLAHRC) East Midlands.
- Sport, Exercise and Health Sciences