Validating hip- and wrist-ActiGraph accelerometer cut-points for physical activity intensities in people living with coronary heart disease

RESEARCH ARTICLE Validating hip- and wrist-ActiGraph accelerometer cut-points for physical activity intensities in people living with coronary heart disease Nicole Freene 1*, Brad Clark2, Maria Bäck3,4, Theo Niyonsenga 1, Kate Pumpa 2,5, Arjun Rangaraj6, Tze Hao Wong6, Soraya Joseph6, Ahmed Khan6, Rachel Davey1, Amanda Lönn1,7 1 Health Research Institute, University of Canberra, Canberra, Australia, 2 Research Institute for Sport and Exercise, University of Canberra, Canberra, Australia, 3 Department of Health, Medicine and Caring Sciences, Unit of Physiotherapy, Linköping University, Linköping, Sweden, 4 Department of Occupational Therapy and Physiotherapy, Sahlgrenska University Hospital, Gothenburg, Sweden, 5 Institute for Sport and Health, University College Dublin, Dublin, Ireland, 6 Canberra Health Services, Canberra, Australia, 7 Department of Physical Activity and Health, The Swedish School of Sport and Health Sciences, Gymnastik- Och Idrottshögskolan (GIH), Lidingövägen 1, Stockholm, Sweden * Abstract OPEN ACCESS Citation: Freene N, Clark B, Bäck M, Niyonsenga T, Pumpa K, Rangaraj A, et al. (2026) Validating hip- and wrist-ActiGraph accelerometer cut-points for physical activity intensities in people living with coronary heart disease. PLoS One 21(5): e0349618. https:// doi.org/10.1371/journal.pone.0349618 Editor: Yoshihiro Fukumoto, Kurume University School of Medicine, JAPAN Received: March 6, 2026 Accepted: May 1, 2026 Published: May 28, 2026 Copyright: © 2026 Freene et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data availability statement: There are ethical and legal restrictions on the public sharing of minimal data for this study. Data contain potentially identifiable and sensitive participant information. Data for this study are available upon request from the University of Canberra People with coronary heart disease (CHD) are encouraged to meet the public health moderate-to-vigorous aerobic physical activity (MVPA) guidelines for secondary prevention of cardiovascular disease. However, no accelerometer aerobic intensity cutpoints are currently available to classify MVPA in this population. This study aimed to establish absolute and relative aerobic physical activity intensity accelerometer cut-points in people with CHD and compare the new with existing cut-points in an international cohort. Eighty-six participants with CHD performed a restingmetabolic-rate (RMR) assessment, activities-of-daily-living (ADLs) and a peak treadmill test with mixed-chamber gas analysis while wearing two ActiGraph GT3X accelerometers (hip and wrist). The average RMR was 2.8 ml.kg-1.min-1, 20% less than the commonly used 1 Metabolic Equivalent of Task (3.5 ml.kg-1.min-1). The study sample was randomly split into a training and independent validation set (2:1) allowing for cross validation. In the training set, there were significant positive correlations between accelerometer counts.min-1 (y-axis, vector-magnitude (VM)) and intensity (relative and absolute) across both accelerometer hip- and wrist-placements for all activities (p < 0.001). Using Generalized Estimating Equation modelling, there was a strong linear relationship between accelerometer counts and absolute intensity for hip-placement (R2 = 0.62–0.71), and weaker relationships for hip relative intensity (R2 = 0.40–0.47) and wrist-placement (R2 = 0.09–0.25). In the validation set, BlandAltman plots found that the mean differences between predicted and actual absolute and relative intensity measures were negligible for all accelerometer counts.min-1 PLOS One | https://doi.org/10.1371/journal.pone.0349618 May 28, 2026 1 / 13 Human Research Ethics Committee via email () for researchers who meet the criteria for access to confidential data. Funding: Funding for this study was provided by an ActiGraph Digital Endpoint Accelerator Research (DEAR) Grant 2022 and a Critical Path Institute (C-Path) Grant received by NF. AL is supported by a Swedish Heart-Lung Foundation Post-doctoral Research Fellow (Abroad) Scholarship (nr. 20220860). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. (y-axis, VM) and placements (hip, wrist), although the dispersion of the differences (95% limits of agreement) were wide. Hip VM counts.min-1 cut-points were found to best identify absolute and relative MVPA. In the international comparison (n = 176), participants completed significantly more MVPA using the new cut-points (p < 0.001). Thus, accelerometer cut-points developed in healthy individuals appear to underestimate physical activity intensity in this population and cut-points specific to people with CHD should be used. Australian New Zealand Clinical Trials Registry: ACTRN12623000605695. Introduction One in three myocardial infarctions are repeat events [1]. Not only are repeat myocardial infarctions more likely to be fatal, they are costly [1]. People with coronary heart disease (CHD) are encouraged to meet the public health physical activity guidelines to prevent repeat events and premature death [2]. To determine whether guidelines are being met, accurate measurement of physical activity is essential. Accelerometry measures of physical activity have been found to be more reliable and valid compared with self-report measures [3,4]. However, despite advances in technology, categorisation of physical activity intensity using accelerometry still exist [5]. Currently, accelerometer cut-point equations used to categorise physical activity intensity in people with CHD have been based on studies with healthy adults [5]. Accurately measuring physical activity in clinical and older sub-groups is a challenge as some movements may be slow and difficult to capture. Additionally, small changes in physical activity may lead to important health effects in these groups [3]. An absolute intensity approach may also not be the most accurate when examining physical activity in different disease states and age groups, as maximal oxygen uptake and resting metabolic rate decreases with age and clinical conditions, such as CHD [6,7]. Accelerometer measured physical activity is reported as low within cardiac rehabilitation, with only 15% of participants with CHD meeting the physical activity guidelines [4,8]. It is currently unclear if cardiac rehabilitation participants with CHD are not meeting the physical activity guidelines or being inaccurately classified. Accelerometer anatomical placement may also impact accelerometer cut-point thresholds [9]. Therefore, our research question is, does the use of accelerometer cut-points developed in healthy individuals underestimate the intensity of physical acti (...truncated)