Intensity Thresholds on Raw Acceleration Data: Euclidean Norm Minus One (ENMO) and Mean Amplitude Deviation (MAD) Approaches

PLOS ONE, Dec 2019

Objectives (1) To develop and internally-validate Euclidean Norm Minus One (ENMO) and Mean Amplitude Deviation (MAD) thresholds for separating sedentary behaviours from common light-intensity physical activities using raw acceleration data collected from both hip- and wrist-worn tri-axial accelerometers; and (2) to compare and evaluate the performances between the ENMO and MAD metrics. Methods Thirty-three adults [mean age (standard deviation (SD)) = 27.4 (5.9) years; mean BMI (SD) = 23.9 (3.7) kg/m2; 20 females (60.6%)] wore four accelerometers; an ActiGraph GT3X+ and a GENEActiv on the right hip; and an ActiGraph GT3X+ and a GENEActiv on the non-dominant wrist. Under laboratory-conditions, participants performed 16 different activities (11 sedentary behaviours and 5 light-intensity physical activities) for 5 minutes each. ENMO and MAD were computed from the raw acceleration data, and logistic regression and receiver-operating-characteristic (ROC) analyses were implemented to derive thresholds for activity discrimination. Areas under ROC curves (AUROC) were calculated to summarise performances and thresholds were assessed via executing leave-one-out-cross-validations. Results For both hip and wrist monitor placements, in comparison to the ActiGraph GT3X+ monitors, the ENMO and MAD values derived from the GENEActiv devices were observed to be slightly higher, particularly for the lower-intensity activities. Monitor-specific hip and wrist ENMO and MAD thresholds showed excellent ability for separating sedentary behaviours from motion-based light-intensity physical activities (in general, AUROCs >0.95), with validation indicating robustness. However, poor classification was experienced when attempting to isolate standing still from sedentary behaviours (in general, AUROCs <0.65). The ENMO and MAD metrics tended to perform similarly across activities and accelerometer brands. Conclusions Researchers can utilise these robust monitor-specific hip and wrist ENMO and MAD thresholds, in order to accurately separate sedentary behaviours from common motion-based light-intensity physical activities. However, caution should be taken if isolating sedentary behaviours from standing is of particular interest.

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Intensity Thresholds on Raw Acceleration Data: Euclidean Norm Minus One (ENMO) and Mean Amplitude Deviation (MAD) Approaches

October Intensity Thresholds on Raw Acceleration Data: Euclidean Norm Minus One (ENMO) and Mean Amplitude Deviation (MAD) Approaches Kishan Bakrania 0 1 Thomas Yates 1 Alex V. Rowlands 1 Dale W. Esliger 1 Sarah Bunnewell 1 James Sanders 1 Melanie Davies 1 Kamlesh Khunti 1 Charlotte L. Edwardson 1 0 Department of Health Sciences, University of Leicester, Leicester General Hospital , Leicester, Leicestershire , United Kingdom , 2 Diabetes Research Centre, University of Leicester, Leicester General Hospital , Leicester, Leicestershire , United Kingdom , 3 National Institute for Health Research (NIHR) Leicester-Loughborough Diet, Lifestyle and Physical Activity Biomedical Research Unit (BRU), Diabetes Research Centre, Leicester General Hospital , Leicester, Leicestershire , United Kingdom , 4 Alliance for Research in Exercise, Nutrition and Activity (ARENA), Sansom Institute for Health Research, Division of Health Sciences, University of South Australia , Adelaide , Australia , 5 School of Sport, Exercise and Health Sciences, Loughborough University , Loughborough, Leicestershire , United Kingdom , 6 National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care ± East Midlands (CLAHRC ± EM), Diabetes Research Centre, Leicester General Hospital , Leicester, Leicestershire , United Kingdom 1 Editor: Maciej Buchowski, Vanderbilt University , UNITED STATES - OPEN ACCESS Data Availability Statement: All data underlying the findings of this study are included in the following file: Supporting Information - S1 File. Funding: The research was supported by the National Institute for Health Research (NIHR) Diet, Lifestyle & Physical Activity Biomedical Research Unit (BRU) based at University Hospitals of Leicester and Loughborough University, the National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care ± East Midlands (NIHR CLAHRC ± EM) and the Leicester Clinical Trials Unit. The views expressed Objectives (1) To develop and internally-validate Euclidean Norm Minus One (ENMO) and Mean Amplitude Deviation (MAD) thresholds for separating sedentary behaviours from common light-intensity physical activities using raw acceleration data collected from both hip- and wrist-worn tri-axial accelerometers; and (2) to compare and evaluate the performances between the ENMO and MAD metrics. Methods Thirty-three adults [mean age (standard deviation (SD)) = 27.4 (5.9) years; mean BMI (SD) = 23.9 (3.7) kg/m2; 20 females (60.6%)] wore four accelerometers; an ActiGraph GT3X+ and a GENEActiv on the right hip; and an ActiGraph GT3X+ and a GENEActiv on the nondominant wrist. Under laboratory-conditions, participants performed 16 different activities (11 sedentary behaviours and 5 light-intensity physical activities) for 5 minutes each. ENMO and MAD were computed from the raw acceleration data, and logistic regression and receiver-operating-characteristic (ROC) analyses were implemented to derive thresholds for activity discrimination. Areas under ROC curves (AUROC) were calculated to summarise performances and thresholds were assessed via executing leave-one-out-crossvalidations. are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health. Competing Interests: The authors have declared that no competing interests exist. Results For both hip and wrist monitor placements, in comparison to the ActiGraph GT3X+ moni tors, the ENMO and MAD values derived from the GENEActiv devices were observed to be slightly higher, particularly for the lower-intensity activities. Monitor-specific hip and wrist ENMO and MAD thresholds showed excellent ability for separating sedentary behaviours from motion-based light-intensity physical activities (in general, AUROCs >0.95), with validation indicating robustness. However, poor classification was experienced when attempting to isolate standing still from sedentary behaviours (in general, AUROCs <0.65). The ENMO and MAD metrics tended to perform similarly across activities and accelerometer brands. Conclusions Researchers can utilise these robust monitor-specific hip and wrist ENMO and MAD thresholds, in order to accurately separate sedentary behaviours from common motion-based light-intensity physical activities. However, caution should be taken if isolating sedentary behaviours from standing is of particular interest. Introduction There is cumulative evidence that sedentary behaviour, characterised as any waking behaviour with low energy expenditure ( 1.5 metabolic equivalents) while in a sitting or reclining posture [ 1 ], is detrimentally associated with a number of health outcomes including cardiovascular disease, type 2 diabetes mellitus and all-cause mortality [ 2–7 ]. This has important implications given that adults spend the majority of their waking hours (~55% to ~70%) sedentary [ 8–11 ]. Correspondingly, engaging in light-intensity physical (...truncated)


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Kishan Bakrania, Thomas Yates, Alex V. Rowlands, Dale W. Esliger, Sarah Bunnewell, James Sanders, Melanie Davies, Kamlesh Khunti, Charlotte L. Edwardson. Intensity Thresholds on Raw Acceleration Data: Euclidean Norm Minus One (ENMO) and Mean Amplitude Deviation (MAD) Approaches, PLOS ONE, 2016, Volume 11, Issue 10, DOI: 10.1371/journal.pone.0164045