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Accelerometer-assessed Physical Activity in Epidemiology: Are Monitors Equivalent?

Rowlands, Alex V; Mirkes, Evgeny M; Yates, Tom; Clemes, Stacey; Davies, Melanie; Khunti, Kamlesh; Edwardson, Charlotte L
Medicine & Science in Sports & Exercise: Post Acceptance: October 02, 2017
doi: 10.1249/MSS.0000000000001435
Original Investigation: PDF Only


Accelerometers are increasingly being used to assess physical activity in large-scale surveys. Establishing whether key physical activity outcomes can be considered equivalent between three widely-used accelerometer brands would be a significant step towards capitalising on the increasing availability of accelerometry data for epidemiological research.


Twenty participants wore a GENEActiv, Axivity AX3 and ActiGraph GT9X on their non-dominant wrist and were observed for two-hours in a simulated living space. Participants undertook a series of seated and upright light/active behaviours at their own pace. All accelerometer data were processed identically using open-source software (GGIR) to generate physical activity outcomes (including average dynamic acceleration (ACC) and time within intensity cut-points). Data were analysed using pairwise 95% equivalence tests (±10% equivalence zone), intra-class correlation coefficients (ICC) and limits of agreement.


The GENEActiv and Axivity could be considered equivalent for ACC (ICC=0.95, 95% confidence interval (CI) 0.87 to 0.98), but ACC measured by the ActiGraph was approximately 10% lower (ICC: GENEActiv/ActiGraph 0.86, 95% CI 0.56 to 0.95; Axivity/ActiGraph 0.82, 95% CI 0.50 to 0.94). For time spent within intensity cut-points, all three accelerometers could be considered equivalent to each other for over 85% of outcomes (ICC≥0.69, lower 95% CI≥0.36), with the GENEActiv and Axivity equivalent for 100% of outcomes (ICC≥0.95, lower 95% CI≥0.86).


GENEActiv and Axivity data processed in GGIR are largely equivalent. If comparing GENEActiv or Axivity to the ActiGraph, time spent within intensity cut-points has good agreement. These findings can be used to inform selection of appropriate outcomes if comparing outputs from these accelerometer brands.

Corresponding author: Alex Rowlands, Diabetes Research Centre, University of Leicester, Leicester General Hospital, Leicester, LE5 4PW, UK. Tel: +44 116 258 8595

The research was supported by the National Institute for Health Research (NIHR) Biomedical Research Centre 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 are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health. No external sources of funding were accessed. The results of the present study do not constitute endorsement by ACSM. We declare that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation.

Accepted for Publication: 22 September 2017

© 2017 American College of Sports Medicine