Introduction: To capitalize on the increasing availability of accelerometry data for epidemiological research it is desirable to compare and/or pool data from surveys worldwide. This study aimed to establish whether free-living physical activity outcomes can be considered equivalent between three research-grade accelerometer brands worn on the dominant and non-dominant wrist. Of prime interest were the average acceleration (ACC) and the intensity gradient (IG). These two metrics describe the volume and intensity of the complete activity profile; further, they are comparable across populations making them ideal for comparing and/or pooling activity data. Methods: Forty-eight adults wore a GENEActiv, Axivity, and ActiGraph on both wrists for up to 7-days. Data were processed using open-source software (GGIR) to generate physical activity outcomes, including ACC and IG. Agreement was assessed using pairwise 95% equivalence tests (±10% equivalence zone) and intra-class correlation coefficients (ICC). Results: ACC was equivalent between brands when measured at the non-dominant wrist (ICC ≥ 0.93), but approximately 10% higher when measured at the dominant wrist (GENEActiv and Axivity only, ICC ≥ 0.83). The IG was equivalent irrespective of monitor brand or wrist (ICC ≥ 0.88). After adjusting ACC measured at the dominant wrist by −10% (GENEActiv and Axivity only), ACC was also within (or marginally outside) the 10% equivalence zone for all monitor pairings. Conclusion: If average acceleration is decreased by 10% for studies deploying monitors on the dominant wrist (GENEActiv and Axivity only), ACC and IG may be suitable for comparing and/or collating physical activity outcomes across accelerometer datasets, regardless of monitor brand and wrist.
Rowlands, Plekhanova, Yates, Davies, Khunti, and Edwardson are with the Diabetes Research Centre, Leicester General Hospital, University of Leicester, Leicester, United Kingdom; and the NIHR Leicester Biomedical Research Centre, Leicester, United Kingdom. Rowlands is with the Division of Health Sciences, Alliance for Research in Exercise, Nutrition, and Activity (ARENA), Sansom Institute for Health Research, University of South Australia, Adelaide, Australia. Mirkes is with the Department of Mathematics, University of Leicester, United Kingdom. Rowlands, Plekhanova, Yates, Davies, Khunti, and Edwardson are also with the Leicester Diabetes Centre, University Hospitals of Leicester, Leicester, United Kingdom. Khunti is also with the NIHR Collaboration for Leadership in Applied Health Research and Care East Midlands, Leicester General Hospital, United Kingdom.