9/18/2023 0 Comments Fitbit versions explained![]() ![]() ![]() As the technical details of Fitbit devices are unknown, continuous confirmation of the validity of new versions of the activity trackers is required. Fewer studies have looked at PA levels with reports of both under- and overestimations against a hip-worn research grade device and likewise varying results have been reported on energy expenditure (EE) against research grade devices at different placements. Of the studies testing the validity of wrist-worn Fitbit devices in a free-living setting, the majority have investigated the agreement on step count against a hip-worn research grade accelerometer, where mostly an overestimation by Fitbits was found. Furthermore, most studies have tested the validity of Fitbit devices on normal weight and young adults while few studies have been conducted in older or overweight populations. ĭespite the numerous studies investigating the validity of Fitbit devices in a laboratory setting, less research has been done in a free-living environment, although agreement has been shown to vary considerably between laboratory and free-living studies, probably because of the larger variation in activities under free-living conditions. However, the algorithms and technical details are proprietary limiting the potential to understand the errors and uncertainty associated with the commercial activity trackers. In 2017, a total of 115.4 million units were sold, with Fitbit being one of the dominating vendors with a market share of 15.4%. Furthermore, they have been found to be useful as intervention tools, and the development of wrist-worn accelerometers have the opportunity to increase compliance. Commercial accelerometers have also recently gained popularity, owing to the development of low-cost devices and cloud storage capacity, which provides opportunities for surveillance of people in real time. One of the most popular devices for use in research is the ActiGraph, which is often used as the comparison when testing newer devices. Historically, research into the benefits and consequences of PA rely on self-reported data, which are prone to inaccuracy and misclassification, but the development of accelerometers has provided opportunities for passive, direct monitoring of habitual PA in large populations over a long period as well as reducing the burden on participants. To research patterns of physical activity (PA) it is important to have methods that measure activity accurately. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. The Parker Institute is supported by a core grant from the Oak Foundation (grant agreement number: OCAY-18-774-OFIL). The application procedure can be obtained from the Research Unit for Dietary Studies at The Parker Institute ( or from the NoHoW data controller Graham Horgan ( The NoHoW study has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. Data used in the current study will be made available upon request after application to the NoHoW data controller. The restrictions are imposed by The Danish Data Protection Agency ( ). 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.ĭata Availability: There are legal restrictions on sharing data that contain potentially identifying or sensitive person information. Received: SeptemAccepted: Published: June 11, 2020Ĭopyright: © 2020 Mikkelsen et al. PLoS ONE 15(6):Įditor: Patrick Bergman, Linneaus University, SWEDEN (2020) Estimating physical activity and sedentary behaviour in a free-living environment: A comparative study between Fitbit Charge 2 and Actigraph GT3X. Citation: Mikkelsen M-LK, Berg-Beckhoff G, Frederiksen P, Horgan G, O’Driscoll R, Palmeira AL, et al. ![]()
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