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. 2022 Sep 8;19:117. doi: 10.1186/s12966-022-01350-9

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© The Author(s) 2022

Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

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Fig. 3 — Mean absolute percentage error (MAPE) across walking speeds presented by age group. Participants walked on a treadmill for 5-min bouts beginning at 0.8 km/h (0.5 mph) and increasing in 0.8 km/h (0.5 mph). MAPE (%) was computed for each person bout subtracting the directly observed steps (criterion measurement) from the wearable technology-derived steps and dividing it in absolute value by the directly observed steps. Black dots represent the averaged MAPE across specific age group for a given speed. Bars represent standard deviation of MAPE. The standard deviation bars were not drawn when they were shorter than the height of the symbol. Lower MAPE values indicate higher age group accuracy. All age groups (21–85 years) wore the Actical (N = 250), ActiGraph GT9X (Waist) (N = 254), ActiGraph GT9X (Wrist) (N = 254), activPAL (N = 249), Digi-Walker SW-200 (N = 258), GENEActiv (Waist) (N = 224), GENEActiv (Wrist) (N = 217), NL-1000 (N = 258), and the StepWatch (N = 253). Young Adults (21–40 years) also wore the Fitbit One (N = 80) and Garmin vivofit 2 (N = 80). Middle-Age Adults (41–60 years) also wore the Apple Watch Series 1 (N = 76), Fitbit One (N = 80), Garmin vivoactive HR (N = 77), Garmin vivofit 3 (N = 77), and the Samsung Gear Fit2 (N = 80). Older Adults (61–85 years) also wore the AppleWatch Series 1 (N = 98), Fitbit Ionic (N = 98), Fitbit Zip (N = 98), Garmin vivoactive 3 (N = 96), PiezoRx (N = 98), Polar M600 (N = 97), and the Samsung Gear Fit2 Pro (N = 98). See Additional file 2 for a graphical classification of wearable technologies by age groups. See Additional File 8: Suppl Table 2 for a tabular description of validity indices by age groups