Fig. 6

Effect of age on overall accuracy (mean absolute percentage error, MAPE) of wearable technologies’ step counting ability. MAPE and corresponding 95% confidence intervals (CIs; estimated using mixed effect models) of each age group are presented at slow, normal, and fast walking speeds. MAPE values were averaged across devices respective to each age group for slow, normal, and fast walking speeds. Slow speed bouts: 0.8, 1.6, 2.4, 3.2 km/h (0.5, 1.0, 1.5, 2.0 mph); normal speed bouts: 4.0, 4.8, 5.6, 6.4 km/h (2.5, 3.0, 3.5, 4.0 mph); fast speed bouts: 7.2, 8.0 km/h (4.5, 5.0 mph). MAPE values closer to 0 represent greater accuracy. The 95% CIs bars were not drawn when they were shorter than the height of the symbol. Further, where 95% CIs do not overlap, there are significant differences between locations. Likelihood ratio test P value is reported for the effect of age on MAPE for each specific speed level. 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