Table 4.
Validity of devices to criterion measure. Correlation of Fitbit Flex™ 1 and ActiGraph GT3X + to observed step count and percent agreement to observed step count for Fitbit Flex™ and ActiGraph GT3X+, calculated as Mean Absolute Percentage Error (MAPE).
| SPEED | OBSERVED STEP COUNT | FITBIT FLEX™ | ACTIGRAPH GT3X+ | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| km/h | Mean±SD | n | Mean±SD | n | r (p-value)* | n | MAPE (%) | ULOA (%) | LLOA (%) | Mean±SD | n | r (p-value)* | n | MAPE (%) | ULOA (%) | LLOA (%) |
| 8 | 318 ± 16 | 27 | 318 ± 16 | 27 | 0.997 (<0.001)1 | 25 | 0 | 1 | 0 | 318 ± 15 | 29 | 0.997 (<0.001)1 | 27 | 0 | 1 | 0 |
| 10 | 331 ± 21 | 26 | 331 ± 20 | 25 | 0.994 (<0.001)1 | 24 | 1 | 1 | -1 | 331 ± 20 | 27 | 0.998 (<0.001)1 | 26 | 0 | 1 | 0 |
| 12 | 342 ± 21 | 24 | 335 ± 30 | 23 | 0.829 (<0.001)1 | 22 | 1 | 7 | -5 | 338 ± 28 | 25 | 0.990 (<0.001)1 | 24 | 1 | 2 | -1 |
| 14 | 346 ± 23 | 10 | 347 ± 21 | 11 | 0.999 (<0.001)1 | 9 | 0 | 0 | 1 | 341 ± 19 | 13 | 0.905 (<0.001)1 | 10 | 1 | 6 | -4 |
| 16 | 356 ± 20 | 5 | 345 ± 27 | 6 | 0.409 (0.494) | 5 | 4 | 19 | -11 | 350 ± 19 | 6 | 0.762 (0.134) | 5 | 2 | 9 | -6 |
*
correlation to observed step count; km/h = kilometres per hour SD = +/- 1Standard deviation; n = number of participants; r = Pearson's r for parametric data; MAPE = Mean Absolute Percentage Error; ULOA = upper limit of agreement; LLOA = lower limit of agreement; 1Statistically significant at p < 0.05