Is this Bit Fit? Measuring the Quality of the Fitbit Step-Counter

Abstract

Background: Accurate measurement of physical activity is essential for understanding the relationship between physical activity (PA) and health outcomes. Technological advances have led to a surge in commercially-available pedometers, however, limited scientific evidence exists regarding their accuracy Purpose: This study is the first to test the quality of the newly developed Fitbit step-counter and comparability relative to the Yamax SW-200 pedometer. Methods: Ten healthy young adults participated. The quality of the Fitbit was assessed through: 1) a 20 Step Test; 2) a motor vehicle test; and 3) a treadmill test at various speeds (2, 3, 4, 5, 6, 8, 9, 10, 11 kmh-1) on three locations on the body (inside pocket, waist, upper body). Results: The 20 Step Test revealed that none of the Fitbits had error scores greater than +/- 5% and during the motor vehicle condition, the Fitbits did not record any spurious movement. Statistical differences were found between the observed steps and detected steps for Yamax at walking speeds of 2 kmh-1 (p < 0.001) and 3 kmh-1 (p < 0.05), as well as the waist-mounted Fitbit at 2 kmh-1 (p < 0.05). All locations of the Fitbit and the Yamax were very accurate at normal walking speeds of 4.5 kmh-1 and 6.0 kmh-1. In terms of running speeds (8 kmh-1, 9 kmh-1, 10 kmh-1, 11 kmh-1) there were only significant differences found between observed steps and detected steps for the Fitbit in the pocket. Conclusions: Our quality-control testing should now enable physical activity practitioners, consumers and researchers alike to make a more informed decision on whether to purchase and utilize the FitBit.