Abstract MP11: Fitbit: An Accurate and Reliable Device for Wireless Physical Activity Tracking
Background: A smart accelerometer named the Fitbit has recently been introduced in the consumer market as a physical activity monitor that can interface wirelessly with mobile phones and a manufacturer-established website to allow consumers to track their physical activity in real-time. The purpose of this study was to examine the validity and reliability of the Fitbit for measuring energy expenditure during treadmill walking and running relative to energy expenditure assessed by indirect calorimetry. Methods: A total of 23 healthy adults (10 males, mean age: 30.6 ± 7.9 years; mean BMI: 24.7 ± 3.0 kg/m2) completed a four-phase treadmill exercise protocol (6 min/phase) under laboratory conditions. The protocol consisted of walking at slow (1.9 mph), moderate (3.0 mph), and brisk (4.0 mph) paces; and jogging (5.2 mph). Participants were fitted with three hip-based Fitbit One devices (two on right, one on left hip) and two wrist-based Fitbit Flex devices (one on right and left wrist). Energy expenditure was measured by gas exchange indirect calorimetry. Results: The mean difference of Fitbit-estimated energy expenditure from measured energy expenditure ranged from -0.8 to 0.4 kcals and -0.2 to 2.6 kcals for the hip- and wrist-based Fitbit devices, respectively (see Table). The greatest differences were seen in the wrist-based Fitbit during moderate and brisk walking. Across all phases, the within-participant correlation of Fitbit-estimated energy expenditure to measured energy expenditure was 0.86 to 0.87 for all hip devices (two on right, one on left hip) and 0.88 for both wrist devices (left and right wrists). The inter-device correlation between Fitbit-estimated energy expenditure of the right hip devices was 0.96, between right (front-most) and left hip devices was 0.97, and between right and left wrist devices was 0.95. Conclusions: These results suggest that the Fitbit One and Fitbit Flex physical activity monitors are valid and reliable devices for measuring energy expenditure during physical activity.
Author Disclosures: K.M. Diaz: None. D.J. Krupka: None. M.J. Chang: None. Y. Ma: None. J. Goldsmith: None. J.E. Schwartz: None. K.W. Davidson: None.
- © 2015 by American Heart Association, Inc.