Assessment of Accuracy of Overall Energy Expenditure Measurements for the Fitbit Charge HR 2 and Apple Watch

Objectives: In this study, we sought to determine the accuracy of energy expenditure (EE) esti- mation for the Fitbit Charge HR 2 (Fitbit) and the Apple Watch. Design: An observational study. Methods: Thirty young adults (15 men and 15 women, aged 23.5 ± 2.96 years) completed the Bruce treadmill protocol. We measured gross EE by a PARVO metabolic cart (MetCart) and concurrently estimated by the Fitbit and Apple Watch. We calculated concordance correlation coefficients (CCC, r c ) and relative error rates to indicate the difference between each device and the MetCart system. Results: For the Apple Watch and Fitbit, the relative error rate was 24.3%, 20.1% for the pooled sample, 18.6%, 24.2% for men, and 29.9%, 16.7% for women, respectively. The Apple Watch overestimated EE for women and underestimated EE for men; the Fitbit underestimated EE for both. Moderate CCCs between estimated EEs and MetCart measured EEs were found for both Apple Watch (r c =0.65, 0.43, and 0.39 overall, men and women, respectively) and Fitbit (r c =0.53, 0.39, and 0.21 overall, men and women, respectively). Conclusion: Neither device showed accurate results compared with EE measured by a MetCart. Users should consider these results when designing programs or personal training plans where physical activity EE is a key outcome assessed with a wearable device

Cart · Concordance · Energy expenditure · Observational study · Physical activity · Physical therapy · Treadmill · Children's Physical and Motor Development · Engineering · Medicine · Physical Activity and Health · Internal Medicine