Nuss, Kayla, authorThomson, Elizabeth, authorComstock, Ashley, authorReinwald, Steven, authorBlake, Sophie, authorPimentel, Richard, authorTracy, Brian, authorLi, Kaigang, author2017-11-132017-11-132017https://hdl.handle.net/10217/184855Background: This study assessed the validity of heart rate (HR) and energy expenditure (EE) measurements for the Fitbit Charge and Apple Watch. Methods: Thirty young adults (15 females, 15 males, age 23.5±3.0) completed the Bruce Protocol. HR measurements were recorded from the electrocardiogram (ECG) and each device every minute. EE measurements were recorded from the devices at the conclusion of exercise and calculated from the PARVO data. Results: For heart rate, the Apple Watch showed lower RER (2.4%-5.1%) compared with the Fitbit (3.9%-13.5%) for all exercise intensities. For both devices, the strongest relationship with ECG-measured HR was found for very light PA with very high CCC (rc>.90). The strength of the relationship declined with increases in exercise intensity for Apple Watch and Fitbit. For energy expenditure, the Apple Watch relative error was 24.25% for overall, 18.58% for males, and 29.93% for females. For the Fitbit, the relative error was 20.07% for overall, 24.17% for males, and 16.72% for females. Conclusions: Both the Fitbit Charge and the Apple Watch are inaccurate when measuring heart rate and energy expenditure. These results indicate a need for the consumer to use them with caution.born digitalStudent workspostersengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.Apple watchFitbitenergy expenditureheart rate validityaccuracyenergy balanceText