ORIGINAL ARTICLE  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2021 February;61(2):205-11

DOI: 10.23736/S0022-4707.20.11151-4

Copyright © 2020 EDIZIONI MINERVA MEDICA

language: English

The accuracy of fitness watches for the measurement of heart rate and energy expenditure during moderate intensity exercise

Andrew R. JAGIM ^{1, 2} ✉, Nicolas KOCH-GALLUP ³, Clayton L. CAMIC ⁴, Leah KROENING ², Charles NOLTE ¹, Cassidy SCHROEDER ², Lindsay GRAN ¹, Jacob L. ERICKSON ¹

¹ Sports Medicine, Mayo Clinic Health System, Onalaska, WI, USA; ² Exercise and Sport Science Department, University of Wisconsin La Crosse, La Crosse, WI, USA; ³ Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, USA; ⁴ Kinesiology and Physical Education, Northern Illinois University, DeKalb, IL, USA

BACKGROUND: As new technology emerges and updated fitness watches are released to the market, it is important to examine their accuracy. The aim of the current study was to examine the accuracy of three commercially available activity trackers in assessing heart rate (HR) and energy expenditure (EE) during moderate intensity exercise.
METHODS: Twenty healthy participants (Age: 20.5±0.7 yrs., Ht: 173.4±10.8 cm, BM: 72.8±13.9 kg, BMI: 24.0±2.5 kg/m²) wore two fitness watches (FB: Fitbit Versa^TM, San Francisco, CA, USA; and PI: Polar Ignite^TM, Polar Electro Oy, Kempele, Finland) and a chest-worn HR monitor (PTP: Polar TeamPro Sensor^TM, Polar Electro) during a 12-minute exercise protocol at incremental speeds. An electrocardiogram (ECG) and indirect calorimetry were used as criterion measures for HR and EE. Mean absolute percentage error (MAPE) was calculated to determine measurement error.
RESULTS: The MAPE values for HR were 11.6±8.7% for the FB, 11.0±10.0% for the PI, and 6.3±5.2% for the PTP. For EE, MAPE values were 9.6±7.2% for the FB, 16.7±19.6% for the PI and 13.8±13.0% for the PTP.
CONCLUSIONS: Fitness watches relying on optical measures of HR underestimate HR compared to criterion measures during moderate intensity exercise. Despite providing a more accurate measure of HR, a chest-worn monitor does not provide a more accurate estimate of EE compared to fitness watches. The Fitbit provided the most accurate measure of EE when compared to the Polar Ignite watch and chest-worn device.

KEY WORDS: Fitness trackers; Heart rate; Energy metabolism