Validity of Wrist-Worn Activity Trackers for Estimating VO 2max and Energy Expenditure

Int J Environ Res Public Health. 2019 Aug 22;16(17):3037. doi: 10.3390/ijerph16173037.

Abstract

Activity trackers are a simple and mostly low-priced method to capture physiological parameters. Despite the high number of wrist-worn devices, there is a lack of scientific validation. The purpose of this study was to assess whether the activity trackers represent a valid alternative to gold-standard methods in terms of estimating energy expenditure (EE) and maximum oxygen uptake (VO2max). Twenty-four healthy subjects participated in this study. In total, five commercially available wrist-worn devices were tested with regard to their validity of EE and/or VO2max. Estimated values were compared with indirect calorimetry. Validity of the activity trackers was determined by paired sample t-tests, mean absolute percentage errors (MAPE), Intraclass Correlation Coefficient, and Bland-Altman plots. Within the tested devices, differences in scattering in VO2max and EE could be observed. This results in a MAPE > 10% for all evaluations, except for the VO2max-estimation of the Garmin Forerunner 920XT (7.3%). The latter significantly underestimates the VO2max (t(23) = -2.37, p = 0.027), whereas the Garmin Vivosmart HR significantly overestimates the EE (t(23) = 2.44, p = 0.023). The tested devices did not show valid results concerning the estimation of VO2max and EE. Hence, the current wrist-worn activity trackers are most likely not accurate enough to be used for neither purposes in sports, nor in health care applications.

Keywords: accuracy; consumer wearable devices; fitness trackers; monitoring; physical activity; sports watches; validation.

MeSH terms

  • Adult
  • Energy Metabolism*
  • Female
  • Fitness Trackers / statistics & numerical data*
  • Germany
  • Humans
  • Male
  • Oxygen Consumption*
  • Reproducibility of Results
  • Wrist
  • Young Adult