Accuracy and Reliability of Commercial Wrist-Worn Pulse Oximeter During Normobaric Hypoxia Exposure Under Resting Conditions

Res Q Exerc Sport. 2021 Sep;92(3):549-558. doi: 10.1080/02701367.2020.1759768. Epub 2020 Jul 7.


Purpose: The present study analyzed peripheral blood oxygen saturation (SpO2) and heart rate (HR) measurements taken on the Garmin fēnix® 5X Plus watch, comparing them to measurements taken on a standard medical-grade pulse oximeter during normobaric hypoxia exposure under resting conditions. Methods: Thirteen women (mean ± SD: Age 20 ± 1 years, height 165 ± 5 cm, mass, 67 ± 9 kg) and ten men (mean ± SD: Age 21 ± 3 years, height 177 ± 6 cm, mass 78 ± 11 kg) sat inside a customized environmental chamber while the fraction of inspired oxygen (FIO2) was adjusted to simulate altitudes of 12,000; 10,000; 8,000; 6,000; and 900 ft. The novel commercial device (Garmin fēnix®) and a medical-grade pulse oximeter (Nonin® 7500) were used to measure SpO2 and HR in triplicate at each simulated altitude. Bland-Altman analyses were used to assess differences between methods. Results: Bland-Altman analysis indicated 3.3% bias for SpO2 measurements taken on the Garmin fēnix® at 12,000 ft of simulated altitude (limits of agreement: -1.9-8.6%). Mean differences in SpO2 measurements were smaller at the remaining simulated altitudes, where bias measurements ranged from 0.7% to 0.8%. The Garmin fēnix® also underestimated heart rate, but those discrepancies were minimal (bias measurements at all simulated altitude exposures were < 1.0 bpm). Conclusions: With the exception of readings taken at 12,000 ft of simulated altitude, the Garmin fēnix® exhibits minimal overestimation of SpO2 and minimal underestimation of HR during simulated altitude exposure. These data suggest the Garmin fēnix® watch may be a viable method to monitor SpO2 and HR under most ambient environmental conditions.

Keywords: Altitude; athletics; track and field; wearable technology.

MeSH terms

  • Adolescent
  • Adult
  • Altitude Sickness / blood*
  • Female
  • Heart Rate / physiology*
  • Humans
  • Male
  • Oximetry / standards*
  • Oxygen / blood*
  • Reproducibility of Results
  • Wearable Electronic Devices / standards*
  • Wrist*
  • Young Adult


  • Oxygen