Garmin Fénix 7^® Underestimates Performance at the Lactate Threshold in Comparison to Standardized Blood Lactate Field Test

Abstract

Purpose

Lactate threshold (LT) is a critical performance measure traditionally obtained using costly laboratory-based tests. Wearables offer a practical and noninvasive alternative for LT assessment in recreational and professional athletes. However, the comparability of these estimates with the regular field tests requires further evaluation.

Patients and Methods

In our sample of 26 participants (n_f=7 and n_m=19), we compared the estimated running pace and heart rate (HR) at LT with two subsequent tests. First, participants performed the Fenix 7^® threshold running test after a calibration phase. Subsequently, they were tested in a standardized, graded blood lactate field test. Age was 25.97 (± 6.26) years, and body mass index (BMI) was 24.58 (± 2.8) kg/m².

Results

Pace at LT calculated by Fenix 7^® (M=11.87 km/h ± 1.26 km/h) was 11.96% lower compared to the field test (M=13.28 km/h ± 1.72 km/h), which was significant (p <0.001, d=−1.19). HR estimated by the Fenix 7^® at LT was 1.71% lower (p >0.05). LT data obtained in the field test showed greater overall variance.

Conclusion

Our results suggest sufficient accuracy of Fenix 7^® LT estimates for recreational athletes. It can be assumed that for professional athletes, it would fail to provide the nuanced data needed for high-quality training management.

Keywords:

• smartwatch
• physical performance
• physiology
• heart rate
• pace

Institutional Review Board Statement

The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board of the University of Bundeswehr Munich (protocol code EK UniBw M 23-28 on 18^th of May 2023) for studies involving humans.

Informed Consent Statement

Informed consent was obtained from all the subjects involved in the study.

Data Sharing Statement

All anonymized data are available upon request.

Acknowledgments

We would like to thank all subjects for their participation.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors declare no conflicts of interest in this work.

Additional information

Funding

This research and the associated Smart Health Lab (SHL) project were funded by the Center for Digitization and Technology Research of the German Bundeswehr. Dtec.bw is funded by the European Union, NextGenerationEU. We acknowledge financial support for open-access publishing by Universität der Bundeswehr München / dtec.bw.