KnowYourPrime Evidence Registry · Finding KYP-ER-0011

Wearable VO2 Max Estimate Accuracy

Question assessedAre smartwatch VO2 max estimates accurate against a laboratory treadmill or cycle test?

KnowYourPrime evidence ratingEmergingEvidence currently favors the claim, but more confirmation is needed.

On average across a group they come reasonably close, but for an individual they can be far off. Apple Watch estimates ran low in two validation studies, a Google Pixel Watch was close on average with wide individual error, and one Garmin model passed its test.

Finding KYP-ER-0011Version 1.0Reviewed October 24, 2026Rating rule 1.4CC BY 4.0

Why this is rated Emerging

A watch estimates VO2 max from heart rate during walks or runs, with no breath analysis. That makes group averages workable and individual readings noisy.

One Garmin validation affirms acceptable agreement. Four other anchor studies, two of Apple Watch, one of Google Pixel Watch and one of several trackers, found errors above 10 percent or wide individual limits. One clean anchor with several non-affirming ones puts the claim at Emerging: some evidence favors it, and more confirmation is needed.

How the rating rule reads this evidence

Anchor-grade evidence affirms the core relationship.
Multiple supporting studies are consistent with the core relationship.
An anchor study is present but its own reported finding does not cleanly affirm this claim, so it does not count toward the Established threshold.
The claim rests on a single anchor whose finding affirms it; a second independent affirming anchor is needed to reach Established.

Key results

A Garmin fenix 6 met its pre-set validation criteria for VO2 max against laboratory testing, with a mean absolute percentage error of 7.05 percent and concordance of 0.73. (Carrier et al., Sensors, 2025)
Apple Watch Series 10 underestimated VO2 max by 6.25 mL/kg/min on average in 40 adults (limits of agreement -18.23 to 5.73), a 13.2 percent error, and placed 5 of 40 people in their correct fitness percentile. (Lambe et al., Mayo Clinic Proceedings Digital Health, 2026)
Google Pixel Watch 3 had a low average bias of -0.53 mL/kg/min in 34 adults but limits of agreement from -12.56 to 11.50, which the authors judged insufficient for individual clinical use. (Lambe et al., PloS One, 2026)

What this finding covers

Applies to: VO2 max estimates from consumer watches compared with maximal laboratory testing with breath analysis.

Does not cover: Whether VO2 max predicts lifespan, which is a separate and well-established question; models not tested.

Limitations

Studies are small, typically 30 to 40 participants.
Several of the studies come from one research group.

Evidence base

9 studies scored · 5 anchor · 4 supporting · Evidence last evaluated Oct 17, 2026

Anchor studies

The studies the rating rests on.

Accuracy of VO2 max Estimates From Apple Watch Series 10Lambe et al., Mayo Clinic Proceedings Digital Health, 2026. doi.org/10.1016/j.mcpdig.2026.100357
The accuracy of VO2 max, heart rate and energy expenditure measurements from Google Pixel Watch 3.Lambe et al., PloS One, 2026. doi.org/10.1371/journal.pone.0356808 [conflict statement: funded by Google]
Investigating the accuracy of Apple Watch VO2 max measurements: A validation study.Lambe et al., PloS One, 2025. doi.org/10.1371/journal.pone.0323741
Validation of Aerobic Capacity (VO2max) and Pulse Oximetry in Wearable Technology.Carrier et al., Sensors, 2025. doi.org/10.3390/s25010275
Validity of Wrist-Worn Activity Trackers for Estimating VO 2max and Energy Expenditure.Passler et al., International Journal of Environmental Research and Public Health, 2020. doi.org/10.3390/ijerph16173037

Supporting studies

Studies consistent with the claim that do not carry the rating on their own.

Validity of the garmin Forerunner 265 to predict VO2max and race performance timesHoward et al., Journal of Medical Engineering & Technology, 2026. doi.org/10.1080/03091902.2026.2741912
Estimating oxygen uptake in simulated team sports using machine learning models and wearable sensor data: A pilot study.Sheridan et al., PloS One, 2025. doi.org/10.1371/journal.pone.0319760
Heart Rate Variability Based Estimation of Maximal Oxygen Uptake in Athletes Using Supervised Regression Models.Balakarthikeyan et al., Sensors, 2023. doi.org/10.3390/s23063251
Cardiorespiratory fitness estimation using wearable sensors: Laboratory and free-living analysis of context-specific submaximal heart rates.Altini et al., Journal of Applied Physiology (Bethesda, Md, 2017. doi.org/10.1152/japplphysiol.00519.2015

Version history

Version	Date	Rating	Change
1.0	October 24, 2026	Emerging	First published.

Rating history on the research desk: Emerging (July 9, 2026).

Cite this finding

KnowYourPrime Evidence Registry, Finding KYP-ER-0011, version 1.0, reviewed 2026-10-24. https://knowyourprime.com/evidence-wearable-vo2-max-accuracy

Machine-readable: JSON · Markdown · All findings

Research desk: the VO2 max research desk entry for this question, with every scored study and its role
Related finding: Wearable Heart Rate Accuracy (KYP-ER-0009)
On this site: How Wearables Estimate VO2 Max (And What Gets Lost)
On this site: Your Watch's VO2 Max Is a Formula. Does It Predict Lifespan?
On this site: VO2 Max Dropped? Its Own Study Called That Reliability Poor

This is KnowYourPrime's own assessment of the published evidence, rated under the KnowYourPrime evidence methodology. The rating is set by a fixed rule from the roles of the studies above and moves only when the evidence or the rule changes. Every change to the rating or the text is published as a new dated version. To report an error, write to corrections@knowyourprime.com.