{
  "registry": "KnowYourPrime Evidence Registry",
  "license": {
    "name": "CC BY 4.0",
    "url": "https://creativecommons.org/licenses/by/4.0/",
    "attribution": "Credit KnowYourPrime and link to the finding URL."
  },
  "fields": {
    "devices": "Devices this finding names, including models it says it does not cover. What was actually tested is in scope.applies_to; exclusions are in scope.does_not_cover.",
    "evidence": "Studies by role: anchor (the rating rests on it), conflicting, null_result, supporting.",
    "industry_ties": "Device-maker ties listed in Europe PMC metadata: author_affiliations names makers an author lists as an affiliation, funders names makers listed as funding. stated_ties holds ties a paper states only in its own conflict, funding or acknowledgement text, each read from that statement and worded to say only what it says. Sources are Europe PMC metadata, funding printed in the abstract, and those reviewed statements. An empty list means no tie was found there, not that the study is independent: many papers have no open full text to read. Metadata, not a judgment of the study. checked false means no Europe PMC metadata was available."
  },
  "id": "KYP-ER-0011",
  "version": "1.0",
  "reviewed": "2026-10-24",
  "url": "https://knowyourprime.com/evidence-wearable-vo2-max-accuracy",
  "title": "Wearable VO2 Max Estimate Accuracy",
  "question": "Are smartwatch VO2 max estimates accurate against a laboratory treadmill or cycle test?",
  "measurement": "VO2 max (cardio fitness)",
  "devices": [
    "Apple Watch",
    "Garmin",
    "Google Pixel Watch"
  ],
  "rating": {
    "label": "Emerging",
    "code": "emerging",
    "definition": "Evidence currently favors the claim, but more confirmation is needed.",
    "rule_version": "1.4",
    "rule_reasons": [
      "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."
    ]
  },
  "conclusion": "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.",
  "reasoning": [
    "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."
  ],
  "key_results": [
    {
      "text": "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.",
      "source": "doi:10.3390/s25010275",
      "source_url": "https://doi.org/10.3390/s25010275",
      "source_citation": "Carrier et al., Sensors, 2025"
    },
    {
      "text": "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.",
      "source": "doi:10.1016/j.mcpdig.2026.100357",
      "source_url": "https://doi.org/10.1016/j.mcpdig.2026.100357",
      "source_citation": "Lambe et al., Mayo Clinic Proceedings Digital Health, 2026"
    },
    {
      "text": "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.",
      "source": "doi:10.1371/journal.pone.0356808",
      "source_url": "https://doi.org/10.1371/journal.pone.0356808",
      "source_citation": "Lambe et al., PloS One, 2026"
    }
  ],
  "scope": {
    "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": {
    "anchor": [
      {
        "key": "doi:10.1016/j.mcpdig.2026.100357",
        "title": "Accuracy of VO2 max Estimates From Apple Watch Series 10",
        "first_author": "Rory Lambe",
        "journal": "Mayo Clinic Proceedings Digital Health",
        "year": 2026,
        "url": "https://doi.org/10.1016/j.mcpdig.2026.100357",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1371/journal.pone.0356808",
        "title": "The accuracy of VO2 max, heart rate and energy expenditure measurements from Google Pixel Watch 3.",
        "first_author": "Lambe",
        "journal": "PloS one",
        "year": 2026,
        "url": "https://doi.org/10.1371/journal.pone.0356808",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": [
            "conflict statement: funded by Google"
          ]
        }
      },
      {
        "key": "doi:10.1371/journal.pone.0323741",
        "title": "Investigating the accuracy of Apple Watch VO2 max measurements: A validation study.",
        "first_author": "Lambe",
        "journal": "PloS one",
        "year": 2025,
        "url": "https://doi.org/10.1371/journal.pone.0323741",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.3390/s25010275",
        "title": "Validation of Aerobic Capacity (VO2max) and Pulse Oximetry in Wearable Technology.",
        "first_author": "Carrier",
        "journal": "Sensors (Basel, Switzerland)",
        "year": 2025,
        "url": "https://doi.org/10.3390/s25010275",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.3390/ijerph16173037",
        "title": "Validity of Wrist-Worn Activity Trackers for Estimating VO 2max and Energy Expenditure.",
        "first_author": "Passler",
        "journal": "International journal of environmental research and public health",
        "year": 2020,
        "url": "https://doi.org/10.3390/ijerph16173037",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      }
    ],
    "supporting": [
      {
        "key": "doi:10.1080/03091902.2026.2741912",
        "title": "Validity of the garmin Forerunner 265 to predict VO2max and race performance times",
        "first_author": "Jonathan Howard",
        "journal": "Journal of Medical Engineering & Technology",
        "year": 2026,
        "url": "https://doi.org/10.1080/03091902.2026.2741912",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1371/journal.pone.0319760",
        "title": "Estimating oxygen uptake in simulated team sports using machine learning models and wearable sensor data: A pilot study.",
        "first_author": "Sheridan",
        "journal": "PloS one",
        "year": 2025,
        "url": "https://doi.org/10.1371/journal.pone.0319760",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.3390/s23063251",
        "title": "Heart Rate Variability Based Estimation of Maximal Oxygen Uptake in Athletes Using Supervised Regression Models.",
        "first_author": "Balakarthikeyan",
        "journal": "Sensors (Basel, Switzerland)",
        "year": 2023,
        "url": "https://doi.org/10.3390/s23063251",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1152/japplphysiol.00519.2015",
        "title": "Cardiorespiratory fitness estimation using wearable sensors: Laboratory and free-living analysis of context-specific submaximal heart rates.",
        "first_author": "Altini",
        "journal": "Journal of applied physiology (Bethesda, Md. : 1985)",
        "year": 2017,
        "url": "https://doi.org/10.1152/japplphysiol.00519.2015",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      }
    ]
  },
  "evidence_last_evaluated": "Oct 17, 2026",
  "rating_history": [
    {
      "date": "2026-07-09",
      "rating": "Emerging",
      "from": null,
      "rule_version": "1.4"
    }
  ],
  "versions": [
    {
      "version": "1.0",
      "date": "2026-10-24",
      "rating": "Emerging",
      "change": "First published."
    }
  ],
  "research_desk": "https://knowyourprime.com/research-desk-vo2max#wearable_validity",
  "related_findings": [
    "https://knowyourprime.com/evidence-wearable-heart-rate-accuracy"
  ],
  "related_articles": [
    "https://knowyourprime.com/how-wearables-estimate-vo2-max",
    "https://knowyourprime.com/estimated-vo2-max-accuracy-longevity",
    "https://knowyourprime.com/vo2-max-dropped"
  ],
  "methodology": "https://knowyourprime.com/methodology",
  "citation": "KnowYourPrime Evidence Registry, Finding KYP-ER-0011, version 1.0, reviewed 2026-10-24. https://knowyourprime.com/evidence-wearable-vo2-max-accuracy"
}