You wouldn’t ignore your blood pressure. So why are you ignoring this?

If you could measure your body’s capacity for survival, would you?

You already track some of it:

Blood pressure.
Resting heart rate.
Blood glucose.
Temperature.

These numbers earn the title vital signs because they’re:

Quick to measure
Non-invasive
Predictive of health outcomes
Actionable

But there’s another measure that meets—and often exceeds—those criteria.

It’s more predictive than most vitals you already know. It’s trainable.

And it’s repeatable. VO₂ Max.

What Makes a Vital Sign

In medicine, a vital sign must be:

Predictive — Reliably forecasts health outcomes or risk.
Repeatable — Consistent when measured under the same conditions.
Actionable — Can guide intervention and track progress.
Non-invasive — Safe and quick to measure.

By this definition, VO₂ Max qualifies in every category—often with fewer limitations than the metrics we routinely collect.

VO₂ Max vs. Traditional Vitals

  
    
        Criteria
        VO₂ Max
        Blood Pressure
        Glucose
        Heart Rate
      

    
        Predictive Power
        10
        7
        7
        6
      

        Repeatability
        8
        6
        5
        7
      

        Actionable / Trainable
        10
        7
        8
        6
      

        Non-Invasive
        8
        9
        9
        9
      

  

Why this matters: VO₂ Max shows ~3–5% variability in controlled labs, vs. 10–20% for BP depending on cuff, positioning, and pre-test conditions [4,5]. It’s also one of the few vitals you can improve 10–20% in a matter of months.

The Predictive Power

Large-scale studies confirm it:

Mandsager et al., 2018 — In 122,007 adults, cardiorespiratory fitness was the strongest predictor of all-cause mortality. Top quartile had ~70% lower risk of death; elite (top 2.5%) ~80% lower risk than the lowest quartile [1].
Kokkinos et al., 2022 — In over 750,000 U.S. veterans, each 1-MET increase (~3.5 ml/kg/min) in VO₂ Max cut mortality risk by 13–15%, independent of age, BMI, or comorbidities [2].
Kodama et al., 2009 — Meta-analysis of 33 cohorts: each 1-MET gain lowered all-cause mortality by 13% and cardiovascular events by 15% [3].
Ross et al., 2016 — Systematic review: low fitness carries higher mortality risk than hypertension, smoking, or diabetes in multiple cohorts [6].

Why It’s Been Overlooked

Historically, VO₂ Max testing required research-grade equipment and trained staff.

Medicine defaulted to resting measures like BP and HR—easier to collect in a clinic but less representative of what happens when your system is under load.

The problem: most health crises don’t happen at rest.

The Flaws in Familiar Vitals

Even trusted vitals have limitations:

Blood pressure — Can vary by 20+ mmHg from cuff size, positioning, caffeine, stress, or operator technique [4,5].
Glucose — Swings with the last meal, hydration status, or acute illness.
Heart rate — Changes with hydration, sleep, temperature, and stress.

Yet we make major decisions—sometimes starting lifelong medication—based on these numbers, even when precision is questionable.

Why VO₂ Max Should Be Your Base Layer

Think of it as the foundation under every other reading.

If your VO₂ Max is high—say, in the top 25% for your age and sex—you’ve built a reserve that strongly offsets other risks.

Imagine:

You get a borderline-high BP reading at your check-up. The cuff was a poor fit, you were stressed from traffic, and there was no rest period. Based on that one number, you’re prescribed a drug with side effects.

Now imagine the alternative:

You also know your VO₂ Max, measured in a lab. It’s in the top quartile—a range tied to drastically lower mortality and cardiovascular risk. You focus on training, Zone 2 aerobic work, and outdoor light exposure (which also lowers BP via nitric oxide release [7]).

A few months later, both your VO₂ Max and BP look better—without unnecessary medication.

Wearables: Useful, But Validate

Consumer devices estimate VO₂ Max from heart rate, pace, and sometimes HRV. They’re good for spotting trends, but have 10–20% average error vs. direct gas-exchange testing [8,9].

Accuracy depends on:

Steady-state conditions
Correct user data (age, weight, resting HR)
Activity type (running works best; cycling, swimming less so)
Brand-specific algorithms

Best practice: Use wearables for day-to-day guidance, but validate annually or biannually with a direct VO₂ Max test—especially if your goal is to reach or stay in the top quartile.

DexaFit’s Approach

We treat VO₂ Max like the foundational vital sign it is:

Direct measurement with metabolic carts—no algorithmic guesswork.
4-zone training model from your personal ventilatory thresholds.
6–9 month re-tests to track true adaptation.
Integration with body composition and other key metrics for a complete picture.

Know Before You Act

Before starting a prescription, injection, or surgery—know your VO₂ Max.

It’s your aerobic reserve, your functional capacity, and one of the strongest independent predictors of how long and how well you’ll live.

Test it. Train it. Retest it.

Treat it like your health depends on it—because the data says it does.

References

Mandsager K, et al. JAMA Netw Open. 2018;1(6):e183605.
Kokkinos P, et al. J Am Coll Cardiol. 2022;80(6):598–609.
Kodama S, et al. JAMA. 2009;301(19):2024–2035.
Passarella S, et al. J Hum Hypertens. 2014;28(5):301–306.
Pickering TG, et al. Hypertension. 2005;45(1):142–161.
Ross R, et al. Prog Cardiovasc Dis. 2016;59(5):448–455.
Liu D, et al. J Invest Dermatol. 2014;134(7):1839–1846.
Dürr S, et al. Eur J Appl Physiol. 2019;119(6):1335–1344.
Hansen D, et al. JMIR Mhealth Uhealth. 2024;12:e49066.

Why VO₂ Max Is a Vital Sign (and Should Be Treated Like One)