The units of VO₂ max are millilitres of oxygen per kilogram of body weight per minute, written as: ml/kg/min. This unit reflects how many millilitres of oxygen your body can use per minute, for every kilogram you weigh. It allows VO₂ max to be compared fairly across individuals of different sizes.

1. Understanding VO₂ max: The Fitness Number That Actually Matters

VO₂ max measures how much oxygen your body can use during peak exercise. It reflects the efficiency of your heart, lungs, blood vessels, and muscles. Unlike weight or cholesterol, it directly reveals how well your body can produce and sustain energy. This number, measured in millilitres per kilogram per minute, is one of the strongest predictors of long-term health and survival.

2. My Starting Point: A Wake-Up Call at 35 years old

In 2022, aged 35, my VO₂ max was 38. While not terrible for my age, my Garmin told me it was in the bottom 25% for my age and gender. This may be considered average on some metrics, but average is not good enough. Studies show that people with low cardiorespiratory fitness have up to a fivefold increase in mortality risk compared to those with high fitness levels. I knew I had to act.

3. Why I Chose VO₂ max as My North Star

Of all the health metrics, VO₂ max stands out because it cannot be hacked or manipulated. It demands consistency, intensity, and effort. It is also remarkably responsive to training. Increasing VO₂ max improves everything from cardiovascular and brain health to immune function and emotional resilience.

4. What the Science Says About Longevity

Each 1-point increase in VO₂ max is linked to a 13 percent reduction in all-cause mortality. Improving mine from 38 to 51 (top 15%) over two years gave me a roughly 170 percent higher cardiorespiratory capacity. This is associated with significantly reduced risk of chronic disease and early death.

5. What I Did: A Mix of HIIT and Steady State Cardio

The core of my training was zone 2 longer steady-state sessions to build an aerobic base. Zone 2 is typically 60 to 70 percent of your maximum heart rate, for me this was about 128-142 bmp and at first that meant walking – jogging/running I would quickly exceed this range. This was paired with high-intensity interval sessions; short bursts of near-max effort followed by rest.  Research confirms this combination is the most effective for raising VO₂ max across all fitness levels.

6. My Progress: Measurable, Meaningful Change

VO₂ max tests over time showed steady improvements. I retested every few months using both lab equipment and validated wearables. Seeing my number climb was incredibly motivating. I was not just getting fitter. I was extending my healthspan, the years I can live independently and disease-free.

7. The Ripple Effect: Better Energy, Sleep, and Focus

Beyond the numbers, I noticed real-life benefits. I had more energy throughout the day. My sleep improved. My mood and cognitive function felt sharper. These are the effects of better oxygen delivery and mitochondrial function; benefits that are measurable at the cellular level.

8. Why Strength Training Was Not Enough

I continued lifting weights for strength and muscle mass, but it was my aerobic and interval training that moved the needle on VO₂ max. Strength is essential for aging well, but without high cardiorespiratory fitness, you are not truly protected.

9. The Big Picture: A Foundation for Longevity

Improving VO₂ max has become a foundation of my long-term health strategy. It is a vital sign that predicts quality of life, not just lifespan. If you care about staying independent, avoiding disease, and being fully alive well into older age, then this is the number to watch.

10. The Takeaway: Make It Your Priority

No supplements or tech can replace the work. VO₂ max responds to effort and consistency. I built mine through structured cardio, patience, and commitment. Anyone can do the same, it just takes intention.

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References

1. Kodama S et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality. JAMA. 2009.

2. Strasser B, Burtscher M. VO₂ max and survival in aging. Front Biosci. 2018.

3. American Heart Association. VO₂ max as a vital sign in clinical practice. 2016.

4. Wisløff U et al. Superior cardiovascular effect of aerobic interval training. Circulation. 2007.

5. The Times. “The number that predicts how long you will live” featuring Peter Attia. 2023.