What Your VO2 Max Reveals About Your Health
By: Brian Hoeflinger, MD
August 16, 2026 | #90
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Disclaimer: Opinions are my own. Not medical advice.
Medical Trivia of the Week
Four of your five senses pass through a relay station deep in the brain, the thalamus, on their way to the cortex. Which one goes around it? (the correct answer is at the end of this email)
- A) Sight
- B) Hearing
- C) Touch
- D) Smell
In Today's Newsletter
- Most people could tell me their blood pressure. Not nearly as many could tell me their VO2 max.
- It is one of the most useful numbers in relation to a person's overall health.
- Today, I'll explain to you what VO2 max is, what the research actually says, how to find yours, and how to improve it.
What is VO2 Max?
VO2 max is the most oxygen your body can use during hard effort. Think of it as the size of your engine.
It matters because it isn't one measurement. It's your whole system graded at once. Your lungs move air. Your heart pumps blood. Your vessels deliver it. Your muscles burn it.
Weaken any link and the number falls. That's why it's hard to fake.
Why is VO2 Max Important?
In 2018, Cleveland Clinic researchers published one of the largest studies of its kind.
The setup:
- 122,007 adults who took a treadmill stress test between 1991 and 2014
- Followed for a median of 8.4 years
- 13,637 deaths across 1.1 million person-years
- Sorted into five fitness groups, from low to elite
- Adjusted for age, sex, body mass index, heart disease, diabetes, blood pressure, cholesterol, kidney disease, smoking, and medications
The least fit group had roughly five times the death risk of the most fit group.
Striking. But here's what I believe is the even more interesting finding.
Being one step below average carried about a 41 percent higher risk of death than being one step above average.
In that same study, with the same adjustments:
- Smoking: 41 percent
- Diabetes: 40 percent
- Known coronary artery disease: 29 percent
Read that again. The gap between slightly below average fitness and slightly above average fitness carried about the same risk as smoking. Two more things worth knowing.
- There was no ceiling. The researchers went looking for a point where more fitness stopped helping. They didn't find one.
- The benefit held in patients over 70. If you're older, this matters more, not less.
What This Study Can't Prove
This was observational, not a trial. It shows association, not cause. Correlation does not equal causation. Nobody was assigned to be fit.
The researchers said plainly they can't separate how much comes from fitness itself and how much comes from healthy people simply being able to exercise. It also studied people referred for a stress test, not the general public.
So it isn't proof that raising your fitness adds years. It's strong evidence that fitness tracks with survival more tightly than almost anything else we measure. That's enough for me to take seriously and act on.
How to Find Your VO2 Max This Week
Two ways, and neither costs anything.
1. A free online calculator. Norwegian researchers built one from thousands of directly measured tests. Enter your age, waist, resting heart rate, and activity level. It takes about a minute and needs no equipment.
2. Your watch. If you wear a smartwatch or fitness ring, it may already be tracking this without you knowing. I wear a Garmin, and mine currently reads 43.
I want to be clear about what that number is and isn't. My watch is not measuring the oxygen I use. It is estimating, based on my heart rate and pace. The real number could be several points in either direction.
That is fine. I am not looking for precision. I am looking for direction. If it reads 43 now and 46 next spring, the training is working. If it drifts down, something needs to change.
Check under cardio fitness or VO2 max in your app. You may have months of data sitting there already.
What about getting it measured properly? There is a real test. You wear a mask on a treadmill or a bike while a machine measures the oxygen you actually consume. That is the gold standard.
However, the majority of people do not need the lab. It costs money, it requires finding a facility, and for what you are trying to do here, it does not tell you anything an estimate won't.
Furthermore, the Cleveland Clinic study I just described didn't use that test either. Those researchers estimated fitness from treadmill speed and incline.
Whichever you use, the trend matters more than the number. Take a reading this week. Implement a solid exercise routine. Take a reading regularly and track the trend. Adapt your plan as needed.
How to Improve Your VO2 Max
The number responds to training at any age. Researchers pooled 41 controlled trials covering 2,102 adults aged 60 and older. Previously sedentary people improved their VO2 max by an average of 16.3 percent compared with those who didn't train.
You don't have to suffer for it. In that same analysis, the biggest gains were linked to moderate intensity, not the hardest training.
The rule: talk, don't sing.
Walk briskly enough that you can hold a conversation but couldn't comfortably sing. That's the zone. Here's what the researchers actually used:
- 30 to 35 minutes per session
- Three times a week
- For 16 to 20 weeks
Longer than 20 weeks produced bigger gains. So give this four to five months before you judge it. Most people quit at six weeks and conclude it didn't work.
Before you push harder: if you have known heart disease, chest pain, unusual shortness of breath, or you've been sedentary a long time, talk to your primary care physician first. That conversation is exactly what a stress test is for.
One more thing worth knowing. In the Cleveland Clinic data, the single biggest drop in risk came at the bottom of the range, moving from the least fit group up to the next one. That one step was worth about as much as the next two combined.
So if your number comes back low, that is not bad news. It means you have the most to gain from the least work.
The Bottom Line
VO2 max isn't really about living longer. It's about whether you can carry groceries up the stairs at 80. Whether you can keep up with your grandchildren. Whether an illness knocks you down for a week or for good. It's the reserve you draw on when life asks something of you.
I retired from full-time neurosurgery a few weeks ago because I wanted my remaining years to be good ones, not just more of them. This is the number that decides that. In September, my son Kevin and I are racing a half Ironman. I'm almost 62. I'm not that fast and I'm not trying to be. I'd rather build the engine now than wish I had later.
You don't need to race anything. Know your number. And then make it go up.
Impactful Quote of the Week
"It is not the mountain we conquer, but ourselves."
- Sir Edmund Hillary
Please let me know what you thought of this newsletter by replying to this email. I strive to read and reply to as many as I can.
All my best,
Brian Hoeflinger
P.S. - If you enjoyed this newsletter, you may enjoy my book that details my life as a neurosurgeon and the loss of my oldest son, Brian (synopsis below).
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Medical Trivia Answer:
The correct answer is D) Smell
Sight, hearing, touch, and taste all route through the thalamus before reaching the cortex. Smell skips it, traveling from your nose into the limbic system and reaching the amygdala, the brain's emotional center, in as few as two synapses. That shortcut is why a scent can bring back a memory with more emotion than a photograph of the same thing.
Want to read past issues? Read the archive here.
*Disclaimer: This newsletter and blog is for general informational purposes only and does not constitute the practice of medicine, nursing, or other professional health care services, including the giving of medical advice, and no doctor/patient relationship is formed. The use of information on this newsletter and blog or materials linked from this newsletter and blog is at the user’s own risk. The content of this newsletter and blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard or delay seeking medical advice for any medical condition they may have and should consult their healthcare professionals for any such conditions.
