VO2 Max: How to integrate this critical biomarker into clinical practice
Our CEO, Brooks Leitner, recently sat down with Sunita Mohanty, founder and CEO of Ultralight Health, to give a masterclass on VO₂ Max for clinicians focused on preventive, proactive, and longevity medicine.
1. What Is VO₂ Max and What Does It Measure?
VO₂ Max is the maximum amount of oxygen you can consume at a peak workload. You challenge the system to its maximal capacity, and it's a number.
The oxygen cascade
To achieve a good result, all of the body's systems need to be well-functioning. Oxygen literally comes from the environment through:
The lungs, where oxygen comes in and binds hemoglobin and red blood cells.
The heart and blood vessels, which pump it to the working skeletal muscle.
The mitochondria, where it diffuses into the electron transport chain. The final complex serves as the final electron acceptor of oxygen.
The brain plays a role too: the focus required, the cognitive effort.
The takeaway: If you really care about the function of all those systems and the way they all work together, you can get that from a single metric. That's why VO₂ Max is really a good one.
What about METs?
One MET (metabolic equivalent) is your resting energy expenditure—how much energy your body needs just to be alive, for the heart to beat.
METs are multiples of your resting energy expenditure. At maximum exercise, it can be anywhere from 5 to 20 METs in elite athletes.
METs assume 3.5 mLs per kg per minute, but it's not always 3.5. METs are actually a proxy for oxygen consumption.
Everything is anchored to VO₂ Max , including METs. VO₂ Max, or as close as possible to VO₂ Max, should be the metric used for population-level health.
2. Why Is It Important for Clinical Practice?
VO₂ Max is a great measure of functional capacity that has implications for aging. Here's why it matters:
It sets the ceiling for daily life. Carrying the groceries is maybe 20% of peak capacity for someone with a very high VO₂ Max . For someone with very low cardiorespiratory fitness, it could be up to 80%. At the far end, low exercise capacity impairs activities of daily living.
It flags risk before labs do. People in their 20s can have normal clinical labs and a normal A1C. But those with a low VO₂ Max are likely to develop some sort of chronic disease within the next 5 years rather than 20. That's borne out with the epidemiological research.
It looks upstream. Many blood tests are designed to detect disease. If you actually want to prevent disease, you need to look upstream: at the functions of the body that decline before disease arises.
It measures what matters. Fitness and body composition are upstream of the vast majority of other biomarkers. You don't need every single biomarker; you need the ones that really have outsized returns on the interventions that follow.
3. How Can You Measure It?
There are several ways to measure or estimate VO₂ Max :
Method | What to know |
|---|---|
Gold-standard VO₂ Max test | A maximal exercise test. It's a really hard test, and it's hard to get people to come back for a repeat, even elite athletes. |
METs | If you can do a maximal exercise test, it correlates quite well. |
12-minute Cooper test | A maximal 12-minute test, pretty accurate. |
Wearables | Apple Watch, Garmin, Whoop, etc. Accuracy is capped by the best published models to date. |
Blood Test (VO Health’s Molecular Fitness Blood Test) | VO Health's Molecular Fitness Blood Test, a simple blood draw. |
The blood test at a glance
What it measures: VO₂ Max and the 10 biological pathways underlying fitness, including fat metabolism, inflammation, oxidative stress, and more.
How it works: It measures a thousand proteins, narrowed down to the 50 that can predict VO₂ Max . These come from all of the tissues in the body—heart, lung, blood vessels, blood, muscle, brain even—because all of those systems are actually captured in the blood.
How it's collected: An IV blood draw that ships at ambient temperature for up to 5 days, or a Tasso self-collection blood draw validated up to 3 days at ambient temperature.
How accurate is it? | Blood test | For comparison |
|---|---|---|
R² (how much of your true VO₂ Max it explains) | 0.89 (89%) | 0.71, the previous Nature Medicine best |
Mean absolute percentage error | Around 10%, across ages 18 to 82 and VO₂ Maxes from 13.3 to 77.6 | |
Retest difference (two days apart) | 0.9% | 4 to 8% for the gold-standard test |
Beyond the number: Two people with the same VO₂ Max might need a different precision intervention. For example, people with normal CRP can have inflammation scores associated with regular alcohol use, poor quality diets, and a recent injury—very subtle inflammation even before you see an elevation in high-sensitivity CRP.
4. How to Integrate It Into Clinical Practice
Medicine requires a simple up/down, yes/no in order to prompt a prescription or decision. If cholesterol is high, prescribe a statin. If A1C is high, metformin or maybe a GLP-1. We would like to see clinicians flagging VO₂ Max low, and the prescription is fitness.
A good biomarker should be able to flag risk or demonstrate response efficacy. Here's where VO₂ Max fits:
Use case | Why | How often to test |
|---|---|---|
Flagging accelerated decline | People lose about 10% of their VO₂ Max per decade after age 30. Declining 3 to 5% in a year, two years in a row, could put a patient at risk for cardiovascular disease and issues of functional capacity. | Annually for the general population; quarterly with high suspicion |
Monitoring training response | Track the response to an exercise training intervention. | Monthly on a 3-month exercise protocol |
Monitoring fitness during weight loss | As kilograms come down, VO₂ Max should go up. If it doesn't, you may be losing active skeletal muscle or lean tissue. | Quarterly over a focused period, maybe over a year |
Fit for surgery | People with higher cardiorespiratory fitness have shorter hospital stays postsurgery. | Around 12 weeks before a planned surgery, to prompt a six- or eight-week exercise intervention |
Cancer rehabilitation | Flag survivors at 16 mLs per kg per minute or lower, where you see high risk of falls and other injuries. | To prompt an exercise rehabilitation program |
Writing the exercise prescription: FITT
Frequency, Intensity, Time, and Type of exercise are the modulators you can toggle in order to deploy an exercise prescription.
Rule of thumb: The shorter the time someone can dedicate to exercise each week, the higher percentage of high-intensity exercise it should be.
One hour per week: around half should be higher-intensity exercise.
Three to four hours per week: a quarter or a third high intensity, and the rest low or moderate intensity.
It doesn't have to be running. Swimming, rowing, and biking all count.
Finally, in order to improve fitness, you really need a trusted person to help enable behavior change.
Watch the Full Webinar for More
This is just a piece of the conversation between Sunita Mohanty and Brooks Leitner on VO₂ Max, cardiorespiratory fitness as a metric of longevity, and how to bring it into your practice. Watch the full webinar for the science, the special populations, and how proteomics and AI fit into the future of preventive care.
