VO₂ Max: The Health Number You Probably Aren’t Paying Attention To
We track our weight, blood pressure, cholesterol and steps. But there is another number that can tell us something important about how well our heart, lungs and muscles are working together.
Most people have heard of blood pressure, resting heart rate, cholesterol and blood sugar. If you wear a smartwatch, you may also be tracking your steps, sleep and heart rate.
But there is another health number you may have noticed without really knowing what it means: VO₂ max.
The name sounds like something reserved for marathon runners, cyclists and elite athletes. But VO₂ max is really a measure of cardiorespiratory fitness, and that matters whether your goal is to run a marathon or simply remain strong, active and independent as you get older.
VO₂ max is not just about athletic performance.
Think of it as one indicator of your body's capacity to do work.
1. What Exactly Is VO₂ Max?
VO₂ max refers to the maximum amount of oxygen your body can take in and use during intense exercise.
When you exercise, your lungs bring oxygen into your body. Your heart pumps oxygen-rich blood to your working muscles. Those muscles then use oxygen to help produce energy.
VO₂ max gives us an indication of how effectively that entire system works together.
It is usually expressed as milliliters of oxygen used per kilogram of body weight per minute, or mL/kg/min.
A higher VO₂ max generally means your body has a greater ability to deliver and use oxygen during exercise.
2. Why Should You Care If You're Not an Athlete?
This is where VO₂ max gets really interesting.
Cardiorespiratory fitness is strongly associated with long-term health. The American Heart Association has gone so far as to suggest that cardiorespiratory fitness deserves consideration as a clinical vital sign.
Research has consistently found that lower cardiorespiratory fitness is associated with greater cardiovascular and all-cause mortality risk.
That does not mean VO₂ max predicts exactly how long someone will live. Health and longevity are much more complicated than one number.
But it does mean that your aerobic fitness tells us something valuable about your overall physiological capacity.
The encouraging part?
You do not need elite-level fitness to benefit. Moving from very low fitness to even moderately better fitness can matter.
3. VO₂ Max Changes as We Age
VO₂ max tends to decline with age. That is normal.
Large cardiorespiratory fitness databases have found substantial differences based on age, sex and the type of exercise test performed.
In one large U.S. reference database known as the FRIEND Registry, researchers analyzed thousands of cardiopulmonary exercise tests and found that VO₂ max generally declined across the decades of adulthood.
Earlier FRIEND data found roughly a 10 percent decline per decade across several decades of adulthood. Updated research continues to show that age, sex and testing method matter when interpreting an individual's result.
Instead of obsessing over one universal "perfect" number, it can be much more useful to look at your fitness relative to appropriate reference values and, perhaps even more importantly, to follow your own trend over time.
4. How Is VO₂ Max Actually Measured?
The most accurate measurement typically comes from a cardiopulmonary exercise test, often called a CPET or CPX test.
During the test, you exercise on a treadmill or stationary bicycle while wearing a mask that measures the oxygen you inhale and the gases you exhale. The workload gradually increases while your cardiovascular and respiratory responses are measured.
This is very different from the estimate you may see on your smartwatch.
What about Apple Watch, Garmin and other wearables?
Many modern wearables estimate VO₂ max using information such as heart rate, pace, speed, age, sex and exercise patterns.
These estimates can be useful for watching trends, but they are not the same as directly measuring oxygen consumption in a laboratory.
If your watch suddenly tells you your VO₂ max dropped a point, there is usually no reason to panic. Heat, hydration, fatigue, illness, terrain, medications and even the type of workout can influence exercise data.
One number is a snapshot. Patterns over time are usually more useful.
5. Can You Improve Your VO₂ Max?
Yes. And this is probably the most important part of the conversation.
Genetics and age influence VO₂ max, but cardiorespiratory fitness is also trainable.
You do not necessarily need brutal workouts, endless running or an expensive exercise program.
The goal is to regularly challenge your cardiovascular system enough that it has a reason to adapt.
Start With Consistent Aerobic Exercise
Brisk walking, cycling, swimming, hiking, jogging and other activities that elevate your heart rate can all contribute to cardiovascular fitness.
Current U.S. physical activity guidelines recommend that most adults aim for at least 150 minutes of moderate-intensity aerobic activity each week, or 75 minutes of vigorous activity, or an equivalent combination.
Add Some Intensity When Appropriate
Once you have established a fitness base, periods of higher-intensity exercise can provide an additional cardiovascular challenge.
Research shows that interval training can improve VO₂ max, including in middle-aged and older adults.
That does not mean everyone needs to sprint.
An interval could be as simple as walking briskly up a hill, increasing your pace for a short period, then slowing down to recover before repeating.
Keep Strength Training Too
Cardiovascular fitness is important, but it is only one piece of healthy aging.
Adults should also include muscle-strengthening exercise at least two days per week. Maintaining muscle, strength, balance and cardiovascular capacity together helps support the ability to keep doing the things we enjoy.
6. A Simple Way to Start
If you have been fairly inactive, you do not need to start by worrying about zones, percentages or complicated training formulas.
Try building from the basics:
Step 1: Walk regularly and build consistency.
Step 2: Gradually increase your pace so some walks feel moderately challenging.
Step 3: Add hills, stairs or brief faster intervals when appropriate.
Step 4: Continue strength training at least twice per week.
Step 5: Track how you feel and what you can do, not just what your watch says.
If you have cardiovascular disease, significant health concerns, symptoms with exercise or have been inactive for a long period, talk with your healthcare professional before beginning vigorous exercise or interval training.
7. The Number Is Useful, But Your Life Is the Real Test
I love health data when it helps us make better decisions.
But I never want a number on a watch to become the goal itself.
The real question is:
Can your body keep up with the life you want to live?
Can you walk up the stairs without becoming completely winded?
Can you carry your groceries?
Can you walk the golf course, hike on vacation, travel through an airport, play with your grandchildren or spend an active day doing something you love?
Those things require capacity.
And that is why cardiovascular fitness becomes increasingly important as we get older.
The Bottom Line
VO₂ max may sound like a number for serious athletes, but the bigger story is about your body's ability to deliver oxygen and produce energy when you need it.
You do not need to become a runner. You do not need to chase someone else's number. And you certainly do not need to turn every workout into a competition.
Build your cardiovascular fitness because you are building capacity for life.
We spend a lot of time trying to add years to our lives. I am just as interested in making sure we have the strength, energy and capacity to enjoy those years.
Wendy Francis, NBC-HWC
Ready to Work on Your Health From the Basics Up?
Health does not have to be complicated. Together, we can look at exercise, nutrition, sleep, stress and the everyday habits that support how you want to live.
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Wendy Francis, NBC-HWC
Board-Certified Health Coach
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Sources & Further Reading
- American Heart Association. Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign. Read more
- Kaminsky LA, et al. Updated Reference Standards for Cardiorespiratory Fitness Measured with Cardiopulmonary Exercise Testing: Data from the FRIEND Registry. Mayo Clinic Proceedings. View study
- Centers for Disease Control and Prevention. Physical Activity Guidelines for Adults. Read guidelines
- Støren Ø, et al. and related research on cardiorespiratory fitness and interval training. National Library of Medicine. View research