VO2 max: what it is, how to measure it, and how to improve it after 35
A practical guide to understanding VO2 max, measuring it reliably, and improving it after 35 with validated protocols and watches that actually get it right.
You hit 35, you keep running or going to the gym, and suddenly everyone is talking about VO2 max as if it were the definitive thermometer of your cardiovascular health. Your watch throws a number at you, you compare it with your brother-in-law’s, and you don’t know whether to worry or celebrate.
This article is for you if you are between 35 and 55 years old, train regularly (or want to start again), and want to understand what that figure really measures, how to obtain it as accurately as possible, and what to do to raise it. No miracles, just protocols that work.
What VO2 max is and why it matters after 35
VO2 max is the maximum amount of oxygen your body can consume and use during intense exercise, measured in milliliters of oxygen per kilogram of body weight per minute (ml/kg/min). The higher it is, the better your heart, lungs, and mitochondria work as a team.
It matters because it is one of the most powerful predictors of mortality we know. A study by Mandsager and colleagues published in JAMA Network Open (2018), covering 122,007 patients, showed that low VO2 max is associated with a higher risk of mortality than smoking, diabetes, or hypertension. It is not a sports vanity metric: it is a health marker.
From age 30 onward, VO2 max drops by roughly 10% per decade if you do nothing. With specific training, you can cut that decline in half or even reverse it for several years.
Normal VO2 max values by age and sex
These are indicative ranges based on data from the Cooper Clinic and the American Heart Association:
| Age (men) | Low | Medium | Good | Excellent |
|---|---|---|---|---|
| 30–39 | <35 | 35–42 | 43–50 | >50 |
| 40–49 | <32 | 32–39 | 40–47 | >47 |
| 50–59 | <29 | 29–36 | 37–44 | >44 |
| Age (women) | Low | Medium | Good | Excellent |
|---|---|---|---|---|
| 30–39 | <28 | 28–33 | 34–40 | >40 |
| 40–49 | <26 | 26–31 | 32–38 | >38 |
| 50–59 | <22 | 22–28 | 29–36 | >36 |
If you are in the “medium” range and train 3 days a week, there is clear room for improvement. If you are in “low”, the margin is huge (and the good news is that beginners improve fastest).
How to measure VO2 max: from the laboratory to your wrist
Stress test with gas analyzer (gold standard)
This is the reference. Treadmill or bicycle, a mask that measures inhaled oxygen and exhaled CO₂, and an incremental protocol until exhaustion. Accuracy of ±3%. Cost: between €80 and €200 at private sports clinics. Recommended if you are over 40, have cardiovascular risk factors, or want serious data for training.
VO2 max test at home: options without equipment
- Cooper test: you run for 12 minutes at the maximum intensity you can sustain. Formula: VO2 max = (distance in meters − 504.9) / 44.73. Requires a track or a flat stretch.
- Rockport test: you walk 1.6 km as fast as possible and measure your final heart rate. Good for beginners or sedentary people over 50.
- 1.5-mile (2.4 km) test: you run that distance flat out and apply a formula based on time and age.
Estimated accuracy: ±10–15%. Enough to track progress, not to diagnose.
Watches that measure VO2 max: which are most accurate
Sports watches estimate VO2 max by combining heart rate, pace, age, and weight. The best algorithms have an error of 5–7% compared with the laboratory, according to a study by Passler et al. published in Sensors (2019).
Garmin
The current benchmark. Models such as the Garmin Forerunner 265 (around €450) or the Fenix 7 (from €600) use the Firstbeat algorithm, one of the most validated. It needs outdoor GPS runs and a good heart rate signal (a chest strap works better than optical sensing) to fine-tune the estimate.
Polar
The Polar Vantage V3 (€600) and the Pacer Pro (€300) offer the Running Performance Test and their own Fitness Test (with an H10 strap). The latter is done lying at rest and gives a decent estimate, especially useful if you don’t compete.
Apple Watch
The Apple Watch Series 9 and the Ultra 2 estimate VO2 max during outdoor walks and runs. Reasonable accuracy in mid-range values, tending to underestimate in trained athletes. Advantage: it records automatically without any setup.
Coros and Suunto
The Coros Pace 3 (€230) and the Suunto Race (€450) are solid alternatives with their own algorithms. In independent tests they tend to come in 1–2 points below Garmin, although the trend (going up or down over time) is reliable, which is what really matters.
Tip: don’t compare absolute numbers between brands. Compare the evolution within the same device.
How to improve VO2 max after 35: protocols with evidence
The Norwegian 4×4 protocol
Published by Helgerud et al. in Medicine & Science in Sports & Exercise (2007), it is the gold standard for raising VO2 max.
- Warm-up: 10 min easy.
- 4 sets of 4 minutes at 85–95% of your maximum heart rate (RPE 8–9).
- 3 minutes of easy jogging between sets.
- Cool-down: 5 min.
Frequency: 2 times per week for 8 weeks. Typical gains: +10 to +15% VO2 max in untrained people, +5 to +8% in trained ones.
Short 30/30 intervals
30 seconds at very high intensity (RPE 9), 30 seconds easy. 10–20 repetitions. Useful if the 4×4 feels like a mental wall. Less studied, but with comparable results in several trials.
Long runs at moderate intensity
Zone 2 (60–70% of max HR, you can talk in short sentences). 45–90 minutes. It doesn’t raise VO2 max as quickly as intervals, but it improves your aerobic base and efficiency. Combining both is what works best. A good warm-up beforehand reduces the risk of injury on interval days.
Sample week by level
- Beginner: 2 easy runs (30–40 min) + 1 session of 4×2 min hard efforts.
- Intermediate: 2 runs (one long, 60 min) + 1 session of 4×4 + 1 strength session.
- Advanced: 3–4 aerobic sessions (one long, one at threshold, one VO2 max) + 2 strength sessions.
Common mistakes and contraindications
- Doing intervals every day. The body adapts through rest, not during effort. At least 48 hours between hard sessions.
- Ignoring strength training. Stronger legs = better running economy = better functional VO2 max. Two sessions a week are enough.
- Obsessing over the watch number. It can vary by ±2 points due to hydration, sleep, or heat.
- Starting 4×4 without a base. If you haven’t run for years, start with 4–6 weeks of easy runs first.
- Skipping check-ups. If you are over 40, have hypertension, high cholesterol, or a family history of heart disease, get a stress test before adding hard intervals. Consult your doctor if you have any cardiovascular condition, are pregnant, or are returning from an injury.
Practical wrap-up: what to do this week
- Measure your starting point. Do the Cooper test on Saturday, or check your watch’s reading after 2–3 outdoor GPS runs.
- Schedule a 4×4 session for Tuesday or Wednesday. Note your heart rate in each set and your RPE.
- Add a long zone 2 run over the weekend, 45–60 minutes at a pace where you can talk without gasping.
FAQ
How long does it take to raise VO2 max?
With 2 weekly sessions of well-executed intervals, you will see measurable changes in 6–8 weeks. The size of the change depends on your starting point: the lower it is, the faster you improve.
Which watch measures VO2 max best?
Garmin with Firstbeat is currently the most validated in independent studies, followed by Polar. Accuracy improves if you use a chest strap and run outdoors with GPS. For everyday use, any of the three (Garmin, Polar, Apple) works to track the trend.
Can you improve VO2 max without running?
Yes. Cycling, rowing, swimming, and the elliptical all work if you reach the protocol’s intensities. Cycling is especially useful if you have joint discomfort.
Is VO2 max inherited?
Partly. Genetics explain 30–50% of baseline VO2 max and of the response to training, according to the HERITAGE Family Study. The rest is up to you.
Is it dangerous to do intervals at 95% of max heart rate at 45?
Not if you are healthy and have built an aerobic base beforehand. If you have cardiovascular risk factors, get a medical stress test before starting. It never replaces the judgment of your cardiologist.
