Of all the numbers your doctor or smartwatch can give you, VO2 max may be the one most closely tied to how long and how well you live. The good news: it responds to training at any age. Understanding VO2 max after 35 helps you slow the decline that comes with age and add years of capable, energetic living.
This guide explains what VO2 max is, why it matters, how to measure it and exactly how to train it in three to four hours a week alongside your strength work.
Key takeaways
- VO2 max is the most oxygen your body can take in and use during all-out exercise. It is the gold-standard measure of aerobic fitness.
- Higher cardiorespiratory fitness is strongly linked to lower risk of death from all causes, with no clear upper limit to the benefit in a large 2018 study.
- Aerobic capacity tends to fall with age, and the decline speeds up in later decades. Training can slow it substantially.
- Smartwatch estimates are useful for tracking trends but can be off by a wide margin for any one person.
- The most efficient approach is a base of easy “zone 2” cardio plus one weekly session of hard intervals such as the Norwegian 4×4.
What VO2 max actually measures
VO2 max is the maximum rate at which your body can take in oxygen and use it during intense exercise. It reflects how well your heart pumps blood, how well your lungs move air and how well your muscles extract and use that oxygen.
It is usually expressed in millilitres of oxygen per kilogram of bodyweight per minute (ml/kg/min). Because it is scaled to bodyweight, losing excess fat can raise your number even before your heart and lungs improve.
For context, Mayo Clinic gives rough reference points: sedentary adults often score in the 20s, fairly active people in the 40s and elite endurance athletes in the 70s or higher.
Why VO2 max matters after 35
It is one of the strongest predictors of longevity
In 2018, Mandsager and colleagues published a study in JAMA Network Open of more than 122,000 adults who did treadmill exercise tests at the Cleveland Clinic. Over a median follow-up of 8.4 years, people in the lowest fitness group had about five times the risk of death of those in the “elite” group. The authors judged the risk of poor fitness to be comparable to, or greater than, traditional risk factors such as smoking, diabetes and coronary artery disease.
Just as striking, they found no ceiling. The fittest group had lower mortality than the merely highly fit group.
That study was observational, so it shows a strong association rather than proof of cause. But it fits a large body of evidence. A 2009 meta-analysis in JAMA by Kodama and colleagues, pooling 33 studies, found that each 1-MET increase in fitness (about 3.5 ml/kg/min) was associated with roughly 13% lower all-cause mortality. In 2016, the American Heart Association published a scientific statement arguing that cardiorespiratory fitness should be treated as a clinical vital sign.
It is the engine behind everyday energy
A higher VO2 max means any given task, such as climbing stairs, carrying a child or playing a match, takes a smaller share of your maximum capacity. That translates into less fatigue, quicker recovery and more energy left at the end of a long day.
How VO2 max changes with age
Aerobic capacity does decline as you get older. In the Baltimore Longitudinal Study of Aging, which tracked 810 healthy adults over time, peak oxygen uptake fell by about 3–6% per decade in people in their 20s and 30s. The rate of loss accelerated with each decade, exceeding 20% per decade from the 70s onward. Men showed steeper declines than women from their 40s.
The implication for a man in his late 30s or 40s is clear. The fitness you build now is the reserve you will draw on in your 60s, 70s and beyond. Starting from a higher level means you stay above the threshold needed for an independent, active life for longer.
How VO2 max is measured
Laboratory testing (the gold standard)
A true VO2 max test is done on a treadmill or stationary bike while you wear a mask connected to a metabolic cart that analyzes the air you breathe. The workload rises in stages until you reach your limit. According to Harvard Health, the test typically lasts about 10–20 minutes. You can find it at sports medicine clinics, university exercise labs and some performance centres.
Wearable estimates (convenient but approximate)
Garmin, Apple, Whoop and other devices estimate VO2 max from your heart rate, pace or power, and personal data. They do not measure oxygen directly.
- A 2022 meta-analysis in Sports Medicine found that devices using exercise data were accurate on average across groups, but individual readings could be off by roughly 10 ml/kg/min in either direction. Algorithms based on resting data tended to overestimate and were less precise.
- A 2025 validation study of the Apple Watch found it underestimated lab-measured VO2 max by about 6 ml/kg/min on average, with an average error of around 13%.
- Mayo Clinic advises that wearables are not yet a reliable substitute for lab testing.
The practical takeaway: use your watch to track the direction of change over months, under consistent conditions (same sport, outdoor runs with GPS, accurate heart rate). Do not treat the exact number as a diagnosis.
VO2 max fitness categories for men
The table below shows approximate ratings for men based on normative data from The Cooper Institute (as published in Garmin’s device documentation). Different labs and populations produce somewhat different norms, so treat these as rough guides rather than precise cut-offs.
| Rating (men) | Age 30–39 | Age 40–49 | Age 50–59 |
|---|---|---|---|
| Superior | 54.0+ | 52.5+ | 48.9+ |
| Excellent | 48.3–53.9 | 46.4–52.4 | 43.4–48.8 |
| Good | 44.0–48.2 | 42.4–46.3 | 39.2–43.3 |
| Fair | 40.5–43.9 | 38.5–42.3 | 35.6–39.1 |
| Poor | Below 40.5 | Below 38.5 | Below 35.6 |
Values in ml/kg/min. Approximate; adapted from Cooper Institute normative data.
Wherever you sit today, the Mandsager data suggest the biggest gains in risk reduction come from moving out of the lowest category. You do not need to be elite to benefit.
How to raise your VO2 max
VO2 max improves with consistent training. Mayo Clinic notes that cardio three to four days a week can raise it by roughly 20–30% over three to six months, though people who start fitter usually have less room to improve.
The most time-efficient structure combines two ingredients.
1. Zone 2: your aerobic base
“Zone 2” is a popular label for steady, easy-to-moderate effort. A simple way to find it is the CDC’s talk test: at moderate intensity you can talk, but you cannot sing. You should finish feeling you could have kept going.
- Good options: brisk uphill walking, easy cycling, light jogging, rowing, swimming or the elliptical.
- Aim for sessions of 30–60 minutes, two or three times a week.
- This work builds the foundation, is easy to recover from and does not interfere much with your strength training.
2. High-intensity intervals: the VO2 max driver
Hard intervals push your heart and lungs close to their limit, which is the most direct stimulus for raising VO2 max. A 2015 meta-analysis by Milanović and colleagues found that both continuous endurance training and high-intensity intervals produced large VO2 max gains in healthy adults, with intervals giving a modest extra advantage.
The best-known protocol is the Norwegian 4×4, studied by Helgerud and colleagues in 2007:
- Warm up for about 10 minutes at an easy pace.
- Work for 4 minutes at 90–95% of your maximum heart rate, a hard effort where you can only say a few words.
- Recover for 3 minutes of active, easy movement (around 70% of maximum heart rate).
- Repeat four times, then cool down.
In that eight-week study, men doing the 4×4 three times a week improved VO2 max by about 7%, more than groups doing longer, steady sessions with matched total work. For busy men, one 4×4 session a week alongside zone 2 work is a strong, sustainable starting point.
Use whichever machine suits you: running uphill, a bike, a rower or an air bike all work. If you are new to hard training, start with shorter intervals or fewer rounds and build up over several weeks.
A sample week: 3–4 hours total
This plan fits cardio around two or three strength sessions. If you are also trying to lose fat, pair it with our guide on how to lose fat without losing muscle after 35.
| Day | Session | Time | Intensity |
|---|---|---|---|
| Monday | Strength (full body) | 45–50 min | Challenging lifts, 1–3 reps in reserve |
| Tuesday | Zone 2 cardio | 40–45 min | Easy: can talk, cannot sing |
| Wednesday | Strength (full body) | 45–50 min | Challenging lifts |
| Thursday | Norwegian 4×4 intervals | 35–40 min incl. warm-up | Hard: 90–95% max heart rate in work bouts |
| Friday | Rest or easy walk | — | Recovery |
| Saturday | Long zone 2 (ideally outdoors or with family) | 45–60 min | Easy, conversational |
| Sunday | Rest, or optional third strength session | 0–45 min | Recovery |
That totals about 3.5–4 hours, depending on how long you train. Short on time? Keep the two strength sessions and the 4×4, and fit one zone 2 session in wherever you can.
This structure lines up with the World Health Organization guidelines for adults: 150–300 minutes of moderate activity or 75–150 minutes of vigorous activity per week, plus muscle-strengthening work on two or more days. For lifting basics, see our guide to strength training after 35.
What progress to expect with VO2 max after 35
- Weeks 1–4: sessions feel easier and your heart rate at a given pace starts to drop. Your watch estimate may barely move.
- Weeks 6–12: measurable VO2 max gains are typical in previously untrained or lightly trained people. Across the trials pooled by Milanović and colleagues, both training styles raised VO2 max by roughly 5 ml/kg/min on average compared with no exercise.
- Months 3–6 and beyond: gains continue but slow. Change one variable at a time, such as adding a few minutes to zone 2 or an extra interval, and keep consistency high.
Genetics shape both your starting point and how strongly you respond, so compare yourself only with yourself. Remember that weight loss also raises a bodyweight-scaled VO2 max.
Safety note: High-intensity intervals place real demands on your heart. If you have been inactive, have a known heart, metabolic or kidney condition, or have symptoms such as chest pain or pressure, unusual breathlessness, dizziness, fainting or palpitations, see your doctor before starting vigorous exercise. The American College of Sports Medicine’s screening guidance weighs exactly these factors. Build up gradually, and stop exercising and seek care immediately if symptoms appear during a session.
Common mistakes
- Making every session medium-hard. Keep easy days truly easy so you can push the interval day properly.
- Doing intervals every day. One or two hard sessions a week is plenty for most busy men.
- Dropping strength training. Muscle and aerobic fitness both matter for healthy ageing; you need both.
- Obsessing over your watch number. Track the trend, along with how you feel and your resting heart rate.
- Inconsistent weeks. Three months of steady training beats three weeks of heroic effort.
FAQ
What is a good VO2 max for a man over 35?
Using Cooper Institute norms, a man aged 40–49 with a VO2 max of roughly 42–46 ml/kg/min rates as “good,” and above about 46 rates as “excellent.” Values vary by lab and population, so use these as approximate guides.
Can you raise VO2 max after 40?
Yes. Aerobic capacity remains trainable throughout adulthood. Consistent zone 2 work plus weekly intervals can produce meaningful gains, particularly if you are starting from a lower base.
Is zone 2 enough on its own?
Zone 2 alone will improve your fitness, especially if you are currently inactive. But adding a weekly high-intensity session is the most time-efficient way to push VO2 max further once you have a base.
How accurate is my Garmin, Apple Watch or Whoop?
Good enough to show trends, not precise enough for a single reading to be trusted. Research shows individual estimates can be off by several ml/kg/min or more. A lab test is the only way to know your true number.
Will cardio hurt my strength gains?
At three to four hours a week, mostly easy, it is unlikely to hold you back meaningfully. Separate hard leg sessions from interval days where possible, and prioritize sleep and protein.
Keep reading
Free tools: estimate your VO2 max and fitness age with the fitness age calculator, then find your training range with the zone 2 heart rate calculator.
Sources
- Mandsager K, et al. Association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing. JAMA Netw Open. 2018.
- Kodama S, et al. Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: a meta-analysis. JAMA. 2009.
- Ross R, et al. Importance of assessing cardiorespiratory fitness in clinical practice: a case for fitness as a clinical vital sign (AHA scientific statement, summary). Circulation. 2016.
- Fleg JL, et al. Accelerated longitudinal decline of aerobic capacity in healthy older adults. Circulation. 2005.
- Mayo Clinic News Network. Mayo Clinic Q&A: What does a VO2 max have to do with overall fitness?
- Harvard Health Publishing. VO2 max: What is it and how can you improve it?
- Molina-Garcia P, et al. Validity of estimating the maximal oxygen consumption by consumer wearables: a systematic review with meta-analysis and expert statement of the INTERLIVE network. Sports Med. 2022.
- Lambe R, et al. Investigating the accuracy of Apple Watch VO2 max measurements: a validation study. PLoS One. 2025.
- Garmin / The Cooper Institute. VO2 max standard ratings.
- Helgerud J, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007.
- Milanović Z, Sporiš G, Weston M. Effectiveness of high-intensity interval training (HIT) and continuous endurance training for VO2max improvements: a systematic review and meta-analysis of controlled trials. Sports Med. 2015.
- Centers for Disease Control and Prevention. How to measure physical activity intensity.
- World Health Organization. What is the recommended amount of physical activity?
- Riebe D, et al. Updating ACSM’s recommendations for exercise preparticipation health screening. Med Sci Sports Exerc. 2015.
This article is for general education and is not medical advice. Check with your doctor before starting a new training or nutrition plan, especially if you have a health condition.
