What Is VO2 Max? And What Counts as a Good Score

VO2 max is the maximum rate at which your body can take in, transport, and use oxygen during exercise. It is measured in millilitres of oxygen per kilogram of body weight per minute (mL/kg/min). What counts as good depends on your age and sex, but the short version is straightforward: at any age, getting yourself above the median for your decade meaningfully reduces all-cause mortality risk over the years that follow. The number matters more than almost any other single fitness metric in published cardiology literature, and it is also one of the most trainable.

TL;DR

What VO2 max actually is

VO2 max is the maximum rate at which your body uses oxygen during exhaustive exercise. The unit, millilitres of oxygen per kilogram of body weight per minute, captures three things at once: how much oxygen you can move per minute, your body weight (so the score is comparable across body sizes), and the time over which it is sustained.

Producing that number requires four systems working together. Your lungs have to take oxygen in fast enough. Your heart has to pump blood through the lungs and back out to working muscles fast enough. Your blood has to carry enough oxygen per litre (which depends on haemoglobin and red blood cell volume). Your skeletal muscle mitochondria have to extract and use oxygen efficiently at the cellular level. A bottleneck at any of the four caps the system. Training improves all four to varying degrees in untrained adults, which is why VO2 max is so trainable.

The integrated nature of the measurement is why it predicts so much. A single weak link (poor lung function, low cardiac output, anaemia, deconditioned muscle) shows up as a low VO2 max even if the other three systems are fine. A high VO2 max signals that all four systems are functioning at adequate or better than adequate capacity. That broad systemic signal is what makes VO2 max the single best summary measure of cardiorespiratory fitness, and it is why the mortality data on it is so robust.

What counts as a good score

The practical answer for most adults: above the 50th percentile for your age and sex band on the FRIEND registry. That is the Above Average band on the published reference standards. Below the 50th percentile is the territory where mortality risk starts to climb meaningfully. Above the 75th is the Good band, where the risk reduction compounds further. Above the 90th is the Excellent band, the upper end of the longevity dose-response curve.

Specifically, the FRIEND 50th-percentile thresholds in mL/kg/min:

Hitting those numbers puts you at roughly the median for your age and sex. Practically that means the cardiorespiratory fitness of half your peer group is below yours and half is above. It is the floor at which most cardiologists would say your cardiorespiratory fitness is in defensible shape for your decade.

For the full age-decade percentile bands (10th through 90th) for both sexes, see the VO2 max chart by age and sex. For your own personalised reading, the VO2 max calculator estimates your percentile from resting heart rate using the Uth method when you have not had a clinical test.

Why the number matters this much

The cardiology mortality literature on cardiorespiratory fitness is the strongest evidence base of any modifiable health metric. Three studies anchor it.

Mandsager 2018, JAMA Network Open. Cleveland Clinic cohort study of 122,007 adults who completed treadmill exercise testing, followed for a median of 8.4 years. Across nearly all-cause mortality, the relative risk gap between elite cardiorespiratory fitness (top 2.5 percent) and low (bottom 25 percent) was greater than the combined attributable risk of smoking, type 2 diabetes, hypertension, and end-stage renal disease in the same cohort. Translated: getting from below average to elite reduces all-cause mortality risk more than not smoking, not having diabetes, and not having coronary artery disease combined.

Kodama 2009, JAMA. Meta-analysis of 33 prospective cohort studies covering 102,980 participants. For each one-MET increase in cardiorespiratory fitness (one metabolic equivalent, roughly the difference between sitting and walking at moderate pace), the risk of all-cause mortality was 13 percent lower and the risk of cardiovascular events was 15 percent lower. The relationship was approximately linear across the range studied, with no plateau at the upper end.

Kaminsky 2015, Mayo Clinic Proceedings. The FRIEND registry paper that defines the percentile bands cited above. Published reference standards for cardiorespiratory fitness measured by treadmill cardiopulmonary exercise testing, drawn from 7,783 healthy adults at clinical exercise labs across North America.

The implication is straightforward. Of every modifiable health metric in published medicine, cardiorespiratory fitness as captured by VO2 max moves the mortality needle furthest. Smoking cessation, blood pressure control, glycaemic control, and lipid management all matter. Cardiorespiratory fitness matters more, by a margin that surprises most clinicians the first time they see the numbers.

How training changes the number

VO2 max is genuinely trainable, particularly in adults starting from low baseline. The dose-response curve is well established across the exercise physiology literature.

In previously untrained adults, 12 to 16 weeks of structured cardiovascular training (Zone 2 base building plus a small amount of high-intensity interval work) produces measurable improvements of 10 to 20 percent in the VO2 max number. That is enough to climb one full percentile band for most readers. Adults who add resistance training in parallel typically see the upper end of that range, because skeletal muscle adaptation drives mitochondrial density improvements that show up in the VO2 max measurement.

The rate of improvement slows as the trained number climbs. Going from Below Average to Above Average is the largest gain available, and it tends to land within the first 16 weeks of consistent work. Going from Above Average to Excellent is achievable but typically requires 12 to 18 months of structured training and is the realistic ceiling for most adults over 45 who were not previously athletes. Above the 90th percentile, gains are slow and require sport-specific volume.

The decline curve also matters. From your 30s onward, untrained adults lose roughly 1 percent of VO2 max per year, accelerating after 60. Trained adults flatten the curve considerably. The 60-year-old who has been training cardiovascular and strength for two decades typically has the VO2 max of an untrained 40-year-old. Two decades of biological age recovered through training is the realistic prize in the longevity literature.

How to find your own number

Three methods exist, in declining order of accuracy.

A clinical cardiopulmonary exercise test (CPET) with gas analysis is the gold standard. Treadmill or cycle ergometer, graded protocol, respiratory mask measuring inhaled and exhaled gas concentrations. Performed at sports-medicine clinics. The cost in Singapore is typically SGD 250 to 500. This is the right test for athletes and adults who already train near maximum, but it is genuinely the wrong test for most untrained adults for safety and accuracy reasons covered in VO2 max test Singapore: what most clinics get wrong.

A sub-maximal estimate from a clinical step test is the right test for the general population. Catalyst uses the YMCA 3-minute step test on the 4-Pillar Healthspan Assessment: 12-inch step, 24 steps per minute on a metronome cadence, three minutes total, followed by a 1-minute recovery heart-rate count. The result lands on the Catalyst Healthspan Report as a band, from Excellent to Poor on the same FRIEND-anchored percentile structure.

A wearable estimate from a smartwatch (Apple Watch, Garmin, Whoop, Oura) is useful for tracking your own trend over months but not adequate for an absolute benchmark. The structural error against direct measurement runs roughly 10 to 15 percent, covered in Apple Watch VO2 max vs treadmill: how wrong is yours. Use the watch for trend; use a clinical step test or the free VO2 max calculator for an absolute estimate.

Where to start

If you want a banded score across all four healthspan pillars before booking anything, the free Healthspan Audit is a 12-question self-assessment that lands a banded result across body composition, cardiorespiratory fitness, stability, and strength in your inbox in three minutes. The cardiorespiratory band uses the same FRIEND percentile structure cited above. If your audit band comes back at Average or below, the 12 to 16-week training window is the leverage point, and the in-studio 4-Pillar Healthspan Assessment measures the actual starting number you can train against.

Frequently asked questions

Q. Is the FRIEND chart valid for Singapore adults?

The FRIEND registry sample is North American (predominantly Caucasian). There is no equivalent comprehensive Singapore-specific cardiopulmonary exercise testing registry. The published literature on cardiorespiratory fitness norms across populations is consistent once adjusted for age, sex, and body composition, so the FRIEND bands are a defensible benchmark for Singapore adults. The relative percentile structure (band ordering, dose-response curve) holds across ethnic groups even where absolute thresholds may differ slightly.

Q. How much can I improve VO2 max in 16 weeks?

Previously untrained adults reliably move 10 to 20 percent on the measured VO2 max number across 12 to 16 weeks of structured training (two Zone 2 cardio sessions plus two resistance training sessions per week, with adequate recovery). That is enough to climb one full FRIEND percentile band for most readers. The largest gains come from the lowest starting points; the rate of improvement slows as the trained number climbs into the Good and Excellent bands.

Q. Does muscle mass affect my VO2 max score?

Yes, in two ways. VO2 max is scaled to body weight (mL/kg/min), so heavier adults need to use more total oxygen per minute to hit the same per-kilogram number. And skeletal muscle is itself the largest oxygen-consuming tissue at peak exercise, so muscle quality and mitochondrial density directly drive the achievable maximum. Adults who add resistance training in parallel with cardiovascular training typically see larger VO2 max improvements than cardio-only protocols. The mechanism is muscle, not just heart and lungs.

Citations

Kaminsky, L. A., Arena, R., & Myers, J. (2015). Reference Standards for Cardiorespiratory Fitness Measured With Cardiopulmonary Exercise Testing: Data From the Fitness Registry and the Importance of Exercise National Database. Mayo Clinic Proceedings, 90(11), 1515 to 1523. mayoclinicproceedings.org/article/S0025-6196(15)00532-X/fulltext

Mandsager, K., Harb, S., Cremer, P., Phelan, D., Nissen, S. E., & Jaber, W. (2018). Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Network Open, 1(6), e183605. jamanetwork.com/journals/jamanetworkopen/fullarticle/2707428

Kodama, S., Saito, K., Tanaka, S., Maki, M., Yachi, Y., Asumi, M., et al. (2009). Cardiorespiratory Fitness as a Quantitative Predictor of All-Cause Mortality and Cardiovascular Events in Healthy Men and Women: A Meta-analysis. JAMA, 301(19), 2024 to 2035. jamanetwork.com/journals/jama/fullarticle/183993