If you’ve ever trained for a race, pushed through a brutal workout, or even just climbed a flight of stairs and wondered “Why does this feel so hard?”—you’ve brushed up against your VO₂ max.  If you’ve never heard of it before, don’t worry. Most people haven’t.
But here’s the truth: VO₂ max is one of the single most important metrics for your health and longevity.

What is VO₂ max?

VO₂ max stands for “maximal oxygen uptake” which is basically, how efficiently your body can take in, transport, and use oxygen during intense exercise. It’s a measure of your cardiorespiratory fitness, and it's one of the strongest predictors we have for:

• Performance (how long and hard you can go)
• Recovery (how quickly you bounce back)
• Longevity (how long—and how well—you’ll live)

Studies have consistently demonstrated that even modest improvements in VO₂ max can lead to significant reductions in the risk of chronic disease and premature death. In fact, VO₂ max is a more powerful predictor of long-term health outcomes than traditional markers such as cholesterol levels, blood pressure, smoking status, or body mass index (BMI).

A pivotal study by Mandsager et al., published in JAMA Network Open, examined the relationship between cardiorespiratory fitness and all-cause mortality. The findings revealed that individuals in the lowest fitness percentile (below the 25th percentile) faced a more than fivefold increase in the risk of all-cause mortality compared to those in the highest fitness group (97.7th percentile and above). The association between fitness level and mortality was both continuous and graded, with no upper limit at which additional fitness ceased to be beneficial. Importantly, even incremental gains in fitness percentile were linked to substantial reductions in mortality risk. These effects were consistent across various age groups and between sexes.

These findings are further supported by multiple large-scale cohort studies, which have shown a strong and consistent relationship between higher VO₂ max percentiles and lower risks of both all-cause and cardiovascular mortality across diverse populations, including variations in age, sex, and race.¹

Why does it matter?

VO₂ max is trainable, but if you don’t measure it, you’re just guessing. A lab-quality VO₂ max test tells us exactly where your aerobic capacity stands, revealing your:

• Aerobic thresholds (your specific actual measured training zones)
• Fat vs. carbohydrate utilization (how your body burns fuel at different intensities)
• Efficiency and ventilatory response (how well you breathe and recover)

This is the gold for anyone who wants to train smarter, prevent overtraining, avoid injury, and stay metabolically flexible as they age.

_Sources:

_{VO2max and Mortality}

_{1. Mandsager K, Harb S, Cremer P, Phelan D, Nissen SE, Jaber W. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Netw Open. 2018 Oct 5;1(6):e183605. doi: 10.1001/jamanetworkopen.2018.3605. PMID: 30646252; PMCID: PMC6324439.}