VO2max and Mortality: What the 2024-2025 Data Added

VO2max is the maximum volume of oxygen the body can take up and deliver to the muscles per minute of work. It is an integrated measure of how the heart, lungs, blood vessels, and mitochondria perform, and at the same time one of the strongest known predictors of lifespan. The link itself — "higher fitness, lower mortality" — is no news: it was shown back in the 1990s. What is more interesting is what the large studies of 2024-2025 added to this classic picture.

What the classics said

A reference point for understanding the "ceiling" of the benefit is the Cleveland Clinic study published in JAMA Network Open in 2018. The authors analyzed 122,007 patients who underwent a treadmill exercise test. The conclusion was stark: the link between fitness and survival had no upper limit — the higher the fitness, the lower the mortality, with no point of saturation.

The numbers in that work sound almost unbelievable. People with the lowest fitness had a risk of death five times higher (HR 5.04) than the elite group. For comparison: smoking raised the risk in the same sample by 1.41 times, and diabetes by 1.40. In other words, low cardiorespiratory fitness hit survival harder than the classic risk factors everyone fears.

What the 2024-2025 data added

The main contribution of the new work is not a fresh sensation but scale and rigor. In 2024, the British Journal of Sports Medicine published an overview of meta-analyses that pooled 199 unique cohorts and more than 20.9 million observations. On this huge base a clear dose-response relationship was confirmed: every additional 1 MET of fitness lowered the risk of death from any cause by 11-17%, and the risk of heart failure by 18% per MET.

In a direct comparison of the extreme groups, people with high fitness had a risk of death 53% lower than those with low fitness (HR 0.47). This is not the conclusion of one team on one sample — it is a consistent signal from hundreds of cohorts around the world.

The second important addition is a 2025 study in the Journal of Sport and Health Science (42 studies, 35 cohorts, 3.8 million observations). It showed that fitness assessed with simple tests — submaximal exercise or even estimation formulas with no gas analyzer — predicts mortality almost as accurately as the "gold standard" with a lab-measured VO2max. The risk reduction per MET was 14% for all-cause mortality (RR 0.86) and 16% for cardiovascular mortality (RR 0.84).

Who gets the largest gain

This is the most practical conclusion, and it runs counter to intuition. Most people assume the winners are those who are already in good shape. In reality the largest relative gain in survival goes to those who start from the very bottom.

Steven Blair's classic study (JAMA, 1995) followed men who changed their fitness level between two examinations. Those who moved from the "unfit" category to the "fit" one cut their risk of death by 44% compared with those who stayed unfit. In absolute terms, mortality fell from 122 cases per 10,000 person-years among the consistently untrained to 67.7 among those who improved. Every extra minute on the treadmill between examinations meant a 7.9% drop in risk.

The logic is simple: the "fitness versus risk" curve is steepest at its very base. Moving from a very low level to merely low saves more lives per unit of effort than moving from good to excellent. For someone who is not training now, the first weeks of regular aerobic exercise are the most profitable investment in survival there is.

And what about VO2max genetics

Here it is important not to confuse two things. VO2max really does respond differently to training in different people. In the HERITAGE study, with an identical 20-week program, the average gain was 400 ml/min, but the individual spread was colossal — from -114 to +1097 ml/min. About 47% of this difference in responsiveness is explained by heredity. There are "high responders" and "low responders."

But it does not follow that training is useless for "low responders." A drop in mortality from regular exercise is seen even in those whose VO2max grows modestly: peripheral adaptations, blood-pressure control, and glucose metabolism all work too. Genetics determines how steeply your personal curve will rise — but it does not cancel out the fact that it will rise. The meaningful comparison is yourself against yourself six months ago, not your VO2max against someone else's.

How much that is in training

None of this work calls for marathon volumes. One MET is roughly the difference between "I can barely move" and "I can manage a brisk walk uphill." The baseline recommendations that evidence-based medicine agrees on are around 150 minutes of moderate aerobic exercise a week, plus a little higher-intensity interval work for those who are ready. For an untrained person, even regular brisk walks shift them into exactly that part of the curve where the most lives are saved.