VO2 max, and the part of the curve you control

In 122,007 patients, elite cardiorespiratory fitness was associated with 80% lower mortality than low fitness. No upper limit of benefit was observed.

By Hydra Editorial

In 122,007 patients who underwent treadmill testing, those in the elite fitness category had an 80% lower adjusted risk of death than the least fit group over a median 8.4 years. The authors found no upper limit above which extra fitness stopped helping. VO2 max declines with age, and the slope is the part that responds.

Mandsager and colleagues, published in JAMA Network Open in 2018, followed 122,007 patients for a median 8.4 years, covering 1.1 million person-years and 13,637 deaths.

Compared with the low-fitness group, adjusted hazard ratios for all-cause mortality were 0.71 for below average, 0.50 for above average, 0.30 for high and 0.20 for elite. Even elite versus high fitness showed a further reduction (HR 0.77).

For scale, the same analysis reported hazard ratios of 1.41 for smoking, 1.40 for diabetes and 1.29 for coronary artery disease. The gap between low and elite fitness was larger than any of them: low fitness carried a hazard ratio of 5.04 against elite. The authors concluded there does not appear to be an upper limit of aerobic fitness above which a survival benefit is no longer observed.

This was an observational cohort of patients referred for treadmill testing, not a general population sample, so it shows association, and reverse causation (people are less fit because they are unwell) cannot be fully excluded.

Can you change your VO2 max after 40?

VO2 max declines with age in most people, but the often-quoted “10% per decade” is a simplification that fits almost nobody. Longitudinal data from the Baltimore Longitudinal Study of Aging, following 435 men and 375 women aged 21 to 87, found the decline accelerates: roughly 3 to 6% per decade in the twenties and thirties, rising above 20% per decade after 70.

The slope is also not fixed. Trained adults show a shallower curve, and the largest absolute risk reductions in the Mandsager data came from moving out of the bottom category, not from reaching the top of it.

That is the useful framing. The difference between low and below-average fitness carried a hazard ratio of 0.71, which is a meaningful shift available to the people furthest from athletic, and one that tracking the trend rather than the number makes visible.

One caveat on measurement: wearable VO2 max is an estimate derived from heart rate and pace, not a gas-exchange measurement, and its absolute accuracy is limited. Its consistency over time is better than its precision at any single point, which makes the trend more trustworthy than the number.

The bottom line

  • In 122,007 patients, elite fitness was associated with an 80% lower adjusted mortality risk than low fitness (HR 0.20).
  • The low-versus-elite fitness gap exceeded the hazard ratios reported for smoking, diabetes and coronary artery disease in the same analysis.
  • Decline is not linear: longitudinal data show roughly 3 to 6% per decade in early adulthood, accelerating past 20% per decade after 70.

Frequently asked questions

What is a good VO2 max for my age?
Published percentile charts group by age and sex, but the mortality evidence is about relative position rather than any absolute figure. In the Mandsager cohort, each step up the fitness distribution was associated with lower mortality risk, with the steepest change occurring between the lowest and second-lowest categories.
How accurate is the VO2 max on my watch?
It is an estimate, not a measurement. Wearables infer VO2 max from the relationship between heart rate and pace, which laboratory gas-exchange testing measures directly. Absolute values can be off by a meaningful margin, though the direction of change over months is generally more reliable.

Sources

  1. Mandsager, K., Harb, S., Cremer, P., Phelan, D., Nissen, S.E. and Jaber, W., 2018. Association of Cardiorespiratory Fitness With Long-term Mortality Among Adults Undergoing Exercise Treadmill Testing. JAMA Network Open, 1(6), e183605.
  2. Fleg, J.L., Morrell, C.H., Bos, A.G., Brant, L.J., Talbot, L.A., Wright, J.G. and Lakatta, E.G., 2005. Accelerated longitudinal decline of aerobic capacity in healthy older adults. Circulation, 112(5), 674 to 682.
Hydra Editorial

Hydra's editorial team. We write from primary research and cite every study we rely on, with its year and journal. We quantify claims wherever the evidence allows and state plainly where it does not: where a finding rests on a small or single trial, we say so in the text rather than in a footnote.