What Is a Good VO2 Max for a 40 Year Old?

Reference VO2 max percentiles for men and women aged 40 to 49, how to read a reading against them, how far wearable estimates can move it, and what the evidence links to changing it.

For a man in his 40s, the median VO2 max is 37.8 ml/kg/min. A reading of 45.0 reaches the 75th percentile, which ACSM labels Good, and 52.1 reaches the 90th, which it labels Excellent. For a woman in her 40s the median is 26.7, with 32.4 at the 75th percentile and 38.4 at the 90th. Those are the American College of Sports Medicine reference values, built from maximal treadmill tests with direct gas analysis. Two things change where a reading lands on them. The reference matters: the largest US fitness registry revised its treadmill standards down by 1.5 to 4.6 points in 2022. And a watch estimate is not a lab test: in published validation work, individual watch readings have landed more than 10 points away from the lab figure.

The full VO2 max percentile table for your 40s

The table gives every published breakpoint for the 40 to 49 band, not only the median. Find your sex, then find the two rows your number falls between.

How the 40s compare with the decade either side

The median for men falls from 42.4 in the 30s to 37.8 in the 40s and 32.6 in the 50s. For women it falls from 30.2 to 26.7 and then 23.4. So a man who holds a VO2 max of 42 from his 30s into his 40s moves from about the median of the younger band to between the median and the 75th percentile of the older one without his fitness changing at all. The ladder moves under him.

The size of that step is consistent with the largest US dataset. Across 22,379 laboratory tests in apparently healthy adults, the median fell by an average of 13.5 percent, or about 4.0 ml/kg/min, per decade on treadmill tests. The same update came out 1.5 to 4.6 ml/kg/min lower than its own 2015 standards for treadmill testing, which is why a percentile depends partly on which reference it is read against (Mayo Clinic Proceedings, 2022). Our VO2 max by age page has every decade side by side.

Why a watch reading can land in the wrong row

In the 40s, about 6 points separates the 25th percentile from the median for men (31.9 against 37.8), and the median from the 75th percentile for women (26.7 against 32.4). Watch errors in published tests are about that size or larger.

In 30 people, Apple Watch underestimated VO2 max by 6.07 ml/kg/min on average, with a mean absolute percentage error of 13.31 percent (PLOS One, 2025). In 34 people, Google Pixel Watch 3 was close on average, a bias of 0.53, but individual readings ranged from 12.56 below the lab value to 11.50 above it (PLOS One, 2026). In 19 people, a Garmin fēnix 6 showed a mean absolute percentage error of 7.05 percent (Sensors, 2025). All three studies were small. KnowYourPrime's VO2 max desk rates consumer wearable VO2 max accuracy as Emerging, and how wearables estimate VO2 max explains where the error comes from.

The practical reading is that a watch is better at showing your own trend than at placing you precisely in a percentile row.

What sitting in the bottom quarter is associated with

In 122,007 adults referred for treadmill testing, average age 53, death during follow-up was inversely related to fitness measured against their own age and sex. Those below the 25th percentile had about five times the adjusted mortality of the fittest group, a hazard ratio of 5.04. Being below average rather than above average carried a hazard ratio of 1.41, the same as smoking (1.41) and about the same as diabetes (1.40), and no upper limit of benefit was observed (JAMA Network Open, 2018).

Two limits matter. These were patients sent for a clinical exercise test, not a random sample, and fitness was estimated from treadmill workload rather than measured gas exchange. And it is an association, which does not show that moving up the ladder delivers the same difference in risk. The broader link between fitness and mortality is one of the most consistent in the field, and our desk rates it Established. More on that in VO2 max and longevity.

What moves the number in your 40s

Across 38 randomised trials in 1,682 middle-aged and older adults, aerobic training raised VO2 max by 1.80 ml/kg/min more than resistance training did, while resistance training did better for lean body mass (Archives of Gerontology and Geriatrics, 2024). Our desk rates that comparison Emerging. The two are not alternatives for most purposes, and whether strength training improves VO2 max covers the detail.

For people starting from inactivity, short bouts count. A review of 11 randomised trials found that structured bouts of five minutes or less, done at least twice a day, improved cardiorespiratory fitness in inactive adults, with moderate certainty of evidence (British Journal of Sports Medicine, 2026). See short exercise bursts and VO2 max.

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