Why your VO2 max is different on every test

Key points

• VO2 max (VO2max) depends on how it was tested. The protocol, the equipment, how "max" is defined and the equation used all move the number.
• In 580 competitive cyclists, three standard equations gave group averages from 67 to 74 ml/kg/min when fed the peak power from a ramp test they were not built on. The measured average was 63.
• Each equation is sound for the test it was built on. The trouble starts when the test and the equation do not match.
• The practical rule: pick one test and one equation, and compare your result only with your own earlier results.
• Compare the equations yourself with the VO2 max calculator.

On this page: What VO2 max is · Why equations disagree · Why tests differ · What to do about it · Questions

This is part 1 of a three-part series. Part 2 covers how much error a lab test and a field test each carry. Part 3 covers what I track instead.

What is VO2 max?

VO2 max is the most oxygen your body can take in and use in a minute, usually given per kilogram of body mass (ml/kg/min). It depends on how much blood the heart can pump and how much oxygen the working muscles can extract.

It is the ceiling of aerobic performance. Lactate thresholds, critical power and race pace all sit at some fraction of it.

Why do VO2 max equations disagree?

Jurov and colleagues (2023) measured VO2 max in 580 competitive cyclists on a ramp test. Then they asked what the standard prediction equations would have said. I have added one more equation using the group averages from their paper.

Method	Men (ml/kg/min)	Women (ml/kg/min)
Measured in the lab	63.4	54.8
FRIEND equation	67.1	55.9
Storer equation	73.6	56.9
Hawley and Noakes equation*	73.9	66.4

*My calculation from the group's average peak power and body mass. The other rows are the values reported in the paper.

Read this table with two cautions. The cyclists were young, with the men averaging 17, and the equations were built on adults. And none of the equations was built on this exact test. That second caution is the lesson. Each equation is sound for its own test. Fed the peak power from another test, they disagree by up to 7 ml/kg/min in the men and 11 in the women.

The same happens with 5-minute power. For a 75 kg rider holding 300 W, the equation I use gives 49 ml/kg/min and the Sitko equation gives 52. When Borszcz and colleagues (2024) checked the Sitko equation in 49 other cyclists, it read 6.6 low on average.

Why is my VO2 max different on every test?

The protocol. Storer started at 0 W and added 15 W every minute. Hawley and Noakes started at 3.33 W/kg and used 150-second stages. Jurov started at 100 W and added 20 W every minute. A faster ramp ends at a higher power, so "peak power" is a different number in each test.

The equipment and settings. Storer's subjects rode a mechanically braked ergometer at 60 rpm. Hawley and Noakes used an electrically braked one at 80 to 90 rpm. Jurov's cyclists rode their own bikes mounted on an ergometer.

What counts as "max". Hawley and Noakes took the highest oxygen uptake over any 60 seconds. Storer used a complete 30-second interval. Jurov averaged the highest 5-second values in the last 30 seconds, and only accepted tests that showed a plateau. In Hawley and Noakes's cyclists, only 38% showed one.

The people behind the equation. Storer's equations came from sedentary adults. FRIEND came from 5,100 adults with an average VO2 max of 42 in the men. Hawley and Noakes tested trained cyclists. An equation carries its sample with it.

What should you do about it?

A single VO2 max figure tells you as much about the test as about the athlete. That does not make the number useless. It means a figure from one method cannot be compared with a figure from another.

Three habits follow from that.

1. Keep one test and one equation, and stay with them.
2. Compare your result with your own earlier results, never with a friend's number from a different test.
3. Read the power or pace you produced first. The VO2 max estimated from it is context.

The VO2 max calculator shows each equation beside the test it needs, so you can match the two.

Common questions

Why is my VO2 max different on every calculator?

Each calculator uses an equation built on one test and one group of people. A ramp-test equation, a 5-minute equation and a watch algorithm will give different values for the same athlete. In the men among 580 competitive cyclists, three standard equations averaged between 67 and 74 ml/kg/min against a measured 63.

Is my watch's VO2 max the same thing?

No. Watches estimate VO2 max from the link between heart rate and pace or power during normal training. That depends on heat, fatigue and heart rate accuracy, and it is one more method that will give its own value.

Does VO2 max still matter?

Yes, as a description of engine size and as a way to see change over time from one consistent test. It is a weak way to compare trained athletes with each other.

References:

• Jurov I, Cvijić M, Toplišek J (2023). Predicting VO2max in competitive cyclists: is the FRIEND equation the optimal choice? Front Physiol 14:987006. Free full text
• Storer TW, Davis JA, Caiozzo VJ (1990). Accurate prediction of VO2max in cycle ergometry. Med Sci Sports Exerc 22(5):704–712. Publisher page
• Hawley JA, Noakes TD (1992). Peak power output predicts maximal oxygen uptake and performance time in trained cyclists. Eur J Appl Physiol 65:79–83. Publisher page
• Kokkinos P, Kaminsky LA, Arena R, Zhang J, Myers J (2018). A new generalized cycle ergometry equation for predicting maximal oxygen uptake: the Fitness Registry and the Importance of Exercise National Database (FRIEND). Eur J Prev Cardiol 25:1077–1082. Publisher page
• Sitko S, Cirer-Sastre R, Corbi F, López-Laval I (2022). Five-minute power-based test to predict maximal oxygen consumption in road cycling. Int J Sports Physiol Perform 17(1):9–15. Publisher page
• Borszcz FK, Tramontin AF, de Lucas RD, Costa VP (2024). Is the 5-minute time-trial cycling test a valid predictor of maximal oxygen uptake? An external cross-validation study. Int J Sports Physiol Perform 19(6):565–575. Publisher page

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