Measuring VO2max on stationary bike

Question

Have collected some data points in measuring VO2max over a few years using two methods: non-exercise and stationary bike (2min warmup + 6min at constant heartrate). The latter is supposed to be more accurate, but a couple things stand out:

1. The variability in the stationary bike method is far higher than what I would expect, even when discounting for the fact that it only returns integer values.
2. Stationary bike method underestimates my VO2max compared to non-exercise method.

The non-exercise method adjusts for age, weight, gender and depends on a self-assessment score and is ultimately more of a marker-in-the-sand value. Now, the true VO2max will depend on many factors, but ceteris paribus (apart from age), is anybody familiar with the poor accuracy of a VO2max measurement using a stationary bike + chest-worn heartrate monitor?

Answer 1

First, it is worth noting that non-exercise tests are especially inaccurate at determining both VO₂max and changes thereto. One study examining a host of different methods, including that described by Jackson (1990), concluded:

"changes to [estimated cardiorespiratory fitness] (eCRF), as determined using non-exercise prediction equations, were significantly associated with changes in directly measured [cardiorespiratory fitness] (CRF). However, changes in eCRF values from most of the prediction equations were significantly different from the changes in directly measured CRF. Furthermore, all of the prediction equations had a low degree of accuracy when identifying even the directional change of CRF. These findings highlight the errors associated with non-exercise prediction equations, especially related to monitoring longitudinal changes, and suggest limited prognostic utility of eCRF within a clinical setting."

Exercise VO₂max tests are therefore more accurate, but without knowledge of the precise method employed by your stationary bicycle, it is impossible to assess its accuracy and/or limitations.

In sporting circles, VO₂max is typically tested directly with a multi-stage maximal test, but this requires specialised equipment and tester expertise. In the field, this can be replaced with a multi-stage submaximal test, such as the YMCA Submaximal Cycle Ergometer Test, which estimates VO₂max through extrapolation from submaximal efforts. Intervals are typically three to five minutes, since a maximal three-minute effort is around 95% aerobic and a four-minute effort around 99% aerobic.

I hope that helps, even though I can not give you more information about your particular stationary bicycle.

Answer 2

For cycling and running, your VO2max can be estimated from either average power or distance ran during a short maximal effort (3 to about 12 minutes).

In cycling, you require an accurate power meter or smart trainer. The former measures the amount of torque you apply to the crankarms, and converts this to power. Smart trainers measure the same concept at the trainer's flywheel. Some gyms have Stages bikes, which produce credible power meters but which is going out of business. In this answer on the Bicycles Stack Exchange, I discussed some methods, but briefly, you warm up, then you do an all-out 5 minute effort. You can then use the following equation:

VO2max in L/min = 0.0108 x power (W) + 0.007 x body mass (kg)

Note that the output is in liters, not the usual milliliters (mL), and it is not normalized to body mass. Alternatively, if you're on Zwift, if you do a short (I think 3-6 minute) maximal effort, it will estimate your VO2max using a similar formula (I got similar results from both formulas).

There probably are other similar formulae out there. Note that in all cases where you use a formula like this, there is some prediction error. For example, in the other answer, one different cycling prediction equation (this using maximal power from a ramp test, which you can conduct on a cycling smart trainer), the equation should predict VO2max for most fit men within a range of 8.32 mL O2/min kg overestimate or 15.52 unit underestimate, with most people falling closer to their actual value. Not all formulas have their prediction errors estimated. You might find these in peer-reviewed papers, but it can be hard to search.

Running power is not widespread as there's no specific thing that they can mount strain gauges to. However, you can estimate VO2max from distance covered in a maximal effort, probably better in a more controlled setting like a track. One example is the Cooper Test, a 12-minute maximum run. Where d is the distance covered in meters, a VO2max estimate is

(d - 504.9) / 44.73

With all such tests, pacing is important, and beginners may not know how to pace a maximal effort. A mis-paced effort should tend to under-estimate your true VO2max. I suspect the issue is a bit worse for longer efforts. Not being used to pushing yourself to the max will also tend to produce under-estimates.

One can imagine other sports like maybe indoor rowing where you could conceivably get a VO2max estimate. Interested parties should check the peer-reviewed literature or Google. There may be the issue of variations between equipment to consider, which might throw off the estimate.

Last, VO2max tests are increasingly available. One lab near me charges $3-400 for a VO2max test plus some other tests that may be useful for some sports. The local university sports science lab charges less. Readers can determine for themselves if this is worth the cost. Readers who are serious endurance athletes might not want to spend that money; their VO2max is very likely to be above average, and while VO2max is very strongly linked to mortality, the returns are diminishing. It is very important to avoid having a low or very VO2max. However, if your aerobic fitness is very low, then essentially anything is likely to improve it. Walking 10 minutes a day is likely to help someone who's literally starting from the couch. Naturally, you need to overload progressively to keep increasing your fitness. The point is that you may not necessarily need to quantify your VO2max to motivate yourself to keep progressing. You could consider assessing yourself by things like what's the longest hike or bike ride I did this year.