What this calculator does
The Bruce protocol is a graded treadmill test where speed and gradient both increase every three minutes until the subject cannot continue. Time to exhaustion is then converted to an estimated VO₂max through a regression equation fitted to measured values.
Twelve minutes on the treadmill estimates about 42.5 ml/kg/min for a man and 48.7 for a woman, and the two equations differ because they were fitted to separate samples rather than because the underlying physiology differs that way. These are estimates from a time, not measurements of oxygen uptake, and individual results scatter around them considerably.
The formula
For men the equation is a cubic in treadmill time: 14.8 − 1.379T + 0.451T² − 0.012T³. For women it is linear: 4.38T − 3.9. T is time in minutes to exhaustion. The METs figure divides the VO₂max by 3.5, since one MET is defined as 3.5 ml of oxygen per kg per minute.
| Term | Meaning |
|---|---|
| VO₂max | Maximal oxygen uptake in ml per kg per minute, the standard measure of aerobic capacity. |
| Bruce protocol | A graded treadmill test raising speed and incline every three minutes. |
| MET | Metabolic equivalent, defined as 3.5 ml/kg/min, roughly resting metabolic rate. |
| Regression estimate | A value predicted from a formula fitted to measured data rather than measured directly. |
The inputs explained
| Field | What to enter |
|---|---|
| Time on treadmill (min) | Time on the treadmill in minutes, to the point of volitional exhaustion. |
| Sex | Sex, which selects the equation. The two were fitted separately and are not interchangeable. |
When to use it
Estimating fitness without gas analysis
Direct VO₂max measurement needs a metabolic cart and a laboratory. A treadmill and a stopwatch give an estimate that is good enough to track change over time.
Tracking training progress
Repeating the same protocol some months apart gives a comparable figure, and the change is more meaningful than the absolute value.
Converting to METs for exercise prescription
Exercise intensities are often prescribed in METs, and the conversion from VO₂max is a straight division by 3.5.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What VO2max does each treadmill time estimate?
A range of times to exhaustion on the Bruce protocol.
| Time to exhaustion | Estimated VO₂max | In METs |
|---|---|---|
| 6 min | 20.2 ml/kg/min | 5.76 |
| 9 min | 30.2 ml/kg/min | 8.62 |
| 12 min | 42.5 ml/kg/min | 12.13 |
| 15 min | 55.1 ml/kg/min | 15.74 |
Questions
How accurate is the Bruce protocol estimate?
It correlates well with measured VO₂max across a population but individual estimates can be off by 10% or more. The equation cannot see running economy, motivation or whether the subject genuinely reached exhaustion, all of which affect the time. Treat it as a fitness indicator rather than a measurement.
Why are the male and female equations different shapes?
Because they were fitted separately to separate samples, and the cubic simply fitted the male data better than a line did. It is a statistical artefact of the fitting rather than a claim about physiology, which is one reason to treat both as approximations.
What is a good VO2max?
It depends heavily on age and sex. Roughly, 35 to 45 ml/kg/min is average for a man in his thirties and 30 to 38 for a woman. Trained endurance athletes commonly exceed 60, and elite ones considerably more. Comparing against age-matched norms is more informative than an absolute figure.
Is a maximal treadmill test safe?
It is a maximal exertion test, which carries real risk for anyone with undiagnosed cardiovascular disease. Clinical versions are supervised with ECG monitoring for that reason. Anyone with known heart problems, symptoms on exertion, or who is not already exercising regularly should speak to a doctor before attempting it.
For a running-based VO₂max estimate instead, see the VO2max from running calculator. For calories from heart rate, see the calories burned by heart rate calculator.