Bruce Protocol METs Calculator
With our Bruce Protocol METs calculator, you'll learn everything you need to know about the Bruce protocol stress test. It is a non-invasive stress test to assess cardiovascular fitness and aerobic endurance or detect weak heart conditions. This article also explains the concepts of the metabolic equivalent of task and how to interpret your treadmill test results.
What is a metabolic equivalent of task (MET)?
Before we dive deeper into the Bruce protocol METs calculator, we first have to understand what a metabolic equivalent of task is. METs is a unit that estimates the energy used by our body during physical activity, which is measured in calories. One MET is defined as:
- 1 kilocalorie per kilogram of body weight per minute of activity (kcal/kg/min); or
- 3.5 milliliters of oxygen per kilogram of body weight per minute of activity (ml/kg/min).
Due to their standardized nature, METs can be used to compare activities over a range of body weights and intensities. As we see in the definition, METs is directly related to the amount of oxygen our body needs and, therefore, the often used metabolic measure VO2, or sometimes the VO2 max.
One MET equals the energy cost of sitting quietly. The more demanding the physical task is, the more oxygen your body consumes, and the higher the METs:
- Under 3 METs: Light-intensity activity
- 3–6 METs: Moderate-intensity activity
- Over 6 METs: Vigorous-intensity activity
What is the Bruce protocol stress test?
The Bruce protocol METs calculator allows you to interpret the results of the Bruce protocol stress test. Also known as the exercise tolerance test, it is used to estimate endurance athletes' overall fitness or to detect weak heart conditions. By gradually increasing the intensity of the physical activity, a person's maximum METs is measured.
Cardiologist Robert A. Bruce developed the test in 1963 as a non-invasive test to examine patients with suspected heart disease, such as a previous heart attack or a ventricular aneurysm. Even early signs of coronary artery diseases in healthy patients can be detected. For subjects with existing or suspected heart diseases, this test should only be performed under medical supervision.
Additionally, the test can measure an athlete's capacity to perform sustained exercise. It finds the maximum METs and VO2 an athlete can maintain in physical exercise.
The stages of the Bruce protocol
| Stage | Minutes | Incline (%) | Speed (mph) | Speed (km/h) | METs |
|---|---|---|---|---|---|
| 1 | 3 | 10 | 1.7 | 2.7 | 3 |
| 2 | 3 | 12 | 2.5 | 4.0 | 4–5 |
| 3 | 3 | 14 | 3.4 | 5.5 | 7 |
| 4 | 3 | 16 | 4.2 | 6.8 | 10 |
| 5 | 3 | 18 | 5.0 | 8.0 | 14 |
| 6 | 3 | 20 | 5.5 | 8.9 | 17 |
| 7 | 3 | 22 | 6.0 | 9.7 | 21 |
The runner exercises on a treadmill with the activity intensity increasing gradually. Every 3 minutes, the treadmill's speed and inclination are raised, for a maximum of 7 stages. A pulse watch or an electrocardiograph (ECG) monitor the runner's heart rate. The Bruce protocol stress test ends when the subject cannot continue due to fatigue, or the medical staff decides to end it due to blood pressure or heart rate values going beyond healthy limits.
Formulas used in this calculator
The maximum heart rate is determined with the Oakland non-linear formula:
Max heart rate = 192 − (0.007 × age²)
The maximum METs value is then defined as:
For women: METsmax = (4.38 × T − 3.9) / 3.5
For men: METsmax = (14.8 − (1.379 × T) + (0.451 × T²) − (0.012 × T³)) / 3.5
where T is the time (in minutes) the subject spent on the treadmill.
The maximum oxygen volume VO2 max is then:
VO2max = METsmax × 3.5
Note: This calculator is not suitable for interpreting the results of the modified Bruce protocol stress test. Please consult a medical expert in that case.
What are good maximum METs values?
The maximum METs a person can achieve depends heavily on age and gender. On average, men have larger hearts than women, therefore pumping more blood through the body, providing oxygen to the muscles. Furthermore, the maximum METs peaks naturally in the 20s, and from this point on declines by 10% per decade.
- Average non-trained women have a maximum METs of around 8 and non-trained men 10.
- A good maximum METs value for a 30-year-old woman is 14 and for a man 15.
- Elite athletes can reach maximum METs of up to 22 (women) and 25 (men).
How to use the Bruce Protocol METs calculator?
- Select your unit system — American (Imperial) for mph and lbs, or Metric for km/h and kg.
- Select your gender — the formula differs for men and women.
- Enter your age — used to calculate your maximum heart rate.
- Enter your treadmill time — the total time you lasted on the treadmill in minutes (e.g., 12.5 for 12 minutes 30 seconds).
- Enter your body weight (optional) — for context.
- Click Calculate METs to see your results.
Why is this relevant for me?
A scientific article from 2018 found that cardiorespiratory fitness measured via VO2 max (and therewith also max METs) "has been shown to be a strong and independent predictor of all-cause and disease-specific mortality." Poor cardiorespiratory fitness is directly associated with a higher risk of cardiovascular disease and cancer.
To provide a reference on how much you should exercise, the WHO recommends 150 to 300 minutes of moderate to vigorous aerobic activity per week for all adults.
Do not fret if your current maximum METs is not perfect — you can easily increase it with a good training schedule. And a massive share of athletic performance depends on technique and experience, not just METs.
FAQs
What is a good METs score for my age?
A good METs score varies by age and gender. For a 30-year-old, a good score is around 14 METs for women and 15 METs for men. Values above 17 are considered excellent for most age groups.
Can I use this calculator for the modified Bruce protocol?
No. The modified Bruce protocol adds two extra stages at the beginning (0% and 5% incline at 1.7 mph). The formulas here apply only to the standard Bruce protocol.
How does METs relate to VO2 max?
VO2 max (ml/kg/min) = METs × 3.5. One MET equals approximately 3.5 ml/kg/min of oxygen consumption.
Should I take the Bruce protocol test without medical supervision?
Healthy adults without known heart disease can generally take the test safely. However, if you have suspected or known heart conditions, always perform the test under medical supervision.