The Bruce Protocol Treadmill Test for Athletes

The Bruce protocol treadmill test is used to estimate the overall fitness of endurance athletes. The test was originally designed by cardiologist Robert A. Bruce in 1963 as a non-invasive test to assess patients with suspected heart disease.

In a clinical setting, the Bruce treadmill test protocol is sometimes called a stress test or exercise tolerance test. The test can be used to estimate maximal oxygen uptake (VO2 max), which is a measure of an athlete's capacity to perform sustained exercise. It is linked to aerobic endurance.

VO2 Max Testing

Maximal oxygen uptake (VO2 max) specifically refers to the maximum amount of oxygen that an individual can take in and use during intense or maximal exercise. It is measured as milliliters of oxygen used in one minute per kilogram of body weight (ml/kg/min). The Bruce treadmill test is an indirect test. It estimates VO2 max using a formula and an athlete's performance on a treadmill as the workload is increased.

Other methods of measuring VO2 max are more cumbersome and require the direct collection and measurement of the oxygen volume and oxygen concentration of inhaled and exhaled air the athlete uses while running. Direct testing requires far more elaborate and sophisticated equipment and data collection than the formula based on time on the treadmill.

How the Bruce Treadmill Test Works

The Bruce protocol is a maximal exercise test where the athlete works to complete exhaustion as the treadmill speed and incline is increased every three minutes. The length of time on the treadmill is the test score and can be used to estimate the VO2 max value. During the test, heart rate, blood pressure, and ratings of perceived exertion are often also collected.

Bruce Treadmill Test Stages

Stage 1: 1.7 mph at 10 percent grade
Stage 2: 2.5 mph at 12 percent grade
Stage 3: 3.4 mph at 14 percent grade
Stage 4: 4.2 mph at 16 percent grade
Stage 5: 5.0 mph at 18 percent grade
Stage 6: 5.5 mph at 20 percent grade
Stage 7: 6.0 mph at 22 percent grade

Bruce Protocol Formula for Estimating VO2 Max

These are the formulas used. T stands for total time on the treadmill, measured as a fraction of a minute (a test time of 9 minutes 30 seconds would be written as T=9.5).

• For men: VO2 max = 14.8 - (1.379 x T) + (0.451 x T²) - (0.012 x T³)
• For women: VO2 max = 4.38 x T - 3.9

Bruce Protocol Norms

Bruce Treadmill Test Cautions 

Because the Bruce treadmill test is a maximal exercise tolerance test, it requires a physician's clearance and expert supervision. In an untrained individual or an athlete with an underlying heart condition, exercising to a maximal effort can lead to injury or heart events.

While performing the test, clinicians monitor the patient's vital signs continuously and stop the test at any sign of trouble. If you take this test, be sure that your testing facilitator has the appropriate clinical expertise and has conducted such tests many times before you step on the treadmill.