The Bruce Test is commonly used treadmill exercise stress test. It was developed as a clinical test to evaluate patients with suspected coronary heart disease, though it can also be used to estimate cardiovascular fitness. See also a general description of Exercise Stress Tests. As this stress test is a maximal test performed commonly on people with heart problems, the test should be performed under the supervision of appropriately trained medical staff.
Aim: To evaluate cardiac function and fitness.
Equipment Required: Treadmill, stopwatch, a 12-lead electrocardiograph (ECG) machine and leads, sticking tape, clips.
Procedure: Exercise is performed on a treadmill. If required, the leads of the ECG are placed on the chest wall. The treadmill is started at 2.74 km/hr (1.7 mph) and at a gradient (or incline) of 10%. At three minute intervals the incline of the treadmill increases by 2%, and the speed increases as shown in the table below. The test should be stopped when the subject cannot continue due to fatigue or pain, or due to many other medical indications.
| Stage | Speed (km/hr) | Speed (mph) | Gradient |
|---|---|---|---|
| 1 | 2.74 | 1.7 | 10 |
| 2 | 4.02 | 2.5 | 12 |
| 3 | 5.47 | 3.4 | 14 |
| 4 | 6.76 | 4.2 | 16 |
| 5 | 8.05 | 5.0 | 18 |
| 6 | 8.85 | 5.5 | 20 |
| 7 | 9.65 | 6.0 | 22 |
| 8 | 10.46 | 6.5 | 24 |
| 9 | 11.26 | 7.0 | 26 |
| 10 | 12.07 | 7.5 | 28 |
Modifications: There is a commonly used Modified Bruce protocol, which starts at a lower workload than the standard test, and is typically used for elderly or sedentary patients. The fist two stages of the Modified Bruce Test are performed at a 1.7 mph and 0% grade and 1.7 mph and 5% grade, and the third stage corresponds to the first stage of the Standard Bruce Test protocol as listed above.
Results: The test score is the time taken on the test, in minutes. This can also be converted to an estimated VO2max score using the calculator below and the following formulas, where the value "T" is the total time completed (expressed in minutes and fractions of a minute e.g. 9 minutes 15 seconds = 9.25 minutes). As with many exercise test equations, there have been many regression equations developed that may give varying results. If possible, use the one derived from a similar population and which best suits your needs.
VO2max (ml/kg/min) = 14.76 - (1.379 × T) + (0.451 × T²) - (0.012 × T³)
Women: VO2max (ml/kg/min) = 2.94 x T + 3.74
Women: VO2max (ml/kg/min) = 4.38 × T - 3.9
Men: VO2max (ml/kg/min) = 2.94 x T + 7.65
Young Men: VO2max (ml/kg/min) = 3.62 x T + 3.91
Target Population: Patients with suspected coronary heart disease, and athletes in sports in which aerobic endurance is a important component, such as distance runners.
Advantages: You can also get measurement of maximum heart rate by recording heart rate during the test, which can be used in training programs to set intensity.
Disadvantages: Relatively large time and costs required. Specialist training is required to interpret exercise ECG traces.
Other Comments: The original Bruce protocol was developed in 1963 by Dr. Robert. A. Bruce. Other similar exercise stress test protocols include Astrand, Naughton and Balke.
Caution: This test is a maximal test, which requires a reasonable level of fitness. If used recreational athletes or people with health problems, injuries or low fitness levels, please have medical assistance on hand.