A doctor normally conducts a treadmill stress test in three stages that each last three minutes, according to WebMD. After each stage, there is an increase in speed and steepness, so the patient must walk faster and at a steeper incline.
A patient's electrocardiogram and heart rate are recorded continuously during the test, while a doctor measures blood pressure during the second stage, explains WebMD. More frequent readings may occur if the blood pressure is too high or low. A doctor may ask how difficult the exercise is on a scale from six to 20, known as the rating of perceived exertion. The test ends when the patient needs to stop, reaches his maximum heart rate or begins to show symptoms of stress on the body.