The most common heart disease is caused by narrowing of the coronary arteries. Mild narrowing usually causes no symptoms. Most people with narrowing of the coronary arteries have no symptoms at rest. The exercise test helps to identify those people with significant narrowing in their arteries.
Exercise increases the work of the heart.
More work requires more blood for the heart muscle. Narrowing of the coronary arteries reduces the amount of blood that can flow through the vessels. The lack of enough blood to the heart muscle causes specific changes in the electrocardiogram. Recording the electrocardiogram before, during, and after exercise shows these changes. The motorized treadmill and the stationary bicycle have become the preferred form of test exercise.