In medical terminology a stress test is a test conducted to understand the functioning of the heart and the respiratory system. The human body has an ability to moderate its production of energy depending on the requirement of the time. Therefore, when a person is resting or doing little physical work, the body is producing and using very little energy. When the body’s rate of physical activity picks up, the process of metabolism speeds up to produce more energy. This process causes the heart rate and the rate of respiration to increase. These increases occur so that the extra oxygen and nutrition required by the muscles of the body is provided to the muscles that are working hard at that moment. During this period of load, the body behaves differently because the heart is pumping much harder and the lungs are exchanging much more air. Any problem with these organs is likely to be more visible under stress than when those organs are relaxed. Many mechanical devices that we use tend to display the same characteristics of being normal at idle but abnormal under load.
A stress test involves measuring the subject’s pulse, blood pressure and other cardiac related measurements. The concerned person is usually tested when they are idle and then gradually made to exercise using a treadmill. The physical strain of the treadmill is constantly increased by increasing the speed and slope of walking. This gradual and continuous increase in effort may show some abnormalities. However, sometimes this does not show any abnormality even when a problem exists. In this case, the test might start slowly and then suddenly be increased to full effort. Some people struggle with a sudden increase in stress and it is this situation that brings out the worst of their problems.
Stress test abnormalities are the ones that are diagnostically relevant and that a doctor is looking for, especially if other related symptoms are noted. An example of a stress test abnormality that crops up during testing is that of a heart valve problem. When the heart is under low or moderate pressure, the valve is able to hold blood within it when it closes and this is its normal function, exactly what it is designed to do. However, when the blood pressure increases, the valve may leak blood which causes the heart to have an abnormal flow pattern of blood. This sort of abnormality is what a stress test is designed to capture.