Physical exercise—be it for therapeutic reasons, or sport, or simply for the fun of it—is also an exercise in diagnosis. By observing the limits of their exercise tolerance, exercisers monitor their endurance and diagnose their fitness or its shortcomings.
Exercise became a diagnostic tool formally when physicians began to measure its effect on the pulse rate and blood pressure. As a rough guide to cardiac performance, these measurements proved clinically useful. More refined measurements of the effect of exercise on oxygen consumption and on other biochemical and hemodynamic parameters have further enhanced its value in diagnosis.
With the advent of electrocardiography, exercise rose to even greater prominence. The Master two-step exercise test gave it an almost decisive voice in the diagnosis of ischemic heart disease. When the test proved wanting in specificity and sensitivity, the treadmill and bicycle ergometer largely replaced it. These sophisticated modifications, however, also appear to be