FIGURE 2.

Change in pulmonary ventilation during constant high-intensity exercise (dashed red line) and interval training at the same work rate (red solid line) as a function of time of exercise. With constant exercise at high intensity, patients often reach maximum voluntary ventilation and have to stop the exercise. With shorter bouts of exercise, the pulmonary ventilation remains further from the maximum pulmonary ventilation and hence patients experience fewer symptoms during exercise.