The aim of the study was to compare (1) the intensity of leg effort and dyspnea during exercise and (2) subjective limitations to performance in normal subjects, patients receiving medication for cardiac disorders, patients with pulmonary impairment, patients with pulmonary impairment who were also receiving cardiac medications, patients experiencing chest pain during exercise, and patients who had a reduced exercise capacity but did not have pulmonary impairment and were not receiving cardiac medication. Five hundred seventy-eight subjects rated the intensity of leg effort, discomfort with breathing (dyspnea), and chest pain every minute (Borg scale) during an incremental exercise task (100 kpm/min each minute) to maximum work capacity on a cycle ergometer and following exercise indicated their subjective limitation by completing a simple questionnaire. Leg effort and dyspnea increased systematically with power output in a positively accelerating manner in all groups; both symptoms were significantly more intense in the impaired groups compared with the normal group at submaximal power outputs. In all groups, there was a significant relationship between symptom intensity at submaximal power outputs and the maximal power output achieved. Leg discomfort in combination with breathing discomfort was the predominant subjective limitation in all groups; chest pain in combination with leg and breathing discomfort was the major subjective limitation in individuals with angina. Activation of the sensory systems during exercise is accompanied by a perception of discomfort associated with the peripheral exercising muscles and discomfort with breathing; both discomfort associated with the exercising muscles and discomfort associated with breathing contribute to exercise limitation to a large degree in normal subjects and patients with cardiorespiratory diseases.