The study was conducted on a total of 30 male volunteers in the age range of 16 to 22 years. The subjects were grouped in to Aerobic, Anaerobic and Sedentary groups based on their training specialty. The aerobic group consisted of 8 trained cyclists while the anaerobic group consisted of 3 sprinters, 4 footballers and 5 wrestlers. Both the aerobic and anaerobic groups were trained for a year and above. The sedentary groups comprised of 10 students from different departments of Punjabi University, Patiala and were not taking part in any regular exercise program. The main aim of the study was to compare the ECG responses to graded treadmill exercise among the aerobic, anaerobic and sedentary groups as well as to report the effect of intensity of exercise on the ECG. All the subjects of the study were administered a graded treadmill test using Modified Bruce Protocol that consisted of nine stages each of which lasted for 3 minutes. All the subjects completed all the nine stages. Exercise test was performed on Electrical Treadmill.