Run hard, don’t just jog. “Exercise increases your heart’s efficiency, reducing the number of heartbeats you need to achieve bloodflow,” says John Elefteriades, M.D., the chief of cardiothoracic surgery at Yale University.
Interval training can increase your heart’s stroke volume (the amount of blood it pumps with each heartbeat) by about 10 percent, but slower, sustained running has no effect on it, according to an American College of Sports Medicine study.
Try a 4-minute run at 90 percent of your maximum heart rate, and then jog for 3 minutes at 70 percent. Repeat the interval three times. Do this routine three times a week, as the study participants did.