Cardiac output (volume of blood pumped per minute) is what you get when you multiply the stroke volume (the amount of blood pumped with each beat) by the heart rate (number of beats per minute). Since heart rates at maximum exercise levels decline with age, you might expect that cardiac output during vigorous exercise would also fall. Not so. Research now shows that, contrary to previous expectations, one’s so-called end-diastolic filling volume increases as one ages. This means that during vigorous exercise the heart fills with more blood between beats, making more blood available to be pumped with the next beat. Again, this is a kind of compensatory gesture that the body seems to make to keep things running smoothly over time.
