Hold out your hand and make a fist. If you're a kid, your heart is about the same size as your fist, and if you're an adult, it's about the same size as two fists. Your heart beats about 100,000 ...

Cardiac output close cardiac outputThe amount of blood pumped by the heart in one minute. Heart Rate x Stroke Volume = Cardiac Output. is the total volume of blood pumped out by the left ventricle ...

is the number of times the heart beats in one minute. The average number of beats is 72 beats per minute. Stroke volume (SV) is the volume of blood pumped out of the heart with every beat.

Originally appeared on the NOVA Web site Cut ... beat more than 2.5 billion times. Give a tennis ball a good, hard squeeze. You're using about the same amount of force your heart uses to pump ...