Pregnancy, menopause, and thyroid issues can all create a lot of changes in the body because your hormones are out of whack. Possibly your heart skips a beat here and there as an increase in blood ...

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 ...

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 ...