Give a tennis ball a good, hard squeeze. You're using about the same amount of force your heart uses to pump blood out to the body. Even at rest, the muscles of the heart work hard—twice as hard ...

Do you prefer working out in the morning or the afternoon ... clock — a concept known as chronoactivity — might give your heart an extra boost, regardless of your chronotype.

Irregular heart rhythm -- arrhythmia -- is when your heart doesn't keep up a good beat. Learn what it means here. You may not know what a heart valve is -- until it stops working right.

Your heart first pumps blood to your lungs. Here, the blood picks up oxygen from the air that you have breathed in. The blood (carrying oxygen) then travels back to your heart. The heart gives the ...