HEARTBEATS

Did you ever notice that your heart beats faster when you are playing soccer or doing other sports? Why does that happen? Well, the normal human heart beats 60 to 100 times every minute. When you exercise, the heart beats much faster—up to 200 beats per minute. Your muscles need more oxygen, so the blood carries oxygen to the muscles. The muscles create more waste (like carbon dioxide and acid) during exercise, so the blood carries it away.

Other things cause the heart to beat faster too. Emotions like fear and anxiety make the pulse increase. Think about your reaction to a big dog barking at you. Your heart beats much faster so your body is ready to run away (but you should never run away from a dog, or it will chase you). Some medicines can make it happen, too. If you take medications for a cold, the flu, or asthma, your heartbeat can increase. Other factors can affect your pulse. If you are worried, tell your mom and dad to