Heart rate.

Heart rate is the beats you heart makes. Doctors can use it to find out the health of a patient. The normal heart rate for a 13-14 year old girl rests 70-80, one may have a higher dose not mean they may be healthy then the other. (I worked this out by going on to this website and kids uploaded there heart rates then I got the average) When you exercise your heart rate increases reason being is that you start to breath really fast and your blood gets pumping and then your heart beats faster. As you get older your heart rate decreases because your body isn't strong enough. You can measure your heart rate with doctor equipment such as medical machines and just as simple as putting your two fingers up to your neck in a special spot.