Your heart rate is your body’s speedometer. When you’re playing or working hard your heart rate is high; when you are at rest your heart rate is lower. Resting heart rate can be used to monitor changes in cardiovascular fitness. Specifically, a decrease in your resting heart rate after you have done regular aerobic exercise for a few weeks is an indication of improved cardiovascular fitness.
How does this happen? The answer is simple: Aerobic exercise strengthens the heart muscle. A stronger heart muscle is able to pump more oxygenated blood to the body with each beat. A stronger heart can beat fewer times per minute than a weaker heart to supply the same amount of oxygen to the body.
