Pulse is the regular expansion of the arteries caused by the surge of blood that occurs each time the heart beats (contracts). It can be felt by gently pressing the fingers on certain blood vessels that are close to the skin's surface.

Pulse is also called heart rate, which is the number of times the heart beats per minute (bpm). The wrist and neck are common places to take a pulse.

Doctors usually check a person's pulse at checkups or in an emergency. A weak pulse or a change in pulse rate or rhythm may be a sign of heart disease or other problem.

One way to know how hard you are exercising is to use your target heart rate. Your target heart rate is a percentage of your maximum heart rate. One way to find your maximum heart rate is to subtract your age from 220. After you know your maximum heart rate, you can find your target heart rate for moderate and vigorous aerobic activity.

• Moderate aerobic activity is 60% to 70% of your maximum heart rate.
• Vigorous aerobic activity is 70% to 80% of your maximum heart rate.

Target heart rate is only a guide. When you exercise, pay attention to how you feel, how hard you breathe, how fast your heart beats, and how much you feel the exertion in your muscles.

Chronic health problems and certain heart medicines affect a person's target heart rate range.