When you exercise, your heart speeds up to meet your body's energy needs. If you know your target heart rate, you can make sure you're exercising hard enough to get a good workout, but not too hard to strain your heart.

Your target heart rate is a range, expressed as percentages of your maximum heart rate. (Your maximum heart rate in beats per minutes is based on how old you are -- it's 220 minus your age.) For most people, the American College of Sports Medicine recommends a target heart rate while exercising of 50% to 85% of your maximum heart rate.

Why a range and not a single number? It depends on your fitness level. If you haven't exercised in a while or recently started, aim for a heart rate on the low end of your target heart rate, 50% to 65% of your maximum. If you're a regular exerciser, you should be in the middle of your range, 60% to 75% of your max. Very active people can pump it up to 70% to 85%, on the high end of the range.

To stay in the zone, check your heart rate regularly while you exercise. You can feel your heartbeats in several ways:

Place your fingers lightly but firmly over the inside of your wrist.
Place your fingers lightly on your neck, just below the angle of your jaw.
Place your palm on your chest over your heart.
Then count the number of beats that you feel while the seconds go by on a clock or watch. You can change the number of seconds above to see what your target heart rate range is for different time spans.

If you check your pulse at your neck, be careful not to use too much pressure because that can slow your heart down. That could be dangerous, especially for people who have blockages in the blood vessels in their necks.

Talk to your doctor if you have any questions or concerns about exercising or your target heart rate.

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http://www.webmd.com/fitness-exercise/healthtool-target-heart-rate-calculator
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