Exercise seems easy enough. Throw on some running shoes or hop on a bike and off you go. However, to get the most out of a workout there's one more thing you need to know: your target heart rate.

Target Heart Rate: Setting Your Pace

While it may be tempting to take an easy stroll around the block and call it a day, exercising at the right intensity and for the right amount of time is key to improving health and reaching fitness goals. Your target heart rate, a specific number of beats per minute that you want to reach during exercise, is your guide.

"When you hear about target heart rate, we are really talking about a range to keep your heart rate in. This is used as an indicator of exercise intensity," says Laura Stusek, fitness coordinator for Westminster College in Salt Lake City. "There is no one target heart rate for everyone. It depends on your goals, age, and general fitness."

Target Heart Rate: Your Personal Range

Begin by subtracting your age from 220 to find your maximum heart rate, or beats per minute. Then multiply the maximum heart rate by .65 — this is the low end of your range — and by .85 — this is the high end of your range. The two numbers make up your target heart rate zone. Note that a person should never exercise at their full maximum heart rate.

As an example, a 30-year-old would subtract 30 from 220 and get 190 for the maximum heart rate. To find the low end of the target heart rate zone, multiply 190 by .65 for 124. For the high end, multiply 190 by .85 for 162. Therefore, the target heart rate zone for a 30-year-old is 124 to 162 beats per minute.

Target Heart Rate: Making Exercise Gains

"The target heart rate zone is where the greatest gains can be made without injury or overexertion,” says Thomas A. Fox, a workout advisor and author of The System for Health and Weight Loss.

Even within the target heart rate zone, variation is important. "Rather than just a single heart rate goal, it is beneficial to have multiple zones," says Erica Tuttolomondo, athletic director at Rush-Copley Healthplex, a fitness center Aurora, Ill. "Training in three different zones helps you exercise smarter, not harder. It can help you lose weight, increase metabolism, increase speed, and avoid overtraining."

A good workout, for example, would incorporate light (60 to 70 percent), moderate (70 to 80 percent) and hard (80 to 90 percent) zones.

Checking Your Target Heart Rate

Measuring your pulse can help you estimate where you are in your target zone. Put your index finger on the carotid artery at the side of the neck. Do not use the thumb, as it has its own pulse and can make counting inaccurate; be careful not to press too hard. Count for 10 seconds with the first beat as zero and then multiply by six.

"Pulse rate can only give an estimate of the heart rate during one period of exercise," says Tuttolomondo. For a truly accurate heart rate reading, consider purchasing a heart rate monitor. The best ones have a strap that goes around the chest and sends information wirelessly to a device worn on the wrist like a watch. Be wary of wrist-only monitors, as the area measured is small and it's difficult to get a truly accurate reading.

Also, watch out for exercise equipment that promises heart rate readings just by holding the handrails. Not only can these sensors pick up interference from cell phones, beepers, and music devices, but you also need to apply a consistent amount of pressure, and that can be hard to do while moving.

To increase your heart rate, "whatever activity you are doing, just go a little harder," says Stusek. "If you are in a kickboxing class, kick higher. If you are walking, try walking on an incline or jog a little." Some machines also allow for adding more tension, incline, or speed to boost the heart rate.

Target Heart Rate: The "Fat-Burning Zone"

The so-called "fat-burning zone" got its name because during low-intensity aerobic exercise the body uses fat as an energy source. At high intensities, on the other hand, the body works anaerobically, using stored energy like blood sugar for fuel. However, what’s most important is not the kind of energy used but the overall amount.

For example, interval training for 20 minutes, during which you alternate one minute of walking with one minute of jogging, burns more calories than simply walking for 20 minutes, even though the interval training moves you out of the fat-burning zone.

Your body will adapt to a set workout over time, so be sure to mix up your routine with different exercises, durations, and intensities to keep the body working hard. A little variety will help you keep your fitness goals and have fun in the process.