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Every time people find out what I do for a living, they immediately launch into their most pressing questions about nutrition and fitness. Recently, a woman approached me in the supermarket and started asking me about heart rate monitors. 

She wasn't a professional athlete -- in fact, she was out of shape. She had heard that by using a heart rate monitor she could determine her optimal "fat burning zone" and save herself time while exercising. My first question for her was, "Well, what type of exercise do you do?" Her response was typical -- NONE. She hadn't even started with any exercise program, and yet she was already worried about a heart rate monitor.

WHAT IS A HEART RATE MONITOR?
What are these devices made by Nike, Polar, Reebok and Suunto that you see so prominently displayed in sports stores? Most consist of a watch worn on your wrist and a wireless plastic transmitter that's strapped against the bare skin of your chest. The transmitter picks up electronic signals from your heart and sends them to the watch, providing a continuous display of your heart rate.

There are also heart monitors that don't need an uncomfortable chest strap (made by Mio and Reebok). They are just as accurate, and require that you place two fingers on the watch and wait a few seconds for the watch to calculate your heart rate. Unfortunately, these monitors don't provide continuous readings of your heart rate -- you have to place your finger on the device each and every time you want a reading. Additionally, many pieces of exercise equipment these days come with built-in heart rate monitors.

OLYMPIC ATHLETES ONLY?
The primary purpose of a heart rate monitor is to have a better understanding of your exercise intensity. "This is specifically important if you are a high-performance, competitive athlete. Knowing your heart rate and exercise intensity can help to determine where your anaerobic threshold exists (the point at which your muscles start to get tired). From that point, with proper coaching and training, you can gradually increase that threshold and sustain peak performance for longer periods of time," says Walter R. Thompson, Ph.D., FACSM, professor of exercise science at Georgia State University.

And what if you're an occasional exerciser or just starting an exercise program? Are heart rate monitors a total waste of money? Not entirely -- they can still provide benefits even to those of us who aren't training for the next Olympic Games. 

"Many times, beginner participants may not be aware of what it means to exercise at a moderate intensity or at a certain percentage of their maximum heart rate, which in turn will affect their workout," says Carla B. Sottovia, Ph.D. of The Cooper Fitness Center, Dallas, Texas.

In fact, if you exercise too hard, you will most likely quit before you get real benefits (and it could be dangerous). We have all seen people who start out jogging or biking too fast and stop after just a few minutes because they're pooped. But if you know when to stop pushing it, you can exercise for longer periods of time, get in better shape, and achieve greater exercise benefits. And a heart rate monitor can help you do that, by letting you know when you're within your "target" heart rate. 

Others still feel that heart rate monitors are overrated. "I've been exercising for over 40 years, and I'm having just as much fun, my exercise is just as effective, and I'm getting the same health benefits I was getting before the existence of heart rate monitors -- it's just not a requisite part of a fitness regime," says Mitchell Whaley, Ph.D., chairman of the School of Physical Education at Ball State University in Muncie, Indiana.  

And although studies have shown that people who use monitors tend to stay with an exercise program longer, any kind of self-monitoring helps you stick to your chosen regimen. "You could simply take a calendar, mark the days you exercise with a big 'X' and increase your adherence -- a heart rate monitor is an upscale way of monitoring what you've done," says Carl Foster, Ph.D., FACSM, professor of exercise and sports science at University of Wisconsin-LaCrosse and spokesperson for the American College of Sports Medicine.

TARGET HEART RATE
Your target heart rate zone represents the minimum and maximum number of times your heart should beat in one minute of exercise. To find your target heart rate, you first need to know your maximum heart rate -- your upper limit for exertion. It's recommended that you exercise within 60 percent (even lower for beginners) to 85 percent of your maximum heart rate.

How do you determine your maximum heart rate? For years, the rule of thumb has been to subtract your age in years from the number 220. The problem is that this formula is, at best, an "educated guess."

"Many people use this age formula, but it may or may not be accurate. Often times using this 'age' based method can defeat the purpose of actually using the heart rate monitor to determine exercise intensity," cautions Whaley. "This creates the illusion that you are exercising with a sophisticated device, but the reality is that your heart rate can be plus or minus 20 beats from what the formula predicts to be your maximum heart rate. That's quite a bit."

This can result in the non-exercisers exercising too hard (which can be hazardous) or fit people not exercising hard enough. Most experts recommend getting a stress test at an exercise lab or your physician's office to determine your maximum heart rate. This is particularly important for men over age 45 and women over age 55 because of the increased risk of cardiovascular disease.

But do you really need a heart rate monitor to determine if you are exercising too much? It can help, but you can also do the "talk test." "Try reciting something you know really well while exercising, such as the Pledge of Allegiance. If you can speak comfortably and say it clearly, without any problems, you're doing just fine and are probably in the 50 to 80 percent range. If you waffle a bit, you are probably working at 80 to 90 percent of your maximum heart rate. If you can't talk at all, you're above 90," says Foster.

Also, keep in mind that medications such as beta-blockers for high blood pressure and cardiovascular disease can affect your target heart rate. Always consult your healthcare provider before starting any exercise program.

THE NEXT DIET TREND?
Does keeping your heart working at a certain rate burn more fat? Not really. "The fat burning zone just doesn't exist," explains Thompson. Yes, there is a heart rate zone in which the fuel mixture is more fat than carbohydrate, but it's not necessarily the stored fat that is in your thighs or stomach that's being burned. "Aside from the fuel mixture -- which is mostly irrelevant if you're trying to look leaner -- the most important point in terms of weight loss is the duration of the exercise. If you can exercise for longer periods without getting tired too rapidly, then you will have more of an energy deficit, meaning you will burn more calories, and burning calories is what matters for weight loss," adds Thompson.

BOTTOM LINE
Do you really need a heart rate monitor? If you're a competitive athlete or if it just helps you stick to an exercise program -- it's great. Nevertheless, as Dr. Thompson reminds us, "It's more important for someone to just go out there and take a walk, than to worry about being in the target heart 'zone.'"

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