Last year, the American Heart Association joined the American College of Sports Medicine to update guidelines on exercise frequency, duration and intensity to promote a fit and healthier heart. They now recommend a minimum of walking moderately for 30 minutes five days a week or striding at a more vigorous pace for 20 minutes three days a week. "Moderate walking is the safest and most manageable heart-strengthening exercise, but it's not enough to realize that. You must lace up your walking shoes and do something about it," says Dr. Nieca Goldberg, a cardiologist in New York City and the medical director of New York University's Women's Heart Program.

However, most people don't know if they're walking intensely enough to glean these benefits, and many can benefit from a heart rate (HR) monitor. The simplest way to determine if you're exercising hard enough, though, is completely free. It's called called The Talk Test. You should be able to comfortably carry on a short conversation without excessively panting during a walk. On the other hand, if you're able to carry on a full debate with your neighbor, then you you're not walking hard or fast enough, and you should bump up your walk. "I constantly remind patients that the appropriate speed, even for beginners, is considerably faster than a window shopping pace," says Goldberg, who is also the author of "The Women's Healthy Heart Program." If you're a marathoner or a triathlete, investing in a HR monitor also ensures that you can clock yourself at differing intensities, and shave minutes off race times.

Here's what I consider the general advantages of purchasing and using a heart rate monitor:

Pro: Wrist units and chest monitors deliver instant training feedback and are known to help more experienced competitors across multiple sports.
Con: They run anywhere from $55 to $500, depending on your activity and how many features you require (audible alarms, GPS, water resistant features, etc.). If you don't need a built-in stopwatch or a sophisticated tracking system, don't buy these features!
Pro: HR monitors help establish very basic fitness goals ("I want to walk a 12-minute mile") and aid beginners in discovering their own proper fat-burning target zones during aerobic exercise.
Con: Most active folks don't need the fancy bells and whistles in even mid-range heart rate monitors. Always do your homework with gadgets like this so they don't become expensive clutter in the back of your junk drawer.

To clock your own training intensity or practice The Talk Test, check out these fitness workouts from A to Z.