You peek into the aerobics room on your way out the door and see that they're kicking up a storm in there. At first, they look like either an array of Rockettes or a Broadway dance audition. Knees are pumping, legs are snapping, and feet are flying everywhere.

And let's not forget the sweat. It's pouring down by the bucket.

Sure, to the curious on-watcher, it would be difficult not to be swept up into the most publicized cardio craze to capture the nation in nearly two decades. Not only can cardio kickboxing pack a knockout punch for your fitness goals, but judging by the expressions on the faces of its participants, the activity is also a knee-slapping good time.

Millions across the country are getting a kick out of cardio kickboxing, whether it's in the form of the insanely popular Tae-Bo or some of the more general forms offered by local martial artists, fitness trainers, and boxing fanatics.

Not since Jane Fonda helped trigger the aerobics explosion in the 1980's has any form of cardiovascular fitness captivated the country so convincingly. It seems like cardio kickboxing classes are cropping up in every aerobics room, in every gym, in every city across America. The man behind most of this is Billy Blanks, the seven-time Martial Arts champion and the quick-kicking dynamo you'll see on the countless Tae-Bo infomercials.

A handful of Hollywood celebrities are swearing by it - guys like Sinbad, Shaqille O'Neal, and Magic Johnson. Gals like Pamela Anderson, Goldie Hawn, and Carmen Electra are saying much of the same.

But next time you're on your way out the gym door, stop and take a closer look in the aerobics room. You may even recognize a few faces.

After all, you don't need to be Van Damme to do it. You can simply be the guy next door.

Cardio kickboxing, like aerobics classes, is usually offered in three different forms of intensity: low-impact, moderate-impact, and high-impact. While the low-impact version is an excellent way to obtain flexibility and form, the intensity of the high-impact class is a tremendous method of losing weight and strengthening the heart.

After a few weeks of taking the classes, you're likely to build endurance, while improving your speed, power, and agility.

But the appeal in cardio kickboxing lies elsewhere. While benefiting from a fantastic sweat session, participants also learn the various punches and kicks that have derived from different Martial Arts forms. In other words, as much of a fitness class that it is, it is also a self-defense class.

Don't walk into a cardio kickboxing class and expect to emerge as Bruce Lee. This is merely a class engineered to combine self-defense techniques with cardiovascular workouts and add a much-needed "kick" to your everyday workouts.

The most common testimony from participants generally revolves around two ideas. One is that cardio kickboxing is ideal in toning up the muscles, partiuclarly in the arms and legs, while getting you into top shape. And secondly, the kickboxing sessions, which many claim are indeed highly addictive, break up the monotony of those repetitive aerobics classes.

Above all, cardio kickboxing classes provide you in a shorter time with what hours of chugging along on the Stairmaster or stationary bike will. The full body workout - the punches, the kicks, the non-stop pivoting and moving - shoot by like a Jackie Chan movie. And you'll be equally exhausted when it's over.