You're chugging up hills. You're blasting through mountains. You're skimming through waterfalls.

You change speeds just as you and your comrades prepare to take on the next mission at hand. You're ready to take America by storm.

And just think, it all takes place in the comfort of your aerobics room.

Spinning is just the newest fad for fitness fanatics, a bizarre blend of cardiovascular activity and wild imagination geared at packing the fun into your everyday workout.

Just one glance into the aerobics room during a spinning class will convince you of its electrifying appeal.

They're all set up in neat, little circle - a row of specialized stationary cycles - as the participants of this class whirl through the session like the cast of "American Flyers".

Originating in Los Angeles in the early '90's, spinning has since been a growing beneficiary from the fitness boom, racing through fitness clubs throughout the United States. Spinning has caught fire particularly in East Coast cities like New York and Boston, while a number of spinning studios are also being built in southern Florida. There are currently over 4,000 gyms throughout the world featuring spinning classes, nearly half of them inside the U.S.

Much of the appeal of a particular spinning classes lies with the effectiveness of the instructor. A fun, highly motivating instructor with a colorful imagination can provide the participants with the most riveting of sessions.

Another perk to spinning, particularly for newcomers, is that it is not a difficult activity to jump into. Unlike the step classes, you do not need to learn any specialized moves for this class. You just plop down on a cycle and start chugging away.

Also, because the activity is virtually stress-free on your joints, it is appealing to athletes and trainers who are injury-prone.

Meanwhile, spinning can give you a great full-body workout, especially throughout the muscles in your legs and buttocks.

But keep in mind, spinning classes are not for everyone. While spinning is generally regarded as a low-impact form of cardiovascular activity, it can also be quite rigorous, especially for newcomers who are not accustomed to such a workout.

However, because spinning does not require tremendous athletic coordination, it is starting to catch on with a wider variety of workout fanatics.

But unlike many aerobics classes, spinning does require a small fee to participate.