If you were alive in the '50s, you might remember those machines where you flung a big strap around your butt, flipped a switch and jiggled away all your self-esteem. Guess what? Those old-fashioned vibrating belts are back. But this time, they've sexified the name, padded their campaign with a few celebrities and started charging a heck of a lot more for the privilege of shaking your moneymaker.

But you know what? They actually work.

Aiming to tone, firm and beautify your body, the so-called PowerPlate workouts are knocking kickboxing out of the ring and dancing circles around Zumba. Tired, old routines just don't measure up. (Seriously, have you ever seen Heidi Klum at Curves?)

Celebs like Madonna, Claudia Schiffer, Natalie Imbruglia, Donatella Versace, George Clooney and even Clint Eastwood have all given the PowerPlate workout their star-studded seal of approval.

But do they work for regular people? You know, the moderately chunky, 20-to-30-somethings like you and me who would rather be waterboarded than do another spin class?

You're about to find out.

I decided to live like Madonna and try out the PowerPlate workout for a month to see if it did anything for me.

Luckily, I live in Los Angeles, so I didn't have to look far to find a gym that suited my needs. I use the term "gym" loosely, because what I found is actually a hybrid spa-gym, called FBE Spa (or Firm Body Evolution Spa), complete with body composition analyzers, whole-body-vibration machines, the miraculous jade infrared pods (don't worry, I'll get to those), pneumatic compression machines, back massage beds, hip rotators and unlimited access to ionized alkaline water.

The FBE spa was just a hop-skip from my house, so I couldn't wait to get my jiggle on. I met with Joseph, the owner, and he walked me through the process, explaining the benefits of this type of holistic workout regime.

Whole-body-vibration training, according to the spa's website, goes well beyond toning and firming muscle. It also has been shown to:

• improve bone density
• accelerate weight loss
• reduce cellulite
• improve blood circulation
• decrease physical and emotional stress
• improve balance, equilibrium and dexterity

They had me at "reduces cellulite." The first step was to get my fat analyzed to find out how much I needed to lose and where. Always a thrilling task. I found out that I'm flabby on paper, too.

Then I got a free personal training session. (It comes with every gym membership purchase; I wasn't special.) I stepped on the PowerPlate, my trainer set it to level 15 -- they go up to level 40, which I was told only Olympic athletes can handle -- and I was off. The PowerPlate literally rocked my world. My whole body vibrated, shook and jiggled. If I bent my knees, I felt it in my lower half. If I straightened them, it was shaking my brain.

I was told that just standing on the PowerPlate for 10 minutes is akin to a 60-minute workout. But I was determined to do more, so my awesome trainer put me through a rigorous 30-minute routine where I squatted, lunged, plié'd, push-upped and planked my way into a major sweat.

This is why Madonna's arms are so amazing. It was one tough workout!

Afterwards, I was sent into a blissful room with low lights, soft music and eight white pods all in a row -- the jade infrared sauna room I mentioned earlier. Also included in the membership, these little pods might well be the best part about joining the gym. For 30 heavenly minutes, I cozied up in one of those bad boys and sweated my butt off. (You can burn up to 600 calories.)

According to the spa's website, infrared saunas can also:

• burn calories
• improve skin by cleansing the pores
• detoxify the body
• strengthen the immune system
• increase cardiovascular conditioning
• improve lymphatic circulation
• relieve pain

And they can help treat sciatica, menopause, arthritis, shoulder stiffness, rheumatism, acne, gastroenteric problems and insomnia, the spa says.

Side note: I yanked my back playing dodgeball one night and hit the infrared the next day. Totally cured. No joke.

After 30 days, I'm lighter, leaner and am pretty sure I have a hot Latin boyfriend and a few Grammys. (Kidding about that last part.) But while I'm not Madonna by a long stretch, I worked out like her for a month and feel much closer to the Material Girl than I ever did before. I've lost about five pounds, toned my arms, and feel tighter and fitter all around.

My conclusion on the PowerPlate workout is this: It's fun, it's easy, and it's up to you to decide how hard you want to make it. Some days I just stood on it and clenched my butt. Other days I pushed myself to the limit. The complete workout takes an hour (30 minutes on PowerPlate, 30 minutes in the sauna), and the best part is that I wasn't stuck doing it at some clanky meat-market gym. Serenity awaited me every time I walked through FBE's doors.

So, if you want to exercise like Madonna (and me), give the PowerPlate a try. And if you happen to live in L.A., you could always do it at FBE. Just ask for Joseph. Tell him Sarah sent you.