Seems that if you wait around long enough, what's old is new again.

You see it in fashion — flared jeans made a bit of a comeback a few years ago, for instance.

You see it in the news business. Dollar woes: a high dollar's going to kill our economy. Dollar woes: a low dollar's going to kill our economy.

Folks, it happens in the get-fit-quick exercise biz, too. Seems that shaking yourself into fitness is back in style.

Maybe you've seen images of fitness clubs back in the 1960s or scenes from 1950s black-and-white movies — people facing a row of machines, vibrating belts wrapped around their hips. Designed to tone your waist, firm your abs and help get rid of unwanted weight.

All it did was jiggled your fat. I remember being hooked up to one of those things at a gym in Montreal when I was still in my teens and convinced that I was far more overweight than I was.

Now, some companies are aggressively promoting machines that vibrate up to 50 times a second in three directions that will help tone muscle and let you get more out of your workout. There are pricey models designed for the gym and cheaper ones that you can use at home.

NASA's studied the concept. It's keenly interested in ways to prevent muscle atrophy and loss of bone density for astronauts who spend long periods of time in space.

But some researchers are concerned about the long-term effects of exposing yourself to high levels of vibration. At least one is worried that brain damage is possible.

The U.S. Food and Drug Administration has approved one device that's marketed as an abdominal toning belt. Slendertone guarantees you'll get "strong, firmer abs in just weeks."

The device is sold as an electrical muscle stimulator. It works like those muscle stimulators a physiotherapist would use to treat you for muscle strains.

The FDA says, "while an EMS device may be able to temporarily strengthen, tone or firm a muscle, no EMS devices have been cleared at this time for weight loss, girth reduction, or for obtaining 'rock hard' abs."

The FDA further notes that based on currently available data, you won't create a major change in your appearance unless you watch your diet and add regular exercise to your routine.

And that's the bottom line. There's no shortcut to fitness.

There's no pill or machine that's going to turn a mushy midsection into abs of steel.