They sound like one of those “But what could possibly go wrong?” contraptions that were George Jetson's nemeses. Whole-body vibration (WBV) – also known as “power plate” – exercise machines which shake users rather than provide resistance are becoming more popular, in both homes and gyms.

The machines are premised upon the idea that their vibratory energy, transmitted through your body, will force your muscles to truncate and relax dozens of times each second. The resultant “stress/relax” contractions will have a wide range of beneficial effects, which include weight loss, fat burning, improved flexibility, enhanced blood flow and increased strength. The health benefits are also said to include enhanced metabolism, increased bone mineral density, reduction of the stress hormone cortisol, elevation of human growth hormone levels, improved lymphatic flow, and reduced cellulite.

The vibration machine craze began in Russia, an outgrowth of the program used there to train cosmonauts. It's been a sensation in Europe, and then Japan, before making it's way to the U.S. Now there are entire gyms, like Platefit in Los Angeles, devoted only to shaking your booty.

WBV machines cost considerably less than treadmills, but do they work? They do on mice, at least. One study reported that a rodent who spent 20 minutes a day on vibrating platform over the course of three months reduced fat in its abdomen and liver and increased levels of the bone-strengthening protein, osteocalcin.

Studies on humans have been rare at this point, but one which focused upon 90 postmenopausal women was done in Belgium. The scientists saw an almost 1 percent increase in hip bone density among WBV users, along with measurable increase in muscle strength. The test subjects used the machine for a total of 30 minutes three times a week for six months.

Another study reported that elderly people who were not able to participate in traditional exercise might benefit from WBV machines. The data indicate that the participants saw muscle strengthening and speed-of-movement benefits from using the Power Plate. Key takeaways from the report include:

• 2 days and 4 days per week of WBV training during 8 weeks showed the same improvements on muscle strength.
• 3 weeks of detraining did not reverse the gains in strength made during 32 sessions of WBV exercise.
• 3 weeks of detraining did reverse the gains in strength made during 16 sessions of WBV exercise.

If you intend to adopt a regimen of WBV training – and especially if you are elderly – check with your physician first. It can be harmful in some situations.

There is one caveat of which aspiring low-budget WBV fans should be aware. Not all vibration is alike, so merely sitting atop your washing machine during the spin cycle is not going to give you six pack abs.