You're lying on the sofa, maybe munching a bag of chips, and watching your favorite movie on DVD. And ... you're toning your abs? That's the picture painted by some proponents of passive exercise, a fitness trend based on the idea that you can pretty much do nothing and still work out, if you have the right equipment doing the work for you.
But could this really work? WebMD asked three experts to offer up their opinions on four of the top passive exercise trends: whole-body vibration, chi machines, electronic ab stimulators, and inversion boots. So grab that bag of veggie chips, prop up your feet, and read on -- their answers might surprise you!
By far the most popular new addition to the passive exercise category is whole-body vibration or WBV -- also known as "Power Plate" exercise. An outgrowth of a program used to train Russian cosmonauts, it quickly spread through Europe and Japan, then hit U.S. shores -- with whole centers now devoted to this workout.
How It Works: According to physical therapist and personal trainer Ben Quist, DPT, most people stand on the platform with knees bent at about a 30-degree angle, while the surface beneath their feet vibrates an astounding 30 times per second.
That vibration, says Quist, tricks the body into thinking you're falling. "This, in turn, activates the 'stress reflex' -- an extremely rapid muscle contraction," says Quist, owner of Form and Fitness, a Milwaukee health club and rehabilitation center, where he has been training patients on the Power Plate for over a year. These muscle contractions, says Quist, are responsible for most of the benefits attributed to this type of exercise.
The Promise: According to manufacturers, those benefits include increased circulation, muscle strength, and flexibility; better range of motion; core conditioning and stability; and faster muscle recovery after working out. They say the health benefits also include enhanced metabolism, increased bone mineral density, reduction of the stress hormone cortisol, elevation of human growth hormone levels, and improved lymphatic flow. Whole-body vibration is also said to reduce cellulite and stimulate collagen production for smoother skin. Manufacturers also say MBV can provide muscle toning and conditioning for those who have health restrictions that keep them from exercising, such as multiple sclerosis, Parkinson's disease, and some forms of arthritis.
What the Experts Say: While the experts who spoke with WebMD all agreed that WBV does offer some benefits, all cautioned that the level is nowhere near the claims being made.
"I've seen some remarkable results in terms of bone density -- working better than conventional exercise -- plus good effects on circulation and muscle stimulation for those who can't do conventional exercise," says Quist. "But I don't think it can help you lose weight or impact cellulite. There is really no solid medical evidence backing up these or other health claims."
Cedric Bryant, PhD, chief science officer of the American Council on Exercise, says while whole body vibration has potential, more research is clearly needed.
"Right now, the marketing and hype is greatly outpacing the research and the scientific evidence -- but that said, from a conceptual standpoint, it could presumably improve muscle strength and stability, and an increase in bone density," says Bryant.
Indeed, in one study of 90 postmenopausal women published in the Journal of Bone and Mineral Research in 2004, a group of Belgian researchers found almost a 1% increase in hip bone density among users of the Power Plate form of WBV, along with measurable increase in muscle strength. The study participants used the machine for a total of 30 minutes three times a week for six months.
In another study, published in the Journal of the American Geriatric Society, researchers found that elderly people who were not able to participate in traditional exercise saw muscle strengthening and speed-of-movement benefits from using the Power Plate.
And in a study published in Proceedings of the National Academy of Sciences, mice that were placed on a low-vibration platform for 15 minutes, five days weekly, for 15 weeks ended up with smaller torsos than a group of mice who were put on a platform that didn't vibrate -- even though all the mice ate the same amount of food.
Still, Gerard Varlotta, DO, remains unconvinced that whole-body vibration can replace conventional exercise.
"We know that walking 2 miles a day is an effective way to build bone -- and I think it's OK to use this equipment as an adjunct to your normal exercise routines -- but to rely on it solely, we're not there yet," says Varlotta, director of physical therapy at the Rusk Rehabilitation Center at New York University Medical Center.
As with whole body vibration, these machines shake the body from the ankles up. The big difference is that the moving and shaking goes on while you're lying down.
How It Works: You lie on the floor (or a treatment table) and place your ankles on top of a small square box that basically vibrates your body from the feet up.
The Promise: The benefits are supposed to include improved metabolism, weight reduction, increased energy, muscle relaxation, increase in cell oxygenation, and stimulation of the sympathetic nervous system. Some proponents say that just five minutes on the Chi machine is the aerobic equivalent of walking for 30 minutes.
Chi machines are also advertised as being beneficial for those with diabetes, fibromyalgia, lymphodemia, and migraine headaches, as well as those who want to tone their muscles and lose weight -- all while lying down for just 15 minutes a day.
What the Experts Say: "This is a totally passive way of supplying increased circulation to a muscle and that's all," says Varlotta. "It will not give you increased strength, and it could never replace exercise done standing on your own two feet."
Quist likens it to the "jiggly belts" used in the 1950s, which simply caused your body to shake.
"I don't think they ever proved scientifically that those belts did anything for weight loss, and I think the effect is similar with the Chi machines," says Quist.
Bryant agrees:"Part of the thinking here centers on the Eastern philosophies of energy centers and those are being stimulated by this movement activity, but I have not seen anything even close to science on that," he says.
He adds that if you just lie on the floor and kick your legs, you would probably get a similar circulatory effect, along with some muscle toning.
Electronic Muscle Stimulators: Ab Stimulating Machines
It's hard to miss the ads for these products -- svelte, toned guys and gals in bikinis, showing off their "six pack" abs, ostensibly delivered courtesy of electronic ab stimulation.
How They Work: You strap on a wide belt wired to a battery. Stimulation is provided by tiny electrical "shocks" delivered at timed intervals, designed to stimulate muscle contractions.
The Promise: You'll not only have stronger, firmer, more visible abs in 30 days, but you can achieve this without ever getting off your couch, some manufacturers say. One company says you can tone all the muscles in your abdomen in a few weeks using the machine just 30 minutes a day -- while you "watch TV, fold laundry, or help your kids with their homework."
What the Experts Say: According to Bryant, the principal behind ab stimulators comes directly from physical therapy, where it's used to help contract injured muscles. However, he cautions that what works on a damaged muscle will have minimal effects, at best, on a healthy one.
"While you may see some mild improvement, the only way to see 'six pack abs' is to lose the belly fat -- and these stimulators will not help you to do that," says Bryant.
Quist adds that the amount of stimulation necessary to tone healthy muscles would be so great that you would likely burn or injure yourself in the process. "I see no real value for healthy muscles," says Quist.
Varlotta agrees. "If you go back to the basic principals of muscle stimulation, it's to help bring nutrients into the injured area and increase blood supply," he says. "But the studies have failed to show any increase in strength or endurance. So, from a healing standpoint, it may help if you have an injury, but that's about it."
Moreover, in 2003, the makers of three ab stimulators -- Fast Abs, Ab Tronic, and Ab Energizer --agreed to pay more than $5 million to settle Federal Trade Commission charges brought against them for false advertising claims.
They first came to public attention in the 1970s as a way to supposedly alleviate chronic back pain. Today, inversion boots -- as well as inversion "racks" -- are resurfacing as a way to not only relieve pain, but to tone and condition muscles involved in posture and core strength.
How They Work: The boots, which are really ankle supports strapped to your lower leg, are designed to hook into a "rack" that allows you to invert your body up to 40 degrees. (Think a patio chaise longue that puts your legs in the air while pushing your head toward the ground). For the real pros, the boots are hooked into a rack that literally leave you dangling in the air, your head about 2 feet off the ground.
The Promise: Essentially, the goal is supposed to be to allow your muscles and joints to "decompress" after a day of gravity-crunching compression, plus, increase circulation.
What the Experts Say: "In principle, it's a way of using your own body weight to reverse the effects of gravity -- which does work, temporarily. Unfortunately, the minute you resume your normal position, all the effects are lost," says Varlotta. Moreover, he adds, that to gain lasting results, the amount of time you would have to spend upside down would be dangerous.
Bryant agrees. "For the chronic back pain sufferer, it might be worth a try, but under no circumstances should it be considered a long-term fix," he says. And, he says, anyone with high blood pressure, diabetes, or whose backaches are caused by excess weight should never use an inversion boot or table.
"This can cause a kind of increased pressure, particularly in the ocular [eye] area, that can be especially dangerous for people with these health problems," says Bryant.