Yes, Shake Weight infomercials are hilariously porny. But do these thrusting, phallic dumbbells work as advertised? The L.A. Times did some digging:
Daniel Cipriani, an associate professor of exercise and nutritional sciences at San Diego State University, says the device can definitely give a person a good workout and probably would tone and strengthen arm and chest muscles, especially in people who are fairly new to strength training. People who already lift weights regularly "probably wouldn't see much benefit," he says.
Cipriani led the study mentioned in the TV ad. With funding from the company, graduate students in his lab measured the muscle activity required to use a Shake Weight and compared it with standard curls with a dumbbell of the same weight. (Cipriani says he has no current financial ties to the company.) As the ad claims, the Shake Weight did, in fact, require about 300% more muscle activity than the dumbbell. "Using the Shake Weight really got muscles fired up," he says. He adds that not many people can use the device for long without getting exhausted. "I could see someone using it at their desk for a three-minute break. I don't see it as a main form of exercise."
There's no doubt that moving a Shake Weight is hard work. But David Swain, a professor of exercise science at Old Dominion University in Norfolk, Va., isn't convinced that it's really an exercise breakthrough. In his opinion, it's "unrealistic" to think that a person could get a full upper-body workout in just six minutes a day. Even if a person used the device that long, there's no evidence that it would provide anything close to the benefits of a 30-minute workout with normal weights, he says. Users hoping to get rid of arm flab will be disappointed, he adds. "Spot reducing — losing body fat from a particular region by exercising that region —is a myth."
And "dynamic inertia"? Swain had never heard of it. "It's obviously just a phrase they invented for marketing the device," he says.