Weighing in on the Shake Weight
Of the hundreds of exercise gadgets that have graced TV airwaves over the years, only a handful ever become big-time sellers and even fewer become cultural phenomenons. The Shake Weight is definitely in that rarified category. Over 3.6 million people have watched the Shake Weight ad on YouTube, and millions more saw the device featured on "The Ellen DeGeneres Show" and spoofed on "Saturday Night Live."

If you've somehow missed the hoopla, an introduction is in order. The Shake Weight is a 2.5 pound dumbbell-shaped device with spring-loaded weights on each end. Instead of simply lifting the Shake Weight, users are instructed to grip it with two hands and shake it up and down as if priming a bottle of soda to explode.

The company behind the Shake Weight, FitnessIQ, recently released a Shake Weight for Men. It works like the original version, but it's twice as heavy and there's more resistance in the spring-loaded weights.

Shake Weights are sold in drugstores and department stores everywhere. The women's version costs about $20. The Shake Weight for Men costs about $30.

Claims: The TV ad trumpets the Shake Weight as "the revolutionary new way to shape and tone arms you'll love." The ad claims that the device is "based on a completely new workout technology called dynamic inertia that ignites the muscles in your arms, shoulders and chest." Thanks to that dynamic inertia, you can supposedly "work out your entire upper body in just six minutes a day." The ad also says that "studies at a prestigious California university prove that the Shake Weight increases upper body muscle activity by more than 300% compared to traditional weights."

A video on the Shake Weight for Men site says that the device "is going to kick your butt in just six minutes guaranteed." How? It "harnesses the power of dynamic inertia to totally redefine strength training" and "forces your muscles to contract as many as 240 times a minute." The video goes on to says that "six minutes with a Shake Weight burns as much muscle energy as 42 with a standard dumbbell."

In a phone interview, Johann Verheem, chief executive of FitnessIQ and inventor of the Shake Weight, called it "a whole different approach to exercise" that "uses velocity instead of a dead weight." He also said that his device will "tone, tighten and strengthen" the entire upper body.

Bottom line: The Shake Weight owes much of its fame to the unusual technique it requires of users. But does it work?

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.

I'm not exactly a fixture on the weightlifting circuit, but, in the name of healthy skepticism, I did try out a Shake Weight for Men provided by FitnessIQ. After about 10 seconds, both of my arms tensed up into a steady contraction. It felt like I was flexing everything I had. After 30 seconds, I was ready to quit.

Could I get a total upper-body workout in just six minutes a day? I'm pretty sure I'll never find out.

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