Before you purchase your next piece of exercise equipment, start your next diet plan, or join the new gym that promises results in just 20 minutes a day or just one workout per week, look at the science behind the claims.
It seems that the Shake Weight people have a study that “conclusively” shows the benefits of their product. The authors of the study conclude:
It takes 7 times as long to expend the same total energy with a traditional dumbbell, or one must use a dumbbell 10 times as heavy
The Shake Weight is a total body energizer
The Shake Weight generates higher peak forces in the main muscle groups
The frequency of contraction is much higher in a Shake Weight
The Shake Weight study authors chose to compare the Shake Weight to a typical 2.5-pound dumbbell. Anyone attempting to burn fat, build muscle and “tone-up” by lifting 2.5 pounds better be in for the long haul. Real research has shown time and time again that loads requiring 60 percent or more of your maximum effort are required to exhibit strength gains and thereby cause muscle hypertrophy (growth). Only in rehabilitation settings would someone encounter a program that involves lifting only a 2.5-pound dumbbell.
In terms of being a “total body energizer,” shaking the Shake Weight does require more movement from the muscles in the body than doing a traditional bicep curl. Does that mean it’s more effective? Absolutely not. One important principle states that the training effect is specific to the area worked, i.e., a bicep curl is meant to work the bicep, and will have no effect on leg strength. Unfortunately, the Shake Weight study authors believe that it’s a positive result for their product to have a “side effect” of working more muscles than it should.
In terms of muscle activation and frequency, it is understandable that the Shake Weight shows constant activation, because the muscles are constantly contracted when using the Shake Weight. When compared to traditional strength training, there are points in a movement where there is more or less force being applied (due to gravitational effects and lever dynamics). The important question to ask is whether increased muscle activation, specifically the type of activation that occurs under constant contraction, is more beneficial? In the case of the Shake Weight, activation does not equal results.