A new device that has exploded onto the market is the Shake Weight™,
a 2.5-pound dumbbell-shaped apparatus that promises “strong, sexy, sculpted arms & shoulders” in just 6 minutes a day. The product was originally designed for arm-conscious women, but a male version has recently entered the market. Users grip the tool in one or two hands and then shake it vigorously back and forth with minimal—if any—changes in range of motion.

The Shake Weight website states
that strength benefits are derived from
a “new” technology dubbed “dynamic
inertia,” which promises greater muscular
activation than traditional dumbbells. The ads show finely chiseled models pitching the tool, advocating its effectiveness. But can a 2.5-pound dumbbell really help the average, overweight American develop lean, toned arms? You decide. According to information provided in the 2010 edition of ACSM’s Guidelines for Exercise Testing and Prescription (8th ed., p.169; Baltimore: American College of Sports Medicine), “To improve muscular strength, mass, and—to some extent—endurance, a resistance exercise that allows a person to complete 8–12 repetitions per set should be selected.” Older adults or deconditioned individuals should select a level of resistance that allows them to complete 10–15 reps.

The Shake Weight website claims that users will perform roughly 240 reps per minute; that’s up to 1,440 reps, if the 6-minute suggested protocol is completed. However, based on scientific principles, the applied resistance is not significant enough to solicit the promised muscular adaptations. Other factors to consider are fat mass, which will conceal muscular tone, and limited range of motion, which may initiate degeneration of area soft- and hard-tissue structures.
While the Shake Weight may help a deconditioned population move—or shake—more, can it deliver on its claims? You can shake it to your heart’s content and find out firsthand for $19.99.