Several weeks ago, a major monthly magazine on women’s health and fitness contacted me to see if I would do a small-scale research study on a Shake Weight exercise program.

Several weeks ago, a major monthly magazine on women’s health and fitness contacted me to see if I would do a small-scale research study on a Shake Weight exercise program.


After telling the editor that I had never heard of Shake Weights, she explained that they are light dumbbells with movable end sections that vibrate when you do a shaking action with your arms. I agreed to enlist six young women and have them perform the prescribed Shake Weight workout two or three days a week for one month.


After receiving the Shake Weights and workout video, I tested all of the study participants in three areas associated with upper-arm muscle strength and size.


The first test was conducted with a force platform, and it measured bicep muscle strength in a carefully controlled (90 degrees of elbow flexion) maximum isometric contraction. The second assessment was a tape measure circumference reading of the upper arm in a bicep-contracted position (90 degrees of elbow flexion). The third assessment was an ultrasound measure of the fully contracted bicep muscle thickness at 90 degrees of elbow flexion.


Once all of the assessments were completed, we started the Shake Weight program. Three of the women trained on Mondays, Wednesdays and Fridays, and the other three trained on Tuesdays and Thursdays. Every training session was the same, as the participants performed the 10-minute Shake Weight exercise program in unison with the instructor in the workout video.


Three women completed 12 training sessions (three days per week for four weeks) and three women completed 8 training sessions (two days per week for four weeks). In addition to shaking the special dumbbells, the women performed several standard arm exercises, including arm curls, overhead arm extensions, shoulder presses and tricep kickbacks, exactly as demonstrated on the workout video.


Although the standard exercises are effective for increasing muscle strength and size, the use of the same dumbbells for four weeks of training lowered my expectations for attaining measurable improvements. After all, the major premise of strength training is to gradually increase the exercise resistance to provide a progressive stimulus for muscle development.


All of the participants completed the program and performed each exercise session enthusiastically. Some felt the workouts were more challenging than others, but everyone trained to the best of her ability.


After one month of training, I re-tested all of the program participants in the three assessment areas. I was quite surprised to discover that the brief Shake Weight exercise program elicited improvements in the women’s arm strength and muscle size. On average, the six participants increased their bicep muscles’ strength by 5.1 pounds for a 12 percent improvement; they increased their upper-arm tape-measure circumference by .4 inches for a 4 percent improvement, and they increased their fully contracted bicep muscles’ thickness by 2.9 millimeters for a 10 percent improvement.


Apparently, the relatively brief training program with a light Shake Weight dumbbell was sufficient to produce some degree of muscle development in our study participants. Although the 12 percent increase in muscle strength is quite modest compared with average strength improvements using Nautilus machines and other forms of progressive resistance exercise, the results of this study indicate that the Shake Weight workout may be effective as an introductory program for conditioning the upper arm muscles.


My first advice to the manufacturers is to sell a set of three (or more) Shake Weights with progressively heavier resistance (e.g., 4 pounds, 6 pounds and 8 pounds) to enable exercisers to systematically increase the training workload for continued improvement.


My second recommendation to the Shake Weight company is to include three (or more) training videos with progressively more challenging workouts (e.g., exercises, repetitions, sets, etc.) as participants attain higher levels of muscular fitness.


For best results, regardless of the equipment used, strength exercises should use a resistance that fatigues the target muscles within eight to 12 controlled repetitions (between 50 and 70 seconds), for one to three sets, performed two or three nonconsecutive days a week. When 12 repetitions can be completed with correct exercise technique, the resistance should be increased by about 5 percent.


Wayne L. Westcott, Ph.D., teaches exercise science at Quincy College in Massachusetts and consults for the South Shore YMCA.