After my first 3 weeks of using the Shake Weight I am getting a bit more stronger and decided to start being more aggressive on my workout.  In order to get a good workout, you have to start getting rough with the weight.  The faster you shake, the more burn you will feel and develop stronger muscles.  In the process the flab under the arms goes away as well.  So far, I recommend this for anyone trying to tone their arms without putting on to much muscle.