No! But you do want to ensure that you are working your muscles and feel the ‘Slendertone Sensation’! When you first put on the product and turn it on, you are at the lowest setting. As you increase the intensity (to level 25 and beyond), the sensation goes from a tingly feeling to a distinct muscle contraction and relaxed state. These feelings will alternate. It feels like you are tightening/flexing and then releasing/relaxing your muscles. This is good - because feeling the muscles work lets you know that the product is doing what it is supposed to! It is very important to strive for this distinct feeling, to ensure that you get a full workout.
As you advance, your muscles will get stronger and firmer, and you will get accustomed to the feel of muscle conditioning. Be sure to periodically increase the intensity to always feel the Slendertone Sensation!