Body Toning Technology, Clinically Demonstrated to Tone, Firm and Strengthen the Abdominal Muscles. When you first start toning, you will feel a tingly sensation. As you increase the intensity you will start to feel distinct muscle contractions. This is when CoreFit (and you) are optimizing your workout. It should not be uncomfortable, but you should feel like you've pushed yourself a little bit harder every time you tone. In Clinical Trials*: 100% of users reported their abdominal muscles felt firmer and more toned after 6 weeks. 92% of users felt that the firmness and strength of their ab muscles have increased. *6-Week Clinical Trial conducted by The University of Wisconsin La-Crosse School of Exercise & Sports Science and published in the International Journal of Kinesiology & Sports Science (2018). 30 Minute Abs Workout 10 Programs 100 Intensity Levels Improved Compression Tones All 4 Abdominal Muscles Fits 24"-42" waist (up to 50" with included Belt Extender) Recommended use: 5 times per week