I receive the Shake Weight for a Easter gift . I have be work with it every morning for about a week - be careful with the single arm exercise , as some other customer have warn to do , and I can see a difference in my arm already . the 6-minute work-out do produce a fairly deep burn feeling in my arm muscle , but I have notice that I recover much better while I be take collagen :  Bovine Collagen , 120 capsule  most of the complaint I have read about the Shake Weight would probably be eradicate if a user view the video instruction , which come with the Shake Weight , before attempt to use the weight . it require practice but the Weight do work - if you do .