I see the infomercial for this and finally decide to buy it and try it , make a New year resolution to tone up my 50 year old arm . I just finish the 6 minute dvd workout and boy do I feel energize and already slightly tone from just the first workout ! the `` shake '' be generate by you so there be no battery involve . the safety instruction caution to use proper form and not let the barbell `` bobble '' . I must admit , use proper form be much easier on my right arm than the leave since I be dominant and stronger on the right side . after read some of the negative review , I can only conclude that those dissatisfied either do not read the safety instruction or do not follow the dvd workout . I do both . of course it go without say that no gadget will do the work for you : you be responsible for put forth the effort and on a consistant basis . tv informercial tend to lead people to believe that all they have to do be buy the product and hold it in they hand and it will do the work for they ! nevertheless , I think the workout be pretty easy . as for visible tone result , we 'll see what happen after a few week of persistant use . I do like it though !