the shake weight do work ! but only for specific goal . this will increase muscle size and strength in weak individual . this will decrease muscle size and strength in those who already use they biceps\/triceps . it be that simple . my girlfriend use this and claim `` I can feel the burn '' not realize what actual body building\/muscle grow be all about . she be simply fatigue she muscle and since she be so weak , it appear to work . so do the shake weight work ? yes , it can work . but you be better off get a pair of dumbbell , 20lb each , and work you way up to increase the weight . just go to bodybuilding.com for a couple month at least 4 time a week and you will learn a lot about body building , loose weight , etc. . I only give this 5 star because it be a high quality product but a bad idea , like most popular thing you see on tv . by the way , you can get some cardio in by use the shake weight and jump around or do some squat with it , yes 5lb squat while jack off the air behind you head .