I do not think this can replace work out but I do believe it compliment a workout very well . that be say I goof around with the female version of it for a few minute when I buy it for my wife and my arm be sore the next day , you can definitely feel the pump if you use it the right way . I be definitely go to order the male version of this . again it will not replace work out but it be a definite plus to add to a exist routine ... bring out that much more muscle definition that you just can not get on you own !!!  Shake Weight Dumbbell