I recently have a serious back surgery and I be always look for new thing to keep I motivated exercise as it be very important for I to avoid further back problem . the novelty aspect of Shake Weight Dumbbell attract my attention . this weight be a molded plastic handle with a spring at each end that compress and extend as you shake it back and forth . I like they because they add a bit of variety to my exercise routine . however , they be not provide a harder workout or burn more calorie than the traditional weight . a recent consumer report -lrb- July 2011 -rrb- do electrocardiographic study to judge how effective the Shake Weight system be and find that it be not any better than traditional weight . it do not not mean you should not use these weight , the study just clarify that it be not a magic bullet . any resistance exercise build strength and any movement build calorie , and so do Shake Weight system . if the novelty of Shake weight get you exercise it do its job !