Designed to maximize the body's senses to make you more coordinated and stronger, simply trying to keep the ActivMotion bar parallel to the floor while moving side to side (like skating) will train your under-active stabilizer muscles. The bar pulls you in the direction it's moving so your body has to cope by contracting core muscles and maintaining balance and stability in every movement you do with it. The ActivMotion fitness bar is a hollow bar with rolling weights inside to make it unstable when in use. Users need to try to keep the rolling weights in the center of the bar. The maximum weight of 18 pounds may not seem like much but if you're not seriously fit you may discover that you need a lighter bar, which starts from 6 pounds. Get one of the multi-bar bundles to expand the variety and intensity of your workouts. The most popular is the 10-pound bar.