Just as one reviewer mentioned before, I am getting no workout with my abs using this. It seems the majority of reviews are positive for these types of devices, so I would guess that I'm somehow using it wrong. The instructions are fairly simple. Sit on your knees, raise up, and roll the wheel across and then pull it back. How this gets your abs engaged is a mystery to me. My arms were getting a workout because they had to support my weight at the end of the extension. My back partially felt some stress as well. I tried multiple ways of using this device, but no matter how many times I tried, my abs never felt stressed.