Purchased the Ab Circle Pro and after putting it together noticed that they had included extra knee pads as a sort of "patch" for knees hitting the bolt that connected the attached pad. Using the extra pads caused the user to slip off of the machine causing possible injury. After using the machine for a few days my wife and I noticed back pain from using the machine. Visited a Chiropractor who suggested that we stop use of the Ab Circle Pro and the back pain is gone. My advice is DON'T buy it, and if you have one that... read full review »