Summary: Have been using Cardio Gym for about 2 weeks now. I don't know what the median age for most of these reviews is, but at 44 and in good physical condition the game is pretty hard on the joints. I've breezed through the Wii Fit and wanted something more challenging to add on. After 2 sessions of trying to bounce and rock with the footwork as they directed my knees were in severe distress. I've modified by just rocking and hasn't been too bad.