I saw a ad for these on Youtube. I want to pick one up but worried I would end up like this guy. I can do Planks but not over 30 seconds. There are mobile games to challenge your mid section or core worried it might be hard on my knees or feet due to the twisting. Someone on Amazon said this thing is brutal so I might stay away from it. Comes with 4 free games the rest are acquired with a sub.