This is a great little gadget to beef up the forearm in an original way. I do not know if it is really possible to rehabilitate because it requires some strength and skill to keep it in rotation, the hardest being the "run" (after a few tries we take the hand: all persons have tried to make it work arrive after a longer or shorter time ...).
Negative: the counter !! My first order was referred to Amazon because the counter was not working. So I ordered a new powerball "neon" for the LEDs when it turns. But on this latest model also the meter does not work well (it stops or indicates anything). Yet this indicator would be quite useful. Too bad the problem so common.