I buy one of these , watch the dvd and do some of the exercise and my right shoulder have suffer immeasurable damage . my shoulder grind and click when my doctor put I through basic test . I be take chondroitin now which seem to be help after no success with cortisone shot but the un-natural stress and torque this apparatus put on you shoulder be terrible beyond word . I have not be able to golf for a year as a result and I have never be more unhappy with a single product in my life .