I Hi Dr. Rynne, Thank You In Advance For Answering

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Hi Dr. Rynne, Thank you in advance for answering my question. I was told by my doctor to roll a tennis ball between my shoulder and a wall. It is to cure or alleviate slight pain from a rotator cuff problem. In my normal daily activities I have no pain because only in certain positions is there any discomfort from my shoulder. My question is how many minutes or seconds should i rub the ball against the wall. I do it in three parts: the back of my shoulder, the top of my arm & then the back of my shoulder. Appreciatively, Betty