HSP- You were proofreading your post but missed that months does not have an "e" in it.
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Good back exercises depend on what your trying to accomplish. With my condition, everything I did revolved around pinching my shoulder blades to correct that problem. I don't know names of exercises but in general, pinching the shoulder blades works the muscles with little weight needed. Also, tubing exercises tended to work the back.
I work my back almost as much as I work my abbs and legs-which are more than I work my arms and chest. I feel that this has helped me a ton. What some kids don't realize (and I've only heard this as theory, not definite fact but it seems logical to me) is that if the muscles that deccellerate the arm are weak, tired, etc. it will end up slowing down velocity (if not on one pitch, in time).