Excellent read on shoulder injuries and archery.
I am a firm believer in a rounded physical training regimen. I have maintained for years that shooting hundreds of arrows is NOT good practice. It is better to shoot 24 well aimed shots and then perform other exercises while mentally reviewing the shots made.
I also believe that alternating time at the shooting line and physical training is more beneficial to the body and mind than drilling every day. Of course, there are those beautiful days when it is too tempting to skip a day but good training will help prevent an injury even should you over do it.
http://www.grandviewoutdoors.com/bowhunting/articlecontent/7/2011/2663/bow-hunting-and-shoulder-pain-part-1