I learned the hard way that there are 2 tendons that run up into your shoulder that connect your biceps muscle. Whenever I do any bicep exercise that extends my arms back and/or up (overhead cables) it restricts those tendons as they are working and after a while I get tendinitis. It took me a long time to figure out what was going on because I always thought it was from doing shoulder exercises (may still be a factor), but the biggest culprit in my case was the bicep exercises I was doing. I also stopped doing any kind of shoulder pressing that pulls my arms too far back, such as behind the neck barbell presses. My situation may be really unusual, don't know, but I do know most guys never realize their shoulder pain can actually be bicep related. I learned the hard way.