My experience with a rotator cuff tear (RCT) came from weights, but these injuries develop from a range of causes (http://www.mayoclinic.com/health/rot...SECTION=causes) including repetitive stress.
Fortunately a therapist (my brother) recommended some focused exercises which I do preventatively to this day.
So far, so good.
An orthopedic surgeon I was deployed with explained the anatomy of the shoulder and why it's so vulnerable to injury.
The anatomy also explains the value in exercising, keeping the four muscles toned and healthy to reduce injury risk. I found an excellent article at Bowsite, http://bowsite.com/bowsite/features/bowdoc/shoulder/ -virtually the same explanation from my ortho friend years ago.
The Bowsite article is excellent. Of the recommended stretches and exercises, I do a lot like the fourth photo (external rotation) in the gym, but it can be done with resistance bands. Bands or weights are handy because you can also flip to internal rotation for exercising.