Originally Posted by Doubles
Rafa, Berdych, Isner, Querrey, Verdasco, Almagro, Ferrer, Tipseravic, and others all use poly. I use poly, at various tensions, I'm not a pro, I don't have perfect technique and I've never had arm injuries. Saying that poly will give you an arm injury is just as much of a sweeping generalization as saying it won't. It all depends on the person.
Keep playing with poly for another 20 years and see how much of an arm you have left. Tennis elbow is a repetitive cumulative injury as the micro tears in your tendon slowly get bigger and takes longer to heal each time you hit the ball.
Smoking doesn't cause cancer when you first start smoking either, but keep smoking for 20-30 years and see what it does to your lungs. Would you start smoking today just because you won't get lung cancer until 20-30 years from now? I assume not.