Kettlebell Snatches and Shoulder Health

First wanted to let you know that "Power to the People" and "The Russian Kettlebell Challenge" are great. Now on to the question.

Today I was trying out the one arm snatches at the gym for the first time (with a dumbbell). A personal trainer walked over and asked me what I was doing. I explained and she proceeded to warn me that I could mess up my shoulder by swinging the weight back between my knees like that... something about stretching the tendon.

I didn't give to much weight to what she said, but I said thanks and went about my business. However I would like to hear your sports science response, so I can have it ready to go next time I get a question like that.

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