Externally rotating your upper arms might just be the thing that causes shoulder pain for your students. Fasten your seatbelt and watch this video – published in 2017 by a very experienced yoga teacher, PhD, and physical therapist with more than 45 years of teaching experience to learn the details.
2013 documentary (German TV) about yoga and injuries. The following video features Dr. Günter Niessen, medical doctor, orthopaedic surgeon, physical therapist, Aryuvedic doctor and yoga therapist. He talks about common injuries that brings yogis to his practice. I find the numbers he reports quite shocking .. see for yourself. Available in German language only.