Chaturanga Dandasana is typically one of the more overlooked and rushed postures during the transition to Upward Facing Dog. This is an important pose to refine because of its repetition in the vinyasa style yoga classes. The tendency is to not use proper muscular engagement and/or lower too far into the pose; An acute angle in your bent arms, combined with a lack of support, increases the potentiality of placing unnecessary compression into the structure of your shoulders.
Contrary to the belief, refining your Chaturanga is more than just building upper body strength. When you practice recruiting your core muscles and engaging your body more evenly, you're stabilizing your entire shoulder area as well as properly preparing for the next transition (upward facing dog pose). In addition, when you bend your elbows to 90 degrees, (keeping your shoulders slightly above your elbows) you're stacking your joints, not collapsing in your chest, and therefore, lessening the strain in your upper body. If you're in the early stages of experimenting vinyasa into your yoga practice, you can always modify this pose by lowering both of your knees down to the ground as you gradually build strength!