Subacromial pressures vary with simulated sleep positions: Journal of Shoulder & Elbow Surgery, 10-10; Werner et al..
The researchers studied subacromial pressure in subjects side lying, prone, and supine. Both the side lying & prone positions place at least one arm in an abducted and/or internally rotated positions for 8 hours at a clip. Not suprising they increase subacromial pressures greater than the supine posture. The authors were studying this in the context of the post surgery environment, but I think it's safe to assume the same happens in the throwing athlete recovering from a tough day of practice.
It's interesting when 2 years ago researchers were studying sleeping posture relationship to kidney stones, the side lying position was again implicated in 88.2% of patients.
But yet the side lying position is often advocated in patients with low back pain, and the back to nature primal enhusiasts.
I don't know, when I sleep I'm flopping all over the place like a fish. Does anyone know if a sleeping position can be taught?