Originally Posted by Talvi
I was thinking there's no need to roll on the bed - it was only so I could explore the flexibility and range of movement etc in my arm without having to work against gravity. To mimic any movement I'd just "assume" the roll in the movement of my arm. That way the focus is all on the arm movement. Imagine having a camera attached on a frame fixed to a swimmers shoulders. The shoulders would always be in the same place in the shot.
Then I'll assume you are also rotating your head in order to (relatively) simulate head staying still while swimming?