In the second one I offsetted the keys to add overlap, also adding ease in and out of the move:
And in the last one I pushed the extremes and actually pulled the key for the lower arm to hit the extreme the same time as the upper arm, just dragging back the hand and fingers, but giving a greater build up to each move:
It's a simple little exercise, and I didn't have time to move the rest of the body at all. I just wanted to focus in the arm. I think it's pretty successful.