This began as an exercise based on page 233 of The Animator's Survival Kit, where it showed how to get a fluid look when animating jointed objects. The trick is something like cracking the joints like a whip, where the base (here, the upper arm) moves first, followed by its secondary parts. I suspect dancers use a similar trick to achieve fluid movement. I gave the guy one "whip" arm and one stiff arm to highlight the difference. Of course I had to get a little silly.