Awhile ago, I mentioned a few other runners in my neighborhood, one of whom runs backwards down the street; well, last night he was out running while I was out getting my 3 miler in, and it seems he's added a new part to his routine. He now occasionally flails his arms about while he's running backwards.
I would like to say the maneuver mimics a windmill, but that description would make the action seem more choreographed than it appears. It really just looks like he's flailing his arms about.
I would say that perhaps this elderly man is suffering from some sort of disease or unfortunate failure to control his limbs, except that he doesn't do it all the time. When he runs forward, he stops the arm flailing and just runs like normal. It kinda reminded me of that episode of "Friends" when Phoebe and Rachel go running and Rachel discovers that Phoebe runs like "Kermit the Frog." That is a very close comparison to this guy.