Economy of movement

I've taken to looking through the published articles archive of Dan Lieberman, a Harvard professor in human evolution. The first paper I looked at was one of his most recent: "Control and function of arm swing in human walking and running". It is the findings of a study that attempted to determine what role the arms play in running and walking - are they active (do they help propel), or are they passive (do they act as mass dampers, or to balance the movement of the legs for want of a less technical description)?

Turns out that they believe the arms are passive (read the article for a slightly more technical description), and are not used to help propel you. So all that excessive arm swinging is not going to help you run faster - you're better off letting your upper body move naturally. A while ago I experimented with different arm positions and swinging techniques, and discovered that if I kept my elbows bent at greater than 90 degrees and close to my chest, and didn't try to actively swing them, it felt more comfortable and efficient. So I'm sure Dan would be relieved to know I agree with his findings. Now he can sleep much easier.

I was a big arm swinger when I first started running

Are you a running windmill? How do you move your arms when hitting the street?