Arm Placement, Breathing & Vo2 Max

I'm experiencing something interesting regarding my arm placement. I've struggled a bit finding the most comfortable placement for my arms. Recently, I've been placing my arms a bit lower, very similar to the arm placement of Ryan Hall (http://www.youtube.com/watch?v=QbKp2HeUpkY). I read that Ryan Hall's dad tweaked Ryan's arm placement based on his study of kinesiology and studying other athletes with similar body types who possessed the same basic speed, and particularly Hicham El Guerrouj (Hicham and Ryan have similar body types to mine . . . I'm 6ft. and just a few inches taller than both). El Guerrouji runs with his hands down, low and relaxed. During Ryan's long runs, his dad would ride a bike along side him and periodically check Ryan's exertion level using a heart rate monitor. What he found was that as Ryan lowered his arms, even later in tempo runs, his heart rate would go down. Even later in tempo runs when your heart rate should be higher because you are more fatigued, his heart rate would go down as he lowered his arms.

So based on this I lowered my arms and it's been pretty successful. However, today I did a 3x1 interval session, meaning I ran three 1 mile intervals at 6:10 pace, 6:00 pace and 5:50 pace with 400 meter recovery in-between. For whatever reason, I raised my arms during the 1 mile intervals more in the position that you see the East Africans (for example, see Haile's arms at the 2:39 min. point in the video: http://www.youtube.com/watch?v=QbKp2HeUpkY). When I raised my arms, my breathing was easier and more controlled. I didn't have a heart monitor or Vo2 max monitor but I was breathing so much easier and to the point that the 6:00 min.per mile pace wasn't that difficult for me to hold and I didn't feel like I was pushing my hardest. I lowered my arms and I felt like my breathing was more difficult . . . I could it but it was more taxing to hold that pace.

My question is does anyone have any experience in this area and/or could point me in the direction of some good articles? Also, any personal advice or experiences are welcomed. This is new uncharted ground for me as I started adding interval and tempo training a few months ago and now I'm running at paces I never dreamed of so this is all new areas for me. I'm starting to comfortably dip below the 6:00 min. per mile pace range and I'm able to hold it for 30 minutes or so.

Or, is this just an individual thing that I'm over-thinking? Before I just do what feels good, I want to know if there's some medical or other data on the subject.

Given that I'm 40 yrs. old, I'm sure I'm in the neighborhood where my improvement will level out but now I'm looking at specific intricacies of running like arm placement, breathing, improving Vo2 max levels, etc., as it may lead to more efficient running or shave a few more seconds off my pace.

HHH