Is it more efficient to have a low or high arm action for middle/long distance running?
I don't claim to know the answer, but I doubt that there is one answer that applies to everyone. I think that your job is to find the action that is most efficient for you.
one thing I do find it interesting to think about is that when I am doing proprioception drills, I concentrate on my arm position as a way of controlling my speed. lower is slower, for me, at least.
then one day I was watching a 10,000m race with Brendan Foster doing the commmentary and he noted that the runner in 2nd place, who I seem to recall was Craig Virgin, had lowered his arm position slightly, and Brendan said this indicated a loss of concentration. to me it was a control thing, but to Brendan Foster it was a concentration thing.
I also think it interesting to think, as Denbigh suggested, about the role that arms play in changing pace. in his book Peter Coe, a non-runner, said that faster arms make faster feet, while in his book The Art of Running Faster, Julian Goater (13:30 for 5km and British X-country champion) said the exact opposite, that faster feet make faster arms. as a coach I teach lads to think of their upper body as their gearbox. to change pace you should shorten the stride and increase the cadence by driving with the arms. I guess that puts me in the Peter Coe camp.
cheers.