Now, I may be teaching my Grandmother to suck eggs with this one, but it's been such a revelation to me I wanted to share.
When running up hill, instead of swinging your arms to the back, swing your hands up, towards your face. I'm gobsmacked, it may just be a distraction technique, but it WORKS! Well, it does for me anyway.
Give it a go, I'd be really interested to see if it works for anyone else.