Are there any techniques like in the 100m it is often said to exhale as you come out of the blocks. Could there be any breathing techniques that may help? I have been told to try to inhale through the nose and exhale through the mouth while runnning
Over such a long distance any breathing technique that keeps you relaxed will help. I guess this would equate to a rhythmic breathing pattern which is in time with the rhythm of your running.
You should still exhale while coming out of the blocks.
Hope this helps,