This is the one I was dreading ! 6 weeks ago I struggled to run for 1 minute, now I am going to run for 20 mnutes non stop. Well I did it, yes it was hard, yes it was painfull, yes it was worth it. My breathing was no problem but my calves and shins tried to defeat me. To all of you about to tackle R3, keep remembering the advice given so many times on here "slow and steady" and when it gets really tough "slower and steadier" and you will succeed.