Running negative splits in a race is no mean feat. Being able to pace yourself throughout a run with your split times slowly getting faster is one of the things that separates the elites from the rest of the running pack. But just how hard is it? Well, we set 4 Running Channel friends and presenters the challenge of running a 5K distance, with each K being faster than the previous one. Find out how they got on. How do you think you'd do with this challenge? Do you have any other challenges that