Why are negative splits in running so important?

Most runners run as hard as they can and as fast as they can when they line up at the start of a race.  This can lead to all sorts of problems as runners and you can end up having the worst run in the world where you hate every moment of it as you feel you have a "bear" on your back. However if you run the second half of a race faster than the first half. you have a good chance of enjoying the run and achieving a pb. The vast majority of world records and other noteworthy performances at distances of 1,500 meters and up are set when runners achieve negative splits, or get very close to it.  Holding back, just slightly is no mean feat, you feel good at the start line, you are rested and tapered and ready for action, so as soon as the gun goes off your off saying to yourself, this is the day that I just hang on and it happens.

Usually it doesn't and you can't fight physiology and it's one the main coaching points that I have to say to all of my runners upon reflection of any run or race "Did you go out too fast?"

So a big shoutout to some RV runners who achieved something rare during the Wyvern 10k on Sunday. 5 RV runners ran their second 5k quicker than their first, it was hot and humid, an awful combination, but they listened to their coach and started off within themselves and all got negative splits on a hard course in the heat; oh and they got PBs as well