Originally Posted by
Tyche
On race days, even in the marathon, you can run a faster pace at an easier perceived effort. I'm sure there's a ton of factors that contribute to that, adrenaline, mental status, etc. The reason people have a hard time with this in the marathon is because they feel good about themselves and attempt to pick up the pace and end up crashing at the end. You can typically get away with it at the shorter distances without too much repercussions. I actually pace myself 10% faster than goal pace during the first mile of 5k races and try to sustain it. If you attempted to do that in the first 1/3 of a marathon, you'd likely fall on your face at the end.
Edit: I doubt you'll hit the wall with a run/walk strategy, really depends on your diet in the week leading to the race, but I doubt it.