Negative or positive splits? A post race analysis

Negative is sometimes positive...

Last week I was writing that Bergen City half marathon course is perfect for negative splits. I was pretty sure that I had a negative split during the race. However, when the detailed results came out a day or two later, I was surprised to see that I had a pretty even split. How come? Was it good that I did the hills as slowly as I did, after all? Or were the first 2-3 flat kilometers just too fast?

OK, let's start from the beginning. A split is simply the half distance of your race. You have a negative split if you run the first half slower than the second half, and you have a positive split if you run the first half faster than the second half. Most of the advice directed to runners advocate for negative splits, even for short races. The importance becomes more as the races become longer (either in time or in distance). The point of a negative split is to start out slowly enough that your heart rate does not go close to lactate threshold in the beginning. You do not start wearing out your glycogen stores until you have made a substantial part of the distance. Then when you reach the critical point of your race, towards the end, when your body is really going low on all energy sources, you still have some left to finish the race gracefully.

In fact it was a marathon pace calculator that I found online that first made me start thinking that I could perhaps run a marathon in a not too embarrassing time. That calculator says that you can run a marathon in just a few minutes more than twice your half marathon time. Provided that you do the training towards it of course. It also gives you an exact heart rate and pace plan to follow throughout the race, with a clear negative split. All my own experience during training for long runs also gave me an indication that negative splits were most natural for me. For long slow runs, I normally start out with pace 6:30 and usually end with pace 5:45 quite naturally, without even pushing. Even for short races, like Stoltzekleiven, I know that if I start out too fast, I get punished in the end (although my split is always positive there no matter what). Many faster friends have also told stories of how they got much better times in uphill races when they managed to keep it slow in the beginning.

With this background I was pretty surprised when I found out that  I had run the Bergen City with an even split. OK, it is in fact a little bit negative, but with a pace difference of merely 5 seconds. Then I studied the splits of many of my friends, and indeed in Bergen most people have a negative split; the course is very natural for that. But whether or not negative split is the best strategy to get the best finish time is much debated. It is the best strategy to have a good race experience and to be able to finish in good shape, but is it really best for achieving best possible time?

Looking at statistics of the finish times of long races, by far most people run with a positive split. Of course amateurs make the mistake of starting out too fast and then losing a lot of time at the end, but even pretty fast amateurs mostly run with a positive split. Real elites, though, run mainly with negative splits. But what is best for an elite is probably not what is best for me. First of all I run for quite a lot longer time than the elites of the same race, so regardless of how I start I will get very tired in the end. Those who argue against negative splits for amateurs explain it with what is most intuitive: you will get tired in the end no matter how fast or slow you run in the beginning, so just run when you can and make as much distance as possible. But I know that this strategy fails if you push too hard in the beginning. I have seen so many examples of it, including myself.

Thus I am now a little bit lost. I like to analyze what I did right and wrong during a race, and now I am really not sure about the Bergen City half marathon. When I was reporting to you last week, I was thinking that I was too slow up the hills. Now, I am wondering whether I was simply too fast in the first 2-3 kilometers during the flat part. I felt no exhaustion what so ever during that first part, and when the hills came I slowed down and felt good all the way, but perhaps the start got my glycogen going too soon anyway. Or perhaps I am right to think that I was too slow up the hills, I could have saved a couple of minutes there, and still manage the last part as I did. It is not easy to know. One thing is for sure, I was not as exhausted at the end as I was in Oslo one and a half years ago, so I could most probably have gone faster. But if I could, then why did I not in the second half? Was I a bit too afraid for what was yet to come? Was I just not determined enough this time? Or was this exactly the right time for me at this point?

So many questions, so few answers...