TLDR;

• Starting too fast too early may wreck your marathon by as much as 60-minutes based on data from more than 400,000 Chicago Marathon finishers.
• Going out too fast also makes you much more likely to hit the dreaded wall later in the race; over 50% of Chicago Marathoners who hit the wall go out too fast in the first 5k.
• And yet lots of people continue to go out too fast; almost 40% of Chicago Marathoners have the first 5k as their fastest race segment. Women and older runners are slightly more likely to do this but ability and experience play a major role.
• Starting more conservatively can improve your finish time; about 10% of Chicago Marathoners run the first 5k as their slowest of race and they gain a whopping 50 minutes on those who’s first 5k is their fastest. And, according the data, none of these slow-starters hit the wall!
• This is part of a series of posts that I am writing as part of an ongoing analysis of marathon data. So if you are interested in this sort of thing then you will find a growing number of articles here.

Seriously. Don’t Go Out Too…