TLDR;

An analysis of more than 215,000 London Marathon runners during the period 2011–2016;

How do runners pace the London Marathon? Where are the fastest and slowest sections of the race?

How does the pacing of elites compare to recreational runners and those running a PB?

Putting what we learn into practice we create an optimal pacing chart for recreational runners that is tailored for London.

Introduction

With the London Marathon just a few weeks away, participants will be planning their pacing strategy for race-day. Many will look to pacing charts to take some the guesswork out of race-day pacing, but the one-size-fits-all approach of traditional charts limits their usefulness in practice. In this article we describe a new type of pacing chart that is optimised for a particular marathon course — in this case the London Marathon — to provide participants with fine-grained, tailored pacing advice, based on the pacing patterns of the best of the best.

The data for this study is part of a larger dataset of 1.7m race records from more than 60 city marathons, London among them. The London dataset includes the last 6 marathons (from 2011 to 2016) and includes 215,575 race records, each with 5km split-times.

The Problem with Existing Pacing Charts

Marathon pacing charts aim to take the guesswork out of pacing, by calculating various split-times for a specified target finish-time. For example, the Runner’s World Pace Charts list the times for various points in the race (5km, 10km, halfway etc.) for a wide range of paces and finish-times, from 3 mins/km (just over 2:06 finish) to 11 mins/km (a 7:44 finish).

Convenient as they might be, these charts suffer from an important shortcoming because they assume even pacing throughout the marathon. In practice, even pacing is extremely rare for a variety of reasons, not least because of athlete fatigue and course conditions. Consequently race-day finish-times typically deviate from chart-times for all but the most disciplined of runners.

More sophisticated pacing charts have been developed, which go some way to modelling more common pacing patterns. For example, pacing charts, such as those at Marathon Basics, calculate split-times based on even pacing and a 47/53 positive split; that is the runner spends 47% of their time running the first-half and 53% running the second-half of the race. While this might be a step in the right direction it remains limited by assuming a fixed split-type. Even when other split-types are offered (e.g. see Running For Fitness) the resulting charts still assume evenly paced splits within each individual half of the race.

We need more fine-grained pacing plans, which account for ability and fatigue of runners and different course conditions. In what follows we will analyse the pacing patterns of London marathoners to better understand how a typical runner completes the course. We will see how, despite the large variation in runners (gender, age, experience, ability), most runners follow a remarkably similar relative pacing profile, which provides a starting point for a more tailored pacing chart.

Pacing the London Marathon

The chart below shows the pacing (mins/km) for men and women during each of the 5k segments of the London Marathon, including the final 2.2k segment. As expected men are faster than women and, for both men and women, pacing tends to slow as the race progresses. The start of the race (the first 5k segment) is the fastest (5.47 mins/km for men and 6.17 mins/km for women, on average) and the penultimate segment (35k to 40k) is the slowest (6.92 mins/km for men and 7.92 mins/km for women); both men and women manage to speed up during the final 2.2k section of the race as they ‘sprint’ to the finish. Thus, the average London participant starts outs fast but then gradually slows, completing a positive split with the second half of the race approximately 15% slower than then first.

A word of caution here, this average pacing profile includes people who hit the dreaded wall in the second half of the race. This means that some of the slow down shown will be exagerated, at least somewhat, by these poor souls.