How to run a Boston Qualifying Time at the 2018 Chicago Marathon

An analysis of BQ times and pacing strategies in the Chicago marathon.

Introduction

In this post we use results from the last 13 years of the Chicago Marathon (2005–2017, inclusive) — 465, 052 runners, including 257,308 males and 207,744 females — to explore how often participants achieve Boston Marathon qualification (BQ) standards, answering the following questions as we go:

  1. How often do male and female runners of different ages achieve their BQ times?
  2. When they achieve their BQs, how much margin do they typically enjoy and is this influenced by age?
  3. When runners fail to achieve their BQ time, how much do they miss by, and is this influenced by their age?
  4. How do the pacing patterns of those who achieve their BQ times differ from those who miss theirs?
  5. Are some pacing patterns (e.g. positive vs negative splits) more commonly associated with BQ times than others?

At the end of this article we will provide specific pacing advice, for male and female runners, across the different age groups, as to the pacing targets they should aim for in order to achieve their BQ time. This advice will be based on the typical pacing patterns of male and female runner who sucessfully achieve their BQ times in a given age-group on the Chicago course.

The Boston Marathon Qualification Standard

With the 2018 Chicago Marathon just around the corner many participants will be giving careful consideration to their desired goal-time and their pacing strategy as they aim to get the most from Chicago’s flat and fast course. Most participants will have their own personal goal-times in mind, and many may hope to achieve new personal-bests. Some may even hope to secure a much sought after qualification time for the Boston Marathon.

The Boston Qualification (BQ) time is one of the marathon’s best known, and most desirable, ‘good for age’ standards. It is based on the age and gender of runners. The chart below shows the qualification standards for the 2019 Boston Marathon, which must be achieved by runners on or after Saturday, September 16, 2017; these qualifying times are based upon each athlete’s age on April 15, 2019, the date of the 2019 Boston Marathon.

Unfortunately, achieving one’s qualifying time does not guarantee entry into the Boston event, but simply offers the opportunity to submit for registration. In recent years, not all qualifiers who submit an entry have been accepted due to field size restrictions, and in such circumstances those who are the fastest among the pool of applicants in their age and gender group have been accepted.

From https://www.baa.org/races/boston-marathon/enter/qualify

Note: at the time of publication the Boston Marathon folks announced updated BQ standards for 2020, which effectively subtract 5 minutes from each of the age groups, making qualification that bit harder from 2020 onwards.

BQ Rates in Chicago

We define the BQ rate to be the proportion of runners in a given age group who achieve the BQ time associated with that group. In Figure 1(a) below we see the BQ rates for male and female runners, based on their individual ages. There is little difference between the BQ rates of men and women but, BQ rates tend to increase with age. For example, about 7% of runners in their 30s will secure a BQ, compared with more than 10% of runners in their 60s. Does this suggest that BQ qualification is tittled in favour of older runners or are we witnessing the benefit of experience, in the sense that older runners will, all other things being equal, tend to be more experienced runners?

Figure 1. BQ rates and ratios for male and female runners at the Chicago Marathon (2005–2017).

Notice the distinctive ‘saw-tooth’ pattern of the BQ rates in Figure 1(a), especially among older runners (>45 years old). This is indicative of systematically changing BQ rates within each BQ 5-year age group. For example, about 12% of 45 year-olds achieve their BQ time but over the next 4 years this rate falls to 9%, for the oldest members of this 45–49 age group. It’s a similar pattern for other age groups, and as runners age, qualification rates fall, and the difference between their group’s maximum and minimum BQ rates tends to increase. For example, 60 year-old runners achieve a BQ rate of just over 15%, dropping to 10% for 64 year-olds.

As a general rule (save for the unusually large 18–36 group) the best BQ rates are associated with the youngest runners in a group, and the worst BQ rates are associated with the group’s oldest runners. In fact, the difference between the best and worst BQ rates tell us about how increasing age effects performance.

In Figure 1(b) we present the ratio of the best-worst BQ rates for each age-group. For instance, for 55–59 year-old male and female runners, the BQ ratio if 1.4 and 1.5 respectively. This means that in this age-group, the best BQ rates (for 50 year-olds) are better than the worst BQ rates (for 54 year-olds) by a factor of 1.4 and 1.5 for men and women, respectively. In other words, each additional year reduces the BQ rate by about 5–10% depending on the age-group. For ‘younger’ runners in the 35–39 and 40–44 age-groups the effect is less significant than older age-groups; the effect is exagerated by for the 18–34 year-old age-group because of it’s much longer age-span (17 years) and probably also because of the influence of elites.

The BQ Margin

Focusing just on whether a runner achieves their BQ time is a rather binary matter. Two runners might achieve the BQ standard but one might do so with minutes to spare while another might just make it. Likewise, when a runner fails to achieve their BQ time, how much they miss by can be informative. We call this their BQ margin, which is simply the number of minutes by which they come in above or below their BQ time, as a fraction of this BQ time. For example, the qualification standard for a 50–54 year-old women is 4 hours (240 minutes). If such a runner achieves a time of 216 minutes then they will have come in 24 minutes below their BQ time and their BQ margin will be 0.1 (24/240); they have achieved their BQ time with a margin of 10%. If instead their finish-time was 252 minutes, then they will have missed their qualficiation time by 5 minutes, and their BQ margin will be 0.05 or 5%.

Figure 2. BQ margins for men and women who hit (a) and miss (a) their BQ standard.

Figures 2(a) and (b) show the BQ margins for runners who (a) hit and (b) miss their BQ times. In Figure 2(a) we can see that when runners achieve their BQ times, whether male or female, they tend to do so with a margin of 0.05–0.1, increasing somewhat for runners after their 50s. In other words, in Chicago, a greater proportion of older runners tend to achieve their BQ times and they tend to do so with more a margin. There is very little difference between men and women, except for among the youngest runners, where males enjoy the largest margins, perhaps because of a larger cohort of male elites.

In Figure 2(b) we see the corresponding margins for those runners who fail to secure their BQ times. This time the margin tends to decrease steadily with age. In other words, older runners tend to miss their BQ standard by an ever-decreasing margin, getting closer and closer to their qualification times. For example, unsuccessful 25 year-old males have a BQ margin of 0.44, meaning that, on average, they miss their 3 hour and 5 minutes standard by 44% (or 81 minutes). In contrast, a 60 year-old male runner in Chicago misses their 3 hour and 55 minute BQ time by just 26%, or just over 60 minutes. It’s a similar story for women except that they enjoy an even narrower BQ margin than their male counterparts. One way to interpret this is that runners who succesfully achieve their BQ times do so in a similar manner, whether male or female, but for runners who fail to achieve their BQ times, men tend to miss by a larger margin than women.

One explanation for this difference between men and women is the well-documented higher rate of hitting the wall among men, compared to women; runners who hit the wall rarely, if ever, achieve their BQ times and because many more men hit the wall than women we can expect their times to suffer accordingly. It is worth noting, but not shown, that even when we account for this — by excluding all runners who hit the wall from the analysis — women still continue to enjoy superior BQ margins to men, when they fail to meet their BQ standards.

It is also worth remarking how in Figure 2(b) we can see a similar saw-tooth pattern with BQ age-groups as the one we saw for BQ rates, back in Figure 1(a). Not surprisingly, as runners age within their age group, those who miss their BQ target tend to miss by a greater degree than younger runners within the same age group. A similar pattern is not evident, or at least far less clear, in Figure 2(a), for those who hit their BQ times, perhaps suggesting that minor differences in age has more of a bearing on less able runners (those who fail to BQ) than on more able runners (those who BQ).

Negative/Positive Splits and BQ Rates

How should one run in order to achieve a BQ time? Fast! Ok, let’s try that again. Is a runner more likely to achieve a BQ time by running a positive split (faster first half than second) or a negative split (faster second half than first), or does it matter?

To answer this question we split our Chicago runners, based on their halfway times, into those who run a positive split and those who run a negative split. In Figure 3(a) we can see how negative splits are fairly rare. Only 10–12% of younger runners run a negative split, this rate falls gradually with age; women are marginally more likely to run negative splits in Chicago, but the difference is not significant.

Figure 3. (a) Negative split rates for men and women; (b) BQ rates for men and women who run negative or positive spits.

What is significant, however, is the difference in BQ rates between positive and negative splits; see Figure 3(b). There is a clear advantage to running a negative split, regardless of gender or age. For example, only about 5% of younger runners (18–34 years old) who run a positive split go on to achieve their BQ time. In contrast, for the same age group, more than 10% of those who run a negative split achieve their BQ time. In other words, among 18–34 year olds, those running a negative split are up about twice as likely to achieve their BQ time, compared to those running a positive split. This negative split benefit persists across all of the age groups.

Pacing Strategy and BQ Rates

In our Chicago dataset we have access to the timings of runners at 5km (approx. 3.1 mile) intervals. This means we can calculate their pacing across each of the 5km segments from the start to the 24.9 mile mark, and from the 24.9 mile mark to the finish-line. Moreover, for each runner we can turn their actual segment paces (e.g. 8 mins/mile) into relative paces by dividing their actual pace for a segment by their average pace over the entire race. For example, if a runner runs the first segment at 7mins/mile and their average pace is 8 mins/mile then their relative pace for the first segment is 0.82, indicating that they ran it 12% faster than their average pace. We can use these relative segment paces as a pacing profile, to signal whether they ran a particular part of the race faster or slower than their average pace.

Figure 4. The pacing profiles (relative 5km paces) for runners who succeed or fail to achieve their BQ times.

Figure 4 shows the pacing profiles of runners for Chicago — (a) all runners, (b) males, (c) females — separating those who achieve their BQ times (BQ Success) from those who do not (BQ Failure). Each individual line corrsponds to a different age-group with the solid lines corresponding to the 18–34 year olds and the dashed lines to 65–70 year old runners; the paler, thinner lines correspond to each intermediate age group.

The main message to draw from these graphs is that the pacing profiles of those who achieve their BQ times are much less varied than those who do not. For example, in Figure 3(a), runners who achieve their BQ times tend to start the race 3–4% faster than their average pace (relative pace of approximately 0.93–0.94) and they tend to finish about 5–6% slower. By comparison, those runners who do not make their BQ times tend to start up to 10% faster and finish about 10% slower in their final 3.1 mile segment (before the ‘sprint’ finish). It’s a similar pattern for men and women, as shown in Figures 3(b & c).

It is also the case that, as Chicago runners age, their pacing profiles become more varied. Older runners, even those who achieve their BQ times, tend to start a little faster and finish a little slower than younger runners. The effect is slightly more exagerated for those who miss their BQ times and once again we see the same effect for men and women.

Pacing a BQ Attempt in Chicago?

How might all of this help someone to pace a BQ attempt in Chicago? Is there a set of recommended paces to run a successful BQ that is tailored for Chicago? In fact this is quite straightforward to determine, by calculating the average segment pacing of those who have (narrowly) achieved their BQ times in Chicago. In doing this we can produce a set of paces that reflect how runners BQ on the Chicago course, as opposed to using a simple one-size-fits all pacing model. In the tables that follow we present these paces for men and women, across the different age groups, for positive and negative splits.

As mentioned above, the Chicago race results are timed every 5 kms (3.1 miles) and so these pacing charts reflect pacing for each 5 km (or 3.1 mile) segment. In the tables below, we are use minutes per mile pacing, and the segments are labelled using miles; the corresponding tables for kms and mins/km pacing are included as an appendix at the end of this post.

To use these pacing tables simply find the table and row that corersponds your gender, preferred split type (positive or negative), and age group, and note the paces for each of the race segments. For example, for a 45–49 year old male, aiming to to make their BQ time (3 hours and 25 mins) with a positive split, then use the 45–49 row in Table 1. This recommends running the first 3.1 miles at 7m 29 per mile, then speeding up marginally over the next two segments before gradually slowing from the 9.3 mile mark to 7m 31s and then continuing to slow to finish in 8m 26s, which will get the runner over the finish-line in just under 3 hours and 24 minutes. For the same runner, if they wish to instead run a negative split then the recommended paces are in the corresponding row in Table 3, with female positive and negative splits in Tables 2 and 4.

Positive Splits

Table 1. Mins/mile BQ pacing for a male runner targetting a positive split.
Table 2. Mins/mile BQ pacing for a female runner targetting a positive split.

Negative Splits

Table 3. Mins/mile BQ pacing for a male runner targetting a negative split.
Table 4. Mins/mile BQ pacing for a female runner targetting a negative split.

One minor point worth making, for the sake of accuracy, is that in computing these average paces we have focused on those runners who narrowly achieve their BQ times, within a 1% margin. This ensures that the paces match a BQ time that is just within the qualification standard. Had we included all BQ qualfiiers then we would have produced pacing tables with more ambitious times, which are probably less useful, and certainly more risky, for most runners. In any event, if a runner wishes to target a more ambitious BQ time then they can always borrow the pacing from a younger age group.

Conclusions

Running a BQ is far from straightforward and most don’t manage it. Those who do, achieve it by pacing themselves carefully — without starting too quickly to avoid finishing too slow — and there is some evidence that a negative split may increase the likelihood of securing a BQ time. The BQ pacing tables above provide concrete pacing recommendations to achieve a BQ time that is tailored for Chicago. If they help you please let me know!

Appendix — Kilometer Pacing

The following tables have been converted to metic, using kms and mins/kms pacing. They can be used in the same way, and target the same BQ times, as the pacing tables above.

Positive Splits

Table 5. Mins/km BQ pacing for a male runner targetting a positive split.
Table 6. Mins/km BQ pacing for a female runner targetting a positive split.

Negative Splits

Table 7. Mins/km BQ pacing for a male runner targetting a negative split.
Table 8. Mins/km BQ pacing for a female runner targetting a negative split.