Risk vs. Reward: Pacing conundrum for Boston Marathon & endurance events generally

At this point in the training cycle, within a week of my first big race of 2017, I have as clear an understanding of my  current fitness as I will get. While the taper does include some workouts, they are less telling than near-max efforts weeks and months ago.

So this is an appropriate point to settle on a final goal time and a pacing strategy. I’ve been pondering the subject all week — the answers do not come easily.


The challenge is this: How can I accurately extrapolate my training data to a specific race and to specific race day conditions?

Ideally, I would have a vast and relevant dataset. For example, if I’d finished the Boston Marathon multiple times, seen a wide range of race day weather, and followed the same training regimen for years, my finish time would be predictable and my pacing strategy would be well informed.

But I’m working with much less data. I have:

  • Not raced Boston.
  • Completed only one other marathon, the Colorado Marathon, but that course is dramatically different and my fitness has dramatically improved since then.
  • Seventeen percent less oxygen in Boulder, Colo. than in Boston, Mass.
  • No training routes that match perfectly Boston’s vertical profile. And,
  • Not done the same workouts so many times that I know precisely how changes in temperatures, wind, and sun exposure affect my performance.

In this case, input from a coach and/or race veterans is extremely useful. By sizing up my workouts and past performances against those of other runners, I can narrow the range of possibilities, in my case to within about a 4-minute window. Still, four minutes is huge:

  • A 2:29-high is more impressive than a 2:33-high, but more importantly,
  • Attempting to run a 2:30 if you’re in 2:34 shape, or a 2:34 if you’re in 2:30 shape, will not result in a peak performance.

Pacing: Risk versus reward

The optimal pacing strategy for a marathon depends on the runner and the course, but generally it involves even or slightly positive splits. If my goal time is spot-on and if I follow the racing plan, the last few miles should really suck, but I’ll roughly maintain my pace through the finish line.

If I start more aggressively than what I believe to be my optimal pace, I may surprise everyone with a huge PR (in which case my goal time proved to be too conservative), or I may blow up and slow down dramatically.

A training partner swings for a new PR but struggles to bring it home, losing significant time in the final miles.

If I start more slowly than what I believe to be my optimal pace, I can’t offset all the time I “lost” early on, but the race won’t be an epic fail either because I won’t be relegated to a jog or even a walk for the final 10k (unless my goal time was way too ambitious, in which case it’ll be a great thing that I started as conservatively as I did).

My pace at last year’s Colorado Marathon steadily increased, but not enough to offset the “lost” time from an overly conservative start.

Besides finishing time and place, there is an emotional aspect to how a race ends. If I run conservatively and leave some on the table, I remain hungry for the next race, wanting to prove I can do ever better. If I put it all on the line, motivation to return to the well again may be lacking for some time.

Boston predictions

To help illustrate this conundrum, here are coach David’s predictions for my Boston finish:

I think the range of times in a normal weather year is:

  • 2:31 to 2:34, if you go out at 2:33 pace;
  • 2:29 to 2:39, if you go out at 2:30 pace; and,
  • 2:28 to 2:42, if you go out at 2:29 pace.

So around here this week, the two big questions are:

1. How accurate is David’s sense for my fitness? (I’m inclined to believe him — he’s been pretty good so far.) And,

2. On Monday am I going to swing for a homerun (and risk a strikeout) or try for a humble double (and settle for a single if I don’t get the exact pitch I want)? If you know me at all, you probably know what I’m currently thinking.

Posted in on April 11, 2017


  1. Rob W on April 12, 2017 at 7:43 am

    So how’s the weather looking for Patriot’s Day?

    Knock it out of the park!

    • Andrew Skurka on April 12, 2017 at 8:03 am

      Looking great right now. 60 degrees (a bit warm, but manageable) and a 15 mph tailwind!

  2. Dave M on April 12, 2017 at 9:56 am

    Hi Andrew, I’ll be running Boston as well (although I’ll be happy to crack 3:00 as goal). Can you comment or write a post on what your strategy/thoughts are on pre-race nutrition (e.g. carb loading) and nutrition during the race? Do you plan to carry a small bottle or light weight fuel belt with goo packs?

  3. IT on April 12, 2017 at 12:18 pm

    Go big or go home

  4. Will T. on April 12, 2017 at 1:13 pm

    All that extra oxygen, a tail wind, and downhill for the first 15k, seems counterintuitive to hit the brakes out of the gate and have to pick up the pace later in the race on the climbs. Seems you could take advantage of the first 15k without doing much damage so you don’t have to push as hard through the climbs in the middle, then have some energy left in the tank to keep the wheels spinning on the final 5 mile descent to the finish. If 2:29:59 was my goal, I would try to come through the 1/2 in 1:13:30-45, so you can give some time back on the hills. Best of luck. Looking forward to your recap article.

  5. Jeff Valliere on April 12, 2017 at 3:27 pm

    I think you will run smart, yet swing for that homer. Until the old guy blasts by with the Stars and Bars split shorts, then all bets are off…. 😉 Wishing you the best out there, I’ll be following close on race day, then dragging you back up those hills on Wednesday.

  6. Brian on April 12, 2017 at 3:53 pm

    So tough. I like the way David lays things out, and like you, I’m inclined to believe him.

    I’m a data rationalist, but also an optimist. I think I would personally split the difference in the first two options. Go out 2:31-32 pace.

    Can’t wait for more thoughts and updates, and of course, Marathon Monday.

  7. J Scott Wharton on April 16, 2017 at 4:49 pm

    Pick your run passion and enjoy after all it is the Boston Marathon. Look forward to the after run analysis.

  8. Rob M on April 16, 2017 at 6:58 pm

    Wishing you the best of luck tomorrow!

  9. David on April 17, 2017 at 1:09 pm

    2:32! Nice job today!

  10. Jim Dean on April 17, 2017 at 2:54 pm

    Congrats on a great race! Way to go!

  11. Mira on April 19, 2017 at 7:35 am

    Congrats on a great time!

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