The Marathon Autopsy™
Post-race diagnostic · second and third attempts

You missed by minutes.
Find out why.

Six failure modes tested against your own splits, heart rate, weather, and training block. One named cause. The rest ruled out, with your numbers. Exactly two changes for the next block.

Get the Autopsy $27

Instant download · 60-day no-questions refund · Excel workbook, km and miles editions · science PDF · three bonuses

Verdict · goal 3:00:00 · finished 3:02:55
Under-fuelling
High confidence · 90 / 100 · pacing contributed (70), thermal ruled out (0)
Aerobic ceiling
15
Under-fuelling
90
Thermal
0
Pacing
70
Race-pace work
37
Taper / freshness
0
40 g/h against a 75 g/h plan. Last 8 km 5.5% slower than 25 to 35 km. Heart rate did not lead the fade. This is the worked example shipped inside the workbook.
The problem

A slow second half has at least four causes

Too hot. Went out too fast. Should have taken more gels. Needed more long runs. Every answer plausible, none checked against your splits. So you change three things at once and sixteen weeks later you still cannot say what worked.

1

Enter the race

Goal, finish, cumulative clock at every 5 km or 3 miles, heart rate if you have it, the weather, twelve weeks of volume, your fuelling, three yes/no flags. One yellow tab.

2

Read the verdict

Each of six failure modes is scored against its own fingerprint in your data. The top score is the cause. The others are ruled out in writing, with the number that rules them out.

3

Change two things

Exactly two changes for the next block, what to leave alone, whether the goal was ever inside your fitness, and whether to run the same race again.

Six fingerprints

Each cause leaves a different mark

A fuelling failure and a pacing failure both give you a positive split. They do not start in the same place, they do not have the same shape, and heart rate does not behave the same way before the fade.

1

Aerobic ceiling

Goal beyond what the recent half predicts; a linear slide from 25 km; heart rate high but steady.

2

Under-fuelling

Intake under 60 g/h or far below plan; the last 8 km collapse; a step change late; heart rate does not lead.

3

Thermal

Heat index explains most of the shortfall; heart rate climbs before pace falls; progressive fade from early on.

4

Pacing

First 10 km clearly faster than goal; ahead at halfway; fade before 30 km; conditions benign.

5

Race-pace work

Marathon-pace share of volume thin; few runs over 30 km; fade in the classic 25 to 35 km window.

6

Taper or freshness

Race-week reduction outside 35 to 75%; illness, travel, or broken sleep; slow from the gun.

What you get

The workbook, the science, and three bonuses

Failure modes
6
Discriminators
28
Live formulas
817
Changes prescribed
2

The Marathon Autopsy workbook

Fourteen tabs, one of which you type in. Dashboard, Verdict page, Scenario Planner with conservative, realistic, and best-case projections, a 16-week next-block skeleton shaped by the verdict, split analytics, and every threshold visible and editable. Km and miles editions. Opens in Excel, Numbers, or Google Sheets. No login, no macros.

The science behind it

A 12-page PDF, one section per page, explaining each fingerprint and the research it rests on: Riegel, Ely, Coyle, Jeukendrup, Bosquet, and others. Written so you can argue with it.

Bonus 1

Strava and Garmin data prompts

Eight copy-paste prompts for Claude or ChatGPT with a connected Strava or Garmin account. They pull your splits, segment heart rate, weather, twelve weeks of volume, marathon-pace kilometres, and your best recent half, keyed to the workbook's cells. Ten minutes instead of an evening.

Bonus 2

Weekly on-track review

A prompt you set as a Monday routine for the next block. It reads the week from Strava or Garmin and returns one of four verdicts: on track, at risk, off track, or rethink the goal. Then two adjustments, never more.

Bonus 3

Race Week Checklist workbook

A seven-day countdown, a race-morning timeline computed from your start time, kit and bag-check lists, a heat-adjusted pace card with gels aligned to aid stations, and a printable one-pager. Same heat table as the Autopsy, so the two agree.

Get the Autopsy $27
Who it is for

Missed by under ten minutes, with the splits to prove it

  • Second or third attempt at a marathon goal
  • A GPS watch with 5 km or mile splits from the race
  • Already paid for the plan, the entry, the travel, and the shoes
  • Wants a cause, not a menu, before the next block starts
Who it is not for

It is not a training plan

  • First marathons
  • Misses of more than fifteen minutes, where the cause is rarely subtle
  • Anyone without split data; the engine needs the 5 km clock readings
  • Anyone looking for a plan to follow; this tells you what to change in yours
From the author

I built this after missing the same goal twice

I am Pedro. Nine marathons since 2022, from 3:48 to 2:52. On paper that is a good progression. In practice it includes a DNF, a Boston seven minutes slower than the Chicago before it, and two races fast enough to be personal bests that still missed the goal I had trained sixteen weeks for.

Each time, the forum answer was a menu. Heat, pacing, gels, mileage. I picked one, changed three things, and the next block was a new experiment with no control. I wrote the Autopsy so the answer would be derived from my own splits rather than voted on by strangers. This is the tool I wanted at 3:06 in Boston, and the one I used before Valencia.

If you know the feeling of a sixteen-week block ending in a miss you cannot explain, this was written for you.

Finish times, 2022 to 2026
Red marks are goals I trained for and missed. The dashed line is 3:00.
Marathon Date Time Pace Note
Brighton April 2022 3:48:27 5:25 /km
Lisbon October 2022 DNF Did not finish
Aveiro April 2023 3:28:11 4:56 /km
Berlin September 2023 3:13:50 4:36 /km
London April 2024 3:00:32 4:17 /km Qualified for Boston
Chicago October 2024 2:58:52 4:12 /km New York qualifier: missed
Boston April 2025 3:06:00 4:23 /km Seven minutes slower than Chicago
Valencia December 2025 2:52:47 4:05 /km Personal best · New York qualifier: missed
Boston April 2026 2:55:19 4:08 /km
Objections

The questions people ask before buying

Then the workbook agrees with you in ten minutes and you have the evidence instead of the feeling. If it disagrees, that is what you paid for.
It does not need to be. Splits alone separate pacing from fuelling. Heart rate adds thermal. A recent half tests the goal. The Dashboard reports how many of the six modes were fully tested, and a low-confidence verdict names the one piece of data that would settle it.
Yes. 817 formulas, no macros, no login, no model that changes under you. It opens in Excel, Numbers, or Google Sheets and it will still open in five years.
Ask one. Bring the Verdict page; it is the conversation a good coach wants to have and the one a forum cannot.
Sixty days, no questions. Reply to your receipt email and the full amount is refunded. You keep the files.
Guarantee

Sixty days. No questions.

Run the Autopsy, read the verdict, take it into the next block. If at any point in the first 60 days you decide it was not worth it, reply to your receipt email and the full amount is refunded. No reason needed, no form, and you keep the files.

Stop relitigating the race

One cause. Two changes. A decision.

Both workbook editions, the science PDF, the data prompts, the weekly review, and the Race Week Checklist. Instant download.

Get the Autopsy $27
60-day no-questions refund · Excel, Numbers, Google Sheets · km and miles