How much of the post-2017 marathon speed-up is the shoe?
73seconds
95% CI −4 to 150 s · about 1.0% of a 2:05 marathon
Three separate methods estimate how much carbon-plated shoes took off median elite
marathon time between 2010–2016 and 2018–2024. They land between 44 and 199 seconds,
and pooled they come to a little over a minute, about 1.0% of race time. The treadmill study behind the
Vaporfly’s name measured a 4% cut in running energy cost, not in race time
(Hoogkamer et al. 2018).
Updated 28 October 2026: wheelchair and handcycle results that the scraper had read as running times are now excluded. The pooled figure was 67 s before.
28 October 2026: the bootstrap now resamples the same statistic as the estimate. The pooled figure was 82 s [6, 159] before that fix.
Shoe contribution by framework, seconds, with 95% intervals
Difference-in-differencesroad marathon vs track 10,000 m, women-only pre-era
199 s[83, 338]
Within-athlete paired16 athletes in both eras, p = 0.39
44 s[−62, 121]
Cohort survival55% of the top-30 shift, break at 2020
71 s[58, 98]
Pooledweighted by inverse squared CI width
73 s[−4, 150]
−50050100150200250300
Values from outputs/analysis_summary.json.
Three ways to hold the rest constant
The shoe arrived alongside better pacing, deeper East African fields and faster courses, so a plain
before-and-after comparison credits the shoe with all of it. Each framework strips out a different part of that.
Difference-in-differences. Road marathon improvement minus track 10,000 m improvement over the
same window, rescaled to marathon time. Anything that lifted both events cancels.
Within-athlete paired. The same runner’s career-mean time before and after 2017, which holds
genetics and training history fixed. Not age-adjusted, because the race tables carry no ages.
Cohort survival. The shift in the top-30 median between eras, with 55% attributed to shoes,
plus a changepoint search on sub-2:10 and sub-2:25 counts.
Other numbers from the run
2.6% / 0.3%
Women’s road marathon top-50 median improved 228 s (2.57%); track 10,000 m improved 0.32%.
1.25–2.0×
Rise in sub-2:10 (men) and sub-2:25 (women) performances per year after 2017, in six major marathons.
2020
Changepoint in the sub-threshold counts, three years after the Vaporfly’s commercial release.
10 of 16
Paired athletes who were faster in the post-Vaporfly era. Median change: 44 s faster.