The wall is common; fast starts raise the risk
Medium confidence
Across more than 4 million race records, 28% of men and 17% of women with more than one race hit the wall. That meant slowing at least 25% below their own 5 to 20 km pace for 5 km or more after 20 km. Rates rose among slower runners and in the 1 to 3 years before a runner's fastest time. In data from over 25,000 runners, those who ran 2 to 16 km faster than 94% of critical speed slowed sharply late more often. The share rose from 21% to 26% in men; in women the rise, from 10% to 16%, was not statistically clear. In a survey of 82 marathoners, those with more marathons behind them paced slightly more evenly, though finish time and personal bests were the strongest links.
Why it works
Critical speed is the fastest pace your body can hold in a physiological steady state. Running the early miles close to it may leave less in reserve for the late miles, but these studies did not test why runners slowed.
What it means in practice
Encourage even pacing from the start and present the wall as common, especially for men and slower runners. Frame these as patterns in race records, not proof that even pacing prevents the wall.
The evidence
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Hitting the wall was defined as running at least 25% slower than your own 5-20 km pace for at least 5 km after the 20 km mark. Among repeat runners, 28% of men and 17% of women hit the wall, and rates rose steadily with slower recent personal bests while age mattered little. In the 1-3 years before their fastest recorded time, 40% of men hit the wall versus about 26% in the 4-9 years before, and 28% of women versus 16%. The data are observational race records, so they show patterns, not causes.
n=4183362
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Using raw training and race data from more than 25,000 recreational marathon runners, the authors showed that critical speed (the fastest pace a runner can hold in a physiological steady state) can be estimated straight from everyday GPS data. The best model, built from 400 m, 800 m, and 5,000 m efforts, predicted marathon finish time with about 7.67% error. Runners raced the marathon at roughly 84.8% of critical speed on average, with faster runners holding about 93% and slower runners about 78.9%. Runners averaged about 87.6% of critical speed early in the race, and those who ran the first half above about 94% of critical speed (particularly faster than it) were more likely to slow by more than 25% in the second half.
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Runners who had run more marathons paced their races more evenly, and so did those who trained with longer runs. The strongest correlates of pacing were finishing time and race personal bests, with experience and training measures weaker but significant. This is a cross-sectional survey (139 respondents, 82 even-pacing runners analysed), so it shows correlation rather than cause. Prior race exposure tracks with pacing skill. It does not show that tune-up races build it.
n=139
Why we call confidence medium
Two large datasets agree that the wall is common and more common in men. Only one, Smyth 2020, ties a fast early pace to late slowing, and the effect was modest. All of it is observational, so it shows associations, not proof that even pacing prevents the wall.
Where it applies
Recreational marathon runners.
Does not apply to: elite marathoners; claims that even pacing alone prevents the wall; fueling effects on the wall, which these studies did not measure.
Last reviewed Nov 1, 2026. See how we score.