Male marathon runners might be twice as likely to “hit the wall” as women – the reason might surprise you.

Run a marathon it’s hard work; the miles don’t get easier as they go by. Among a runner’s worst fears is a phenomenon known as “hitting the wall” or “bonking,” which occurs when the body’s glycogen stores become depleted. This leaves the runner feeling crushing fatigue, exhaustion, and an inability to keep up. But new research this week suggests that men may be much more likely to get upset than women.

In a study published Thursday in Scientific reportsscientists wanted to better understand which marathon runners might be most prone to hit the wall and when. They looked at the race times of 873,334 runners who completed the Berlin Marathon between 1995 and 2025. They determined that a runner had hit the wall if their pace slowed by at least 20% during the second half of the race compared to the first half. This is known among runners as positive split, where the first half of the race goes faster than the second half.

Male runners were about twice as likely as females runners hit the wall, according to the data. The researchers also found that faster male runners were even more likely to get angry. Male runners who finished the marathon in less than three hours — which was the men’s qualifying time for the Boston Marathon and well below the women’s qualifying time — were six times more likely to hit the wall than their fast female counterparts.

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This is the most surprising finding, says study co-author Aldo Seffrin, an exercise physiologist at Nova O2 Sports Science in São José dos Campos, Brazil. “I expected that experience and training would reduce the gap at the top, but instead it has widened,” he says. “This tells me that failure is not just a beginner’s mistake.”

The main cause of bonking is the depletion of glycogen, which is the body’s stored form of glucose and its preferred fuel for fueling muscles. Once glycogen reaches a critical level, the body relies on fat for energy. But converting fat into a usable form of fuel is neither a quick nor easy process.

In fact, scientists are still piecing together what leads a runner to get upset. But a good pacing strategy plays a key role. Moving at a steady, sustainable pace allows the body to use energy (primarily in the form of glucose from glycogen stores) more efficiently, reducing the risk of using up all stored glucose before the finish line. Seffrin and his team note that their study suggests that men might be able to counteract the splurges by running slower in the first half of a marathon and continually getting faster as the race progresses, a pacing strategy known as negative splitting.

But pace alone may not fully explain why women are less likely to hit the wall than men. “The honest answer is that much of the fundamental physiology of exercise was built on male subjects, so many mechanisms are simply less well characterized in women,” says Seffrin.

Researchers know that “women tend to oxidize fat at a higher rate and run with a lower respiratory exchange rate during submaximal endurance exercise,” he says. In other words, women tend to burn more fat for energy than men during regular, moderate-intensity endurance exercise, like a marathon.

Women also have a greater relative proportion of type 1 muscle fibers, also called slow-twitch muscle fibers, than men. These use oxygen efficiently to resist fatigue, making them ideal for endurance exercise. And they also use the hormone estradiol which plays a role in fat burning and carbohydrate storage during prolonged exercise.

All this could also explain why the performance gap between men and women in ultramarathons is often smaller. However, more research on women’s bodies is definitely needed. “Better characterization of female-specific physiology, in data sets that actually include it, is what would allow us to move from the ‘what’ to the ‘why’,” says Seffrin.

In the future, Seffrin says his team hopes to combine running data with other information about each runner, including psychological and physiological factors. This would help determine whether differences in pace and wall striking are primarily due to running strategy or biology. And they want to study runners who don’t finish, because analyzing only finishers probably underestimates how often runners actually binge.