Running hurts. It hurts more at mile twenty. There is a specific moment in a marathon when everything falls apart. Runners call it “hitting the wall.” Or just “bonking.” The body runs out of glycogen. Those stored carbohydrates vanish. Fatigue hits hard. Pace drops. It’s unpleasant.
New research suggests men do this twice as often as women.
The data is heavy. Eight hundred thousand runners. The Berlin Marathon from 1995 to 2025. A lot of pavement. The study appeared in Scientific Reports recently. Researchers defined bonking mathematically. If you run the second half 20 percent slower than the first you bonked. Positive splitting. A confession of bad strategy.
The results were stark. Men were twice as likely to collapse. Not just a little bit. Twice as much. And the faster the men ran the worse it got. A guy under three hours? Six times more likely to fail than a similarly fast woman. Three hours is fast for Boston qualifier speed for men. It is not fast for women.
This surprised the researchers. Aldo Seffrin from Brazil co-authored the paper. He expected experience to help. He thought elite male runners would have learned pacing by now.
“I expected experience and training to flatten the differential,” Seffrin said. It did not.
Glycogen is fuel. When it goes away the body switches to fat. Burning fat is slow. It’s messy. It requires oxygen and patience. Running requires speed. The two don’t mix well. A steady pace saves glycogen. Negative splitting does too. That means running slower first. Then faster later. Men rarely do it. They fly out the gun.
Pacing failure is not simply a beginner’s mistake.
But pacing isn’t the only thing. Biology plays a role. Women burn fat better. They have a lower respiratory exchange ratio. Simple translation. Women are more efficient at using fat as energy during steady exercise.
Then there are muscle fibers. Women have more type 1 fibers. Slow-twitch. Built for endurance. Resistant to fatigue. Estradiol helps. The hormone preserves carbohydrates. It manages energy better than testosterone in this specific context. Maybe. We don’t know enough yet.
Historical data favors men. Exercise physiology was built on men. Female physiology was an afterthought. We have guesses. We need facts. The performance gap shrinks in ultramarathons. Longer distances. Less explosive power. More endurance. Women pull even.
Why do men bonk? It’s a mix of hubris and biology. Or maybe just biology wearing the mask of bad pacing. Who knows. The dataset was huge but the understanding remains shallow.
More research is needed. Especially on women. We can stop assuming male patterns are the default.
Better characterization of female-specific physiology is what would let us move to why.
The wall is still there. It waits at mile 20. Or maybe 21. It depends on your strategy. It depends on your body. The data doesn’t fix the pain. It just explains the drop.
Some will ignore the data. Some will keep flying out of the start. That’s their choice. The pavement doesn’t care about gender. It only cares about time.
You hit the wall when you decide you have unlimited energy.
Spoiler alert. You don’t.
