Male marathon runners are twice as likely to “hit the wall” compared to female runners, according to a study of 873,334 race finishes published in Scientific Reports. The research, which analyzed data from the Berlin Marathon between 1995 and 2025, defines this phenomenon—also known as bonking—as a pace reduction of at least 20 percent in the second half of a race.
Why do marathoners “hit the wall”?
Hitting the wall occurs when the body depletes its glycogen stores, forcing muscles to transition from using glucose to burning fat for energy. Because the conversion of fat into fuel is a slower, less efficient process, runners experience sudden, overwhelming fatigue and a sharp decline in pace. According to Aldo Seffrin, an exercise physiologist at Nova O2 Sports Science, maintaining a steady, sustainable pace is vital to preserving glycogen levels until the finish line.
The phenomenon of “positive splitting”—where a runner completes the first half of a race significantly faster than the second—is a primary indicator that an athlete has bonked during a marathon.
How does biological sex impact endurance performance?
The study found that the physiological gap between male and female runners actually widens among elite performers. Men who finished in under three hours were six times more likely to hit the wall than female counterparts with similar finishing times. Seffrin notes that this indicates pacing failure is not merely a byproduct of inexperience, as one might expect from beginner runners.
Several biological factors may grant women a physiological advantage in endurance events:
- Fat Oxidation: Women tend to oxidize fat at higher rates during submaximal exercise, sparing precious glycogen stores.
- Muscle Fiber Composition: Females generally possess a higher proportion of type 1 (slow-twitch) muscle fibers, which are highly resistant to fatigue.
- Hormonal Influence: The hormone estradiol plays a role in conserving carbohydrates during prolonged physical exertion.
What can runners do to prevent bonking?
While biological differences play a significant role, race strategy remains a critical tool for all athletes. Researchers suggest that runners, particularly men, could reduce the risk of glycogen depletion by employing a “negative split” strategy. This involves running the first half of the marathon at a conservative pace, allowing for a faster, more controlled second half.
If you find yourself slowing down significantly after the 20-mile mark, try adjusting your training to include longer, slower endurance runs that emphasize fat-burning efficiency rather than pure speed.
Future research on endurance limits
Current sports science is limited by the fact that much of the foundational exercise physiology research was conducted using male subjects. Future studies aim to bridge this knowledge gap by incorporating psychological factors and wider datasets. Seffrin and his team at Nova O2 Sports Science intend to analyze runners who do not finish, noting that current data likely underestimates the true frequency of bonking because it only accounts for those who cross the finish line.
Frequently Asked Questions
What does it mean to “hit the wall” in a marathon?
It is a state of severe exhaustion caused by the depletion of the body’s glycogen stores, typically occurring during the latter stages of a long-distance race.
Are women naturally better at pacing than men?
Data suggests women are significantly less likely to experience a 20 percent drop in pace during the second half of a marathon, likely due to metabolic differences in fat oxidation and muscle fiber types.
Is bonking just for beginners?
No. According to the Scientific Reports study, faster male runners are actually more prone to hitting the wall than their slower counterparts, suggesting that high-intensity pacing can trigger the phenomenon regardless of experience level.
Have you ever hit the wall during a long-distance run, or do you have a specific pacing strategy that works for you? Share your experiences in the comments below, or subscribe to our newsletter for more insights into the science of endurance sports.