Published on July 20, 2026 at 06:00 AM
In 1992, two physiologists published paper In the prestigious magazine nature Expect that the gap between men’s and women’s running performance will continue to narrow and eventually disappear completely. They predicted that women would make the fastest progress in the longer events: Based on past trends, the best male and female runners would be equal in… 1998.
It didn’t happen. There now Great evidence Sex differences in physiology give male athletes insurmountable advantages in strength, speed, and endurance over their female counterparts in the most common sporting events. But the idea that women might have a comparative advantage over really long distances persists. This resurfaces every time an exceptional female athlete outperforms her male competitors, such as ultra-runner Rachel Entrekin. I did recently At the 250-mile Cocodonna Race in Arizona, a phenomenon that seems to be happening more and more repeatedly.
Why women might have an advantage
Many theories have been put forward as to why women do better — or at least narrow the gap — over long distances. It may be physiological: For example, they tend to burn more fat and fewer carbohydrates than men, making them less likely to run out of fuel prematurely. They also have a greater proportion of slow-twitch muscle fibers rather than fast-twitch muscle fibers, which are more resistant to fatigue. Or it could be psychological: the longer the race, the less physiology matters and the more mental toughness matters, which at least levels the playing field, or perhaps even gives women an advantage.
now, New paper in Scandinavian Journal of Medicine and Science in Sports He offers another possibility: Maybe women have it better Fatigue resistance Of men.
Fatigue resistance is a relatively new idea that has emerged as one of the hottest topics in endurance science over the past five years or so. The traditional view is that you can predict a runner’s endurance performance by heading to the lab and measuring his strength VO2 max, Current economyand Lactate threshold. But these tests are done when the runner is fresh. If you test them again after an hour or two of running, all three things will get worse. The change is much greater for some runners than for others. A growing body of evidence suggests that one of the keys to outstanding endurance performance is to have good resistance to fatigue, i.e. not only having a high VO2 max etc. in the laboratory, but also save Them high as you get tired.
There are two sub-components of fatigue resistance. “Physiological flexibility” refers to how much your basic organ functions — things like VO2 max — change with fatigue. “Durability” refers to how much your actual performance capacity changes: how quickly you can run a mile when you’re fresh versus after a few hours of running, for example. Scientists are still trying to figure out exactly how the two traits are related.
What the new study shows
Researchers at the University of Innsbruck in Austria recruited 11 female and 11 runners, all experienced and highly trained. The groups were carefully selected so that they had similar performance levels for their gender, i.e. men were faster on average than women, but they tended to place at a similar level in their racial divisions. This is a rather difficult point and we will return to it.
The main performance test consisted of three sets of 60-minute runs at a predetermined moderate intensity, followed by a 12-minute all-out climb trial at a 12 percent grade, for a total running time of 3 hours and 36 minutes. Throughout the operation, a series of measurements are performed: oxygen consumption, lactate levels, biomechanical analysis, and more. The goal was to find out how these various factors changed over time, and whether there were any differences between men and women.
There are a whole host of results to look at, but the most important is also the simplest: how quickly were runners able to sprint through three grueling 12-minute trials, compared to when they did the same test in a state of non-fatigue? Below is the data, showing percentage deceleration after one, two, or three hours of moderate running, with females in red and males in blue:
The differences here are very stark. Women show much better durability: they barely slow down at all in the grueling time trials, while men get progressively slower. In the final experiment, the men were ten percent slower on average, while the women were only one percent slower.
It is not clear why women perform so much better – or, to use scientific terminology, what aspects of physiological flexibility enable superior durability. Maximum leg strength tests decreased by 18% in men but did not change in women, which is consistent with previous research that showed less muscle fatigue in women. Carbohydrate burning decreased sharply in men compared to a more moderate decrease in women. There were also differences in heart rate and perceived effort.
Apples to apples problem
The simplest explanation for all this data is that women are “better” at burning fat than men, perhaps in part because they rely more on slow-twitch muscles. This means they rely less on carbohydrates, which means their muscles are not depleted, which means they are able to maintain their fatigue-free performance levels for longer.
In support of this view, here is the data showing carbohydrate burning (“CHO oxidation”) over the course of three hours of moderate running, with men in blue and women in red:
Men actually start out with much higher levels of carbohydrate burning, but they steadily decline, while women are able to maintain roughly the same levels throughout.
But there is an unanswered question here because of the way the two groups are compared. Moderate running pace has been linked to just below the lactate threshold. But if men and women were different, perhaps an arbitrary percentage of the lactate threshold would lead to different responses. For example, here are the ratings of perceived exertion (RPE) for the two groups:
From the beginning, the men realized that running speed was becoming more difficult, and then the gap widened as the running progressed. But what would have happened if they had started a similar effort? Or at a pace that elicited similar levels of carbohydrate and fat burning?
In practice, it is impossible to make a true apples-to-apples comparison when comparing apples-to-oranges. Perhaps most important, for equal amounts of time spent running, men ran farther, covering a total of 26.5 miles compared to 22.1 miles for women. If the cumulative effect of hitting the feet on the ground is part of what causes muscle fatigue, it’s perhaps not surprising that men show a greater decline. But if you run the experiment over equal distances, women will end up running longer. There is no perfect solution.
Despite these caveats, the observed sex differences in fatigue resistance are interesting, and fit with the idea that female physiology is well suited to long distances. But personally, if I had to guess why runners like Entrekin, Courtney Dawalter, and Jasmine Paris have had such amazing performances in recent years, I wouldn’t attribute it to this quirk of their physiology. In general, I found studies It is very difficult to predict the success of ultrasonic operation based on laboratory tests. Every race at every distance tests the body and mind, but the balance shifts toward the latter as the distance increases. If traits like mental toughness are so amorphous and difficult to measure in the laboratory, that it’s dangerous to jump to premature conclusions about who “should” win a super prize — well, I’d call that a feature of the sport, not a bug.
For more race science, sign up Email Newsletter And check out my new book The Explorer Gene: Why we seek great challenges, new flavors, and empty spots on the map.
