Rachel Entrekin & the Reality of Extreme Capacity
Imagine racing 250 miles (402.3KM) through an Arizonan desert. The heat, dust and mountains make up the course of the Cocodona 250, an ultramarathon challenge that obliterates even the strongest amongst us. But not Rachel Entrekin, the winner of this year’s race. She finished in 56 hours, six minutes and 48 seconds, six hours faster than her 2025 effort, and a full two hours and 38 minutes faster than the men’s course record.
Reading the story of her victory is the stuff of nightmares. “A key part of Entrekin’s race plan… was taking strategic ‘dirt naps’. [She] took three of them for a total of 19 minutes of sleep over almost two-and-a-half days of racing.” We talk a lot about adaptive capacity – it’s what ZAAG’s designed to enhance – and to function at that level with so little sleep couldn’t underscore a greater example of somebody whose capacity is truly astonishing.
The physicality of a 400KM race is self-evident. Blisters, cramps and stomach issues are a given for almost anyone running for this long. That said, the mental strength required, coupled with intense sleep deprivation, requires a whole different calibre of person over someone who’s just in shape.
The body and mind get absolutely battered in these events, as we’ve discussed at length. Entrekin has said she doesn’t often get hallucinations, a common occurrence for ultra runners, but at Cocodona she did, seeing a “shape-shifting bird”. This speaks to the depth of grit required to complete a task like this – particularly in such a startling time.
Rachel’s achievement joins the canon of remarkable female victories, like Maggie Guterl’s 2019 win at Big Dog’s Backyard Ultra and Courtney Dauwalter’s legendary 2017 victory at the Moab 240, where she beat her nearest competitor by ten hours. These individual feats celebrate the incredible resilience of women and have sparked a global debate: does the data truly support the idea that women outrun men as distances become extreme?
The Data: Reality vs. Statistical Mirage
Since Entrekin’s win, we’ve seen numerous citations of a 2020 analysis of over 5,000,000 data points from 15,451 events that marketed the claim that “above 195 miles, women are actually 0.6% faster than men.” They stated that as the race distance increases the "gender pace gap" significantly narrows—from 17.9% in a 5K to just 0.25% in a 100-miler.
This 2020 study builds on earlier research from the 90s that demonstrated the rapid uptick in the speed of women running. Nature magazine, in ‘92, carried a letter from two physiologists predicting that women would catch and surpass men in the marathon by 1998.
The ‘90s research didn’t account for recency bias. Women’s long-distance running was stigmatised across the world until the 1980s – the women’s Olympic marathon was only introduced in 1984. As a result, women got a lot better at running in a very short period of time, but that hockey stick improvement couldn’t continue as a trend. The physiology doesn’t make sense.
Data visualised by Reddit user ‘dhaitz’ from Wikipedia records, far from perfect, but illustrates the point.
With regards to the 2020 analysis that claims women ran distances over 195 miles faster than men, many performance experts argue the conclusion is largely a statistical illusion caused by participation bias. That is to say, far fewer women run extreme ultramarathon distances compared to men, as demonstrated by the below graph from the report itself.
This smaller pool (16%, almost certainly lower) of women often consists of highly prepared, better trained athletes, compared to the larger pool (84%) of male participants, which includes a far broader range of less prepared and trained runners, lowering the male average overall. This is why the numbers show up the way they do.
This is not a piece written to drag the success of the astonishingly strong and quick women who win races across the world. It is, however, one that acknowledges a consistent gap of about 10% between the times and distances of males and females, in general, at the same distance/time frame. This 10% figure crops up again and again, from sprints all the way through to races that last multiple days.
If anything, these stats make Entrekin's win even more impressive.
The Biological Landscape
That said, women do possess distinct physiological traits that become performance enhancing over time. They typically have a higher proportion of Type I (slow-twitch) muscle fibers, which are more fatigue-resistant and efficient for sustained efforts. Higher oestrogen levels promote fat oxidation, allowing women to burn fat more efficiently. Research has also shown that women exhibit less peripheral muscle fatigue than men after extreme bouts.
Men on the other hand have greater muscle mass, VO2 max and haemoglobin concentration in general. But these aren’t necessarily conducive to thriving in an ultramarathon environment.
Research from two ultras in 2009 found that nausea/vomiting was the primary cause for participants to not finish, with 37% of finishers experiencing it. That was in a 160KM race… so extrapolate that number out to races as large as 400KM and many of the things that hold people back, or stop them entirely, are due to issues outside of pure physical prowess. It’s a system-level signal, where the nervous system prioritises survival over digestion when the stress becomes unmanageable.
Mind Over Muscle
The question arises: how relevant is gender given the massive support systems available today?
Rachel Entrekin’s record was achieved with a six-person support team and constant refuelling throughout, something that arguably negates certain female biological advantages (like fat oxidation, if both genders can fuel with carbs throughout the race).
On the other hand, the general smaller frame of females means they have lower caloric and fluid requirements, potentially reducing the risk of gastrointestinal distress, which as mentioned is a leading cause of race failure.
To do well in ultras you need to be incredibly fit, mentally astounding and have the fates on your side to prevent excruciating blisters, mind-warping hallucinations and soul-crushing sleep deprivation from stopping you.
Entrekin herself emphasises how crucial attitude, and the ability to combat stress, are in order to succeed in ultras, stating they’re at least as important as physical fitness. Historically, women are observed to be better at pacing, being 1.46 times more likely to maintain a consistent pace in long races compared to men, who are more likely to start too fast and "burn out".
Different sports favour different heights, weights, attitudes, muscle mass and fat percentages. That’s no surprise. Whilst it can be fun (and will garner clicks) to pit genders against one another, ultimately the most impressive endeavours come from overcoming the odds. That’s why stores like Entrekins are so bloody amazing.
Expanding the Baseline of Physical Endurance
Ultimately, while the debate comparing the "fastest females" with the "fastest males" will continue, it can't diminish the extraordinary nature of these performances.
Yes, the 10% rule holds across records achieved in strict environments, but as sport continues to broaden outside of tracks and into deserts, up mountains, through forests and wherever else, there are far more variables to consider when it comes to “winning” that pure biology doesn’t account for.
Women like Entrekin are redefining the limits of human endurance. Simple as.
Her remarkable achievements will encourage female participation, which will then give us better data to paint a more accurate picture. Not that it really matters. The current reality is already incredibly inspiring. Entrekin’s jaw-dropping victory, slashing hours from the course record is a feat of human brilliance that lights a fire under anyone who pays attention. No matter what’s between their legs.
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