Resting heart rate?

With only 99 seconds to spare, Jasmin Paris became the first female to finish the Barkley Marathons, writing herself into ultrarunning legend for the second time in her career. The 100-mile course includes around 16,500 metres of climbing – about twice the height of Mount Everest – over brutal terrain and a strict 60-hour time limit. Since 1989, more than 1,000 athletes have attempted the self-navigated, five-loop race, but only 20 have ever finished the full distance.

Advertisement - Continue Reading Below Montane Winter Spine, a 268-mile race over the Pennine Way, where she set a new women's course record – which was, at the time, 13 hours faster than the men’s record. All while, she was pumping milk for her 14-month-old daughter along the way.

The longer the race, the more likely we are to hear of such an outstanding female performance or overall female winner. In 2017, Courtney Dauwalter won the I always thought I could do it, Health & Injuries.

Achievements such as Paris’s and Dauwalter’s have led many to conclude that, as the distance increases, the gap between male and female performance declines, and that some aspects of female physiology give rise to an advantage as the duration of events increase. In 2020, RunRepeat’s Are women better endurance athletes than men supported this argument, finding that in races longer than 195 miles, women finish, on average, faster than men.

What does the research say?

RunRepeat's study analysed 5,010,730 results from 15,451 ultrarunning events over 23 years, concluding that the longer the race distance, the shorter the gender pace gap. At the 5K distance, men ran 17.9% faster than women, but at the marathon distance, this reduced to 11.1%. Over 100-mile races, men only had a 0.25% advantage, and for races above 195 miles, women were recorded as 0.6% faster than men.

These findings, alongside some headline-grabbing performances, have promoted calls for longer races to remove the female category entirely. If women are equally likely to win and if there is no physiological disadvantage at longer distances, then surely there is no need for a separate female podium and prizes?

Trent Stellingwerff, Senior Advisor, Innovation & Research at the Canadian Sports Institute Pacific, disagrees with this conclusion: ‘Testosterone is a long-term longitudinal exposure variable. Post-puberty, men have higher muscle mass, strength, power, a 10-20% higher VO2 max, higher blood volume and more. There is still a 10-12% physical advantage to being a male runner, which is shown by race data in highly competitive events.’

This fits when we look at world record variation between men and women across different events. At 100 metres, the men’s record is 9% faster than the women’s – at 5K, it is 11%. From marathon distance upwards to six-day ultramarathons, the gap between the male and female performances increases slightly with distance, with a gap of 17% in 100-mile records and 15% over six-day races.

This can be demonstrated further in the winning times at the most competitive longer ultramarathons in the world. Jim Walmsley’s 2023 UTMB course record is 15% quicker than Courtney Dauwalter’s 2021 record. His Western States record, set in 2019, is also 9% quicker than Dauwalter’s set last year.

Despite women outperforming men in some events, where there is competitive depth or at the highest level of the sport where world records are broken, male athletes maintain their advantage over all distances.

So, how can we account for RunRepeat's findings that this advantage disappears as the race distance increases? ‘When making sex-based comparisons between men and women, you need to look at whether the data is normalised between the pools,’ explains Stellingwerff. ‘Here the competition pools are different; the inclusion is different. Of those five million athletes, we have perhaps four times more men than women. There are a whole bunch of slower men bringing down the male average. If we compared the top male finishers to the top female finishers, there is a performance gap.’

What’s happening is that those women in the ultra-endurance events are, typically, more elite or experienced than the men. When asked her thoughts as to why this is, Paris recounted her first experience at Dragon’s Back, a 240-mile stage race across the Welsh mountains: ‘Helen Diamantides [a renowned fell runner] said to us at the start of the race: “Look around the room. If you’re a man in this room, you have a 50% chance of finishing. If you're a woman, you have a 90% chance.” This was based on event statistics. There were far fewer women on the start line, but the women were much better prepared. I guess we have less ego, whereas men assume it can’t be that hard!’

So, in the same way that a team of female club runners would outpace novice men over a 5K event, women in longer races are just relatively more experienced athletes.

Why women are more prepared for longer races

SheRACES research shows that 50% of women have been put off a race because of its cut-offs, only entering if they’re highly confident they can complete a race within the time limit. Women are also more focused on the logistical details of a race, as well as having the right skillset to ensure they’re fully prepared.

Paris finished the Barkley Marathons on her third try, having focused on learnings from her first two attempts. To prepare, Paris added some orienteering events to her training schedule, and her family supported her by setting up practice Barkleys, which included hidden books. (The race itself requires runners to locate books on the course and extract pages matching their race number to prove they have completed the full distance.)

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Given that the physiological gap between men and women doesn’t diminish over longer distances, why do we see exceptional performances such as Paris’s and Dauwalter’s, where a woman finishes ahead of all the men?

The longer the race, the more factors that also come into play. ‘At the Barkley, you have to be able to climb a huge amount in 60 hours, and cover ground at a fairly decent pace,’ says Paris. ‘There are physiological differences between men and women that make that more possible for men at the top of the field. But the Barkley is not just about pure strength. It’s as much about navigation, mental tenacity, the ability to look after yourself and feed yourself, and being able to keep picking yourself up and going back out there – areas where women might be stronger than men specifically on this race.’

Best and worst ab exercises for runners The Green Runners found that higher testosterone leads to higher risk taking in males, including pacing strategy and navigation, which may also play a role in failure at extreme events such as the Barkley Marathons. Paris explains the impact of this: ‘The course has got longer and harder [over the years]. There used to be time for people to sleep between laps, but only one finisher slept this this year, and only for 20 minutes. There’s time to make navigation errors, but the key is that you recognise and correct them quickly, you don’t panic and you never truly lose track of where you are. Descending into a wrong valley and having no clue where you are is irredeemable.’

With longer-distance events, the chances of the best woman being faster than the best man on the day increases. As races exceed 100 miles, athletes have to be able to manage sleep deprivation and temperature changes, continue eating and drinking, and navigate and push through the inevitable pain in multiple areas of the body. There’s far more that can go wrong here than in a marathon.

These multiple factors make each runner’s finish time more volatile, and increases the likelihood that any runner fails to complete the course at all. Combined with the number of athletes in the field usually being small – in the hundreds rather than thousands – this increases the likelihood of an outlying performance by a woman.

Barriers preventing increased female participation

Could we see more women crossing the finish line first in future? And what changes need to be made to make that happen? Women are still a minority on ultramarathon start lines, which is amplified the longer the race distance. International Trail Running Association data for 2023 showed that women made up 24% of starters at 50K races, but this fell to 18% for 100K races and less than 14% for races of 100 miles and beyond.

The barriers to non-elite female athletes competing in ultramarathons, resulting in this low participation, are partly societal, with women having less free time to train than men and lower confidence in their ability to take on such challenges. But they are also partly due to the design of the races themselves, from tight cut-offs that penalise more women, to promotional imagery focused on faster men, discouraging novice women from entering. ‘In my experience, women are put off by races billing themselves as “the toughest” and “most extreme”,’ agrees Paris.

On top of this, many races still don’t take the needs of female athletes into account, offering insufficient toilets, no period products and only male-fit (often dubbed ‘unisex’) T-shirts.

Even elite female athletes, who are not put off by cut-offs and have the potential to be first to cross the finish line, still face barriers to participation. SheRACES has been working with the Pro Trail Runners Association (PTRA) to reduce some of these, such as developing guidelines specifically for those races with elite athletes. These include ensuring equal media and race coverage, prize money and elite field size.

Coverage matters, as athletes rely on visibility to negotiate higher contracts with brands, which allows them to be better supported and compete in peak physical condition. A study in irunfar in 2017 found that, while 71% of male elite athletes received more than $10,000 per year, 71% of female elite athletes received $10,000 or less. The PTRA, which athletes need a paid sponsorship contract to join, has 28% more male members than female.

Elite field size is also key. For the Barkley Marathons, Lazarus Lake, the race director, handpicks every entrant. And yet, reportedly (as entrants are not announced), he selected only three women to run alongside 37 men. On that data, the female finish rate was higher than the men’s!

Other races are levelling the elite field, however. At Ultra Trail du Mont Blanc (UTMB), elite qualifying places for men and women are equal in number for each distance (50K/100K/100M), giving equal competitive depth in each race. Since 2023, this also includes the number of age group qualification places.

One other important barrier for elite athletes is motherhood. Ultra-endurance athletes appear to peak later in life than for shorter distances – right when many women start families or look after young children. Camille Herron, who recently broke 12 world records at Lululemon's six-day FURTHER event, is 41 and describes herself as ‘ageing like fine wine’. Courtney Dauwalter, who broke both the Western States and Hardrock 100 records in 2023, is 39, while Jasmin Paris is 40.

Pregnancy and postpartum recovery alone mean an elite athlete cannot compete for potentially several years. Even once a mother has regained full fitness, the responsibility of having young children makes racing harder – though perhaps this should be felt equally by male athletes. ‘I’ve had two children in the past seven years,’ says Paris. ‘So going away to the States for a week now is much harder. I waited until my son was 20 months old for my first attempt at Barkley, but even then I wasn’t sure I could leave him.’

For elite athletes, just getting places on the right start lines can be difficult postpartum. While many trail races now offer pregnancy deferrals for non-elite women, for elite athletes they determine entry by various indexes (ITRA or UTMB), which are based on an athlete’s recent performances. SheRACES is campaigning for these indexes to be frozen for a period of time if an athlete becomes pregnant, so she can have access to elite race entries as soon as she is ready.

Addressing the science of female endurance

Many leaps in running performance over the past few decades can at least be partly attributed to sports science – from fuelling to acclimatisation and cooling, to training methods and, of course, to the creation of super shoes. But, most of these studies have only been carried out on men, so elite women have not yet seen the same benefits.

‘I fell into doing women’s research through my amazing wife,’ says Stellingwerff, referring to his wife Hilary, who was a double Olympian in the 1500 metres. ‘Every time something came up in her running career, as a scientist I would go to the literature and there was nothing there. Things like altitude and anaemia, iron in females or elite female runners returning from pregnancy. There are gaps around metabolism when it comes to extreme events and females. There are gaps in and around how sweat and hydration work, fatigue and durability, if and how menstrual cycles impact performance. Most of our fuelling and nutrition advice – how much carbohydrate to take per hour in endurance racing – is probably based on 90%+ male participants. Women can have fat oxidation levels 25-50% higher than men at the same relative intensity. So, especially for the longer events, women might not need as much fuel.’

The recent Lululemon FURTHER project prepared 10 women over 18 months to run a six-day event, where each would go on to run further than they had ever done before. Far more than a race, this was a research project, seeking to understand female endurance and, most importantly, to derive learnings to arm women with the knowledge on how to perform at their very best. Camille Herron said the project offered ‘the best support I’ve had in my running career, helping me to optimise my health and performance. It shines through in all my performances and world records the past year. Women have different bodies and needs.’

During the multi-day event, athletes had continuous glucose monitoring, core temperature pills, daily blood draws and biomechanical reviews. While Stellingwerff, who was lead researcher on the project, cautions that with a limited data set it will be hard to make definitive recommendations, he anticipates that we will be able to ‘characterise female ultrarunners like never before’ – closing the knowledge gap to help women to truly reach their limits.

Looking to the future

A woman finishing the Barkley Marathons has been described as the last glass ceiling for female ultrarunners, with Courtney Dauwalter herself publicly thanking Paris: ‘I’m so impressed by her – and thankful to her for just blowing the roof off the thing and showing us what’s possible.’ At the limits of human endurance, mental belief, determination and sheer will to endure suffering are perhaps far more important for performance than miles run in training – or even our physiology.

Paris’s self-belief is evident – ‘I always thought I could do it!’ – and something she is passionate in wanting to pass on to other women. When Paris was asked what legacy she wanted her Barkley finish to leave, she replies: ‘Obviously the support for Stravas 2024 Year in Sport report is here and promoting a more sustainable way to run. [She ran all three Barkley attempts in the same pair of trail shoes, and now intends to focus on adventures and races closer to home.] But also for women and girls to believe in yourself and try to challenge yourself, as you never know what you might achieve.’