The rain is horizontal. The trail ahead has dissolved into darkness, mud and exhaustion. Somewhere beyond the next ridgeline you know there is a checkpoint, but it could be five minutes away, or it could be an hour. Your legs have stopped cooperating with you, and your mind is bargaining with itself, every instinct is telling you to stop, and yet, somehow, you keep moving.
This is the world of ultra-endurance sport; a place where ordinary assumptions about human capability are dismantled one painful step at a time. For many women, the greatest challenge is usually not the distance itself, but rather it has been overcoming generations of people insisting they shouldn’t be there, they don’t belong, or that they aren’t physically capable.
At this year’s Fort William Mountain Festival, journalist, coach and ultrarunner Lily Canter brought to the stage a story that felt both long overdue and urgently relevant. Drawing on the research and stories from her celebrated book Ultra Women: The Trailblazers Defying Sexism in Sport, co-authored with Emma Wilkinson, her talk explored a provocative question; what if women aren’t just capable of competing in ultra-endurance sport? What if they have been uniquely suited to it all this time on a biological and evolutionary level, more so than men?
For centuries, women were told that endurance was not for them. Their bodies, they were warned, were too fragile, too emotional, too unpredictable. The prevailing wisdom of the day insisted that running, swimming or cycling long distances could damage women’s health, compromise their fertility, or simply exceed their natural capabilities. Today, those arguments sound absurd, yet they shaped sporting culture for generations.
In 1967, race officials infamously attempted to physically remove Kathrine Switzer from the Boston Marathon because women were not permitted to compete. It wasn’t until 1984 that women were finally allowed to race the Olympic marathon. Even now, much of the scientific research that underpins sports performance, training and recovery has historically focused on male athletes. For years, women have frequently been excluded from studies because their hormonal cycles were considered too complex or too variable to analyse. As a result, much of what we understand about training, recovery and performance in endurance sport has been extrapolated from male physiology and then applied universally. This male centric approach has left female athletes navigating everything from fuelling strategies to injury prevention with surprisingly little evidence designed specifically for their bodies. It is only in recent years that researchers have begun to explore how factors such as the menstrual cycle, pregnancy, postpartum recovery and menopause influence endurance performance, revealing just how much knowledge has been overlooked.
The consequences of this research gap extend beyond physiology into the very equipment athletes rely upon. Much of the kit used in endurance and mountain sports; from hydration packs and running vests to waterproofs, backpacks and safety equipment; has historically been designed around male body shapes and proportions, with women’s versions often amounting to little more than smaller sizes or different colours. Even nutritional advice in endurance sport has traditionally been based on studies of male athletes, despite emerging evidence that women metabolise fuel differently during prolonged exercise and may have distinct nutritional requirements for optimal performance and recovery. For generations of female endurance athletes, success has therefore required not only extraordinary physical resilience, but also the ability to adapt, experiment and excel in systems that were never truly built with them in mind.
And still, throughout this time, women ran, swam, rowed, and biked. They did so unofficially, they did so unsupported, they did so despite mockery, exclusion and neglect. They did so because something inside them demanded movement, challenge and freedom. The stories Lily outlines in Ultra Women feel so powerful because they are stories of defiance in the face of the status quo, rather than being solely examples of athletic achievement.
The story of aforementioned Kathrine Switzer at the 1967 Boston Marathon is one of the most important moments in the history of women’s sport, not just because of her taking part, but because the photographs of what happened became a global symbol of women’s fight for equality in sport. In the 1960s, the belief among sports authorities was that women were physically incapable of running long distances. The governing body for American athletics prohibited women from competing in races longer than 1.5 miles. Boston Marathon organisers shared this view. Switzer was a 20 year-old student and experienced runner. She entered the race using initials she always signed in lieu of her full name: “K.V. Switzer.” Her application was accepted, she paid the entry fee and was assigned a bib. She lined up at the start, and initially the atmosphere was supportive, with many male runners encouraging her participation. About two miles into the race, a press vehicle realised there was a woman wearing an official race bib. One of the race directors, Jock Semple, became enraged and leapt from the press truck, ran towards Switzer and grabbed her. According to Switzer’s own account, Semple shouted: “Get the hell out of my race and give me those numbers!” Photographers captured the moment as Semple attempted to tear the race number from her chest. A male competitor tried to protect her but was knocked aside. Then Tom Miller, a former American football player and hammer thrower, body slammed Semple off the course, allowing Switzer to continue running. The photographs of a furious male official physically attacking a female athlete were published around the world. A humiliated Switzer later recalled that for a brief moment, she considered quitting, but then realised if she did, people would say women really weren’t capable of running marathons. After four hours and 20 minutes, Kathrine Switzer crossed the finish line, becoming the first woman to officially complete the Boston Marathon.
Kathrine Switzer found herself about to be thrown out of the normally all-male Boston Marathon when a companion, Thomas Miller, threw a block that tossed a race official out of the running instead, April 19, 1967 in Hopkinton, Mass. (Harry Trask, Public domain, via Wikimedia Commons)
Using the photographs of her confrontation, Switzer spent the following decades campaigning for women’s distance running, helping to create international women’s road races and lobbying for the inclusion of the women’s marathon at the Olympic Games. Her efforts contributed to women being officially admitted to the Boston Marathon in 1972 and to the women’s marathon becoming an Olympic event in 1984.
88 years before the women’s marathon being officiated at the Olympics, Stamata Revithi was a Greek woman denied entry to the first modern Olympic marathon in 1896. She was living in poverty and mother of a young child. Hoping to find work, she travelled to Athens, where she became aware of the excitement surrounding the inaugural Olympic marathon. According to contemporary accounts, Revithi had always enjoyed running long distances. She reportedly met a man who suggested that if she ran the marathon, she might gain publicity, recognition and perhaps even employment. She decided to try.
The 1896 Athens Olympics were intended to revive the spirit of the ancient Games, and the founder of the modern Olympic movement, Pierre de Coubertin, strongly opposed women’s participation in sport, thus women were barred from all Olympic competition.
Nevertheless, Revithi travelled to the village of Marathon, where the runners were gathering for the race. Newspaper reporters were fascinated by her presence. Not surprisingly, the organisers refused her entry. Rather than accept defeat, Revithi returned the following day and ran the entire course alone. Before setting off, she asked the mayor, a teacher and a magistrate to sign a document confirming her start time. She then ran the approximately 40 km route from Marathon to Athens entirely by herself, in around five and a half hours, an extraordinary achievement given the conditions, the lack of support and the fact that she was effectively conducting her own unofficial athletic experiment. When she reached Athens, however, she was prevented from entering the Panathenaic Stadium, where the official marathon had finished the previous day. Instead, military officials stopped her outside and signed documents verifying that she had completed the course. Revithi planned to submit these to the Hellenic Olympic Committee in the hope of obtaining official recognition. There is no evidence that she ever received it.
More recently, few contemporary athletes embody the spirit of ultra-endurance quite like Lael Wilcox. In 2024, the American ultra-cyclist shattered the women’s world record for circumnavigating the globe by bicycle, riding more than 18,000 miles across 22 countries in just 108 days, 12 hours and 12 minutes, beating the previous record by more than two weeks. She has also won some of the world’s toughest unsupported bikepacking races, including the Trans Am Bike Race and the Tour Divide, often competing directly against, and defeating, elite male riders. Long before ultra-endurance became a mainstream phenomenon, swimmer Lynne Cox was quietly reshaping the boundaries of human possibility in some of the world’s most hostile waters. As a teenager, Cox twice broke the record for swimming the English Channel, becoming the fastest person, male or female, to complete the crossing in 1972 and again in 1973. But it was her extraordinary cold-water swims that cemented her place in endurance history. In 1975, she became the first woman to swim New Zealand’s notoriously treacherous Cook Strait, and in 1976 she became the first person ever to swim the Strait of Magellan. Most remarkably of all, from a geopolitical angle, in 1987, she swam from the United States to the Soviet Union. She credits her ability to swim in incomprehensibly cold temperatures to her female body – carrying more body fat than a typical male counterpart.
Lynne Cox. Photo credit Michael Muller
And then, famously, there is Pentlands-based Jasmin Paris, whose astonishing outright victory in the 2019 Spine Race, and only female completion of the grueling Barkley Marathons, became defining moments in modern ultra-running history. Covering 268 miles along the Pennine Way in winter conditions, she not only broke the Spine course record but did so while expressing breast milk for her infant daughter at checkpoints. It was a performance that shattered stereotypes about motherhood, endurance and what women are capable of achieving. The photograph of Paris, at the end of the 2024 Barkley, collapsed by the gate in Tennessee’s Frozen Head State Park has become one of the most famous moments captured in sport.
Jasmin Paris at the Barkley Marathons. Photo credit @Howie-Stern
These women rewrote narratives, as well as broke records. Yet perhaps the most fascinating aspect of Ultra Women lies not in its historical stories, but in the scientific questions it asks; could women actually possess biological advantages in ultra-endurance sport?
For decades, sport has operated on a simple assumption: men are naturally stronger, faster and therefore superior athletes. In many disciplines, differences in muscle mass and physiology support this view. But ultra-endurance events operate by different rules. Success depends not simply on explosive power, but on energy efficiency, pacing, pain tolerance, resilience, recovery and the ability to endure discomfort over extraordinary periods of time.
Emerging research suggests that women may hold advantages in several of these areas. Women tend to metabolise fat more efficiently during prolonged exercise, preserving precious glycogen stores. Some studies suggest they may experience fatigue differently and demonstrate more effective pacing strategies. Psychologically, many elite female athletes describe a willingness to tolerate discomfort and uncertainty that becomes a powerful asset when events stretch into days rather than hours. One of the most persistent myths in sport is that pregnancy marks the end of athletic ambition. In reality, pregnancy and childbirth are among the most intense endurance challenges the human body can undertake. Over the course of nine months, the body adapts dramatically; blood volume increases, the cardiovascular system works harder, energy demands rise, and muscles, joints and hormones undergo extraordinary change. Yet many female athletes return to competition not diminished, but even stronger than before. Emerging research suggests that the physical and psychological adaptations associated with pregnancy, childbirth and parenthood may, for some women, enhance resilience, perspective and endurance capacity.
Of course, there is no single explanation for greatness. Every athlete, regardless of sex, arrives at the start line carrying a unique combination of biology, experience, training and determination. The point isn’t whether women are definitively better at ultra-endurance sport. Perhaps the point is that we have spent far too long asking the wrong questions.
For generations, women have been required to prove that they belong on the start line, to justify their participation, to defend their ambitions. To overcome social barriers. The women featured in Ultra Women remind us that sporting progress has rarely been gifted, more often than not, it has been fought for.