Why Women Are Overtaking Men At Extreme Sports Like Ultralong Distance Skiing

In 1985, Libby Riddles sent shockwaves through arrogant men in the frozen north, if not worldwide, by winning one of the world’s toughest races. The Iditarod Trail Sled Dog Race requires competitors and teams of 12-16 dogs to race across 1,510 kilometers (938 miles) of snow. The journey takes at least a week, often through conditions that would cancel almost any other sport. So many dogs have died competing that major sponsors have pulled out.

Riddles’ victory inspired t-shirts reading “Alaska: where men are men and women win the Iditarod”. Another woman, Susan Butcher, won four of the next five races, smashing the record time in ‘86 and breaking that time twice more. Emphasizing how tough the contest is, 1985 might have had women first and second if two of Butcher’s dogs hadn’t been killed by a moose. Iditarod winners since have all been male, but the myth of male physical supremacy took a serious dent.

Since then, women have claimed a number of titles in extreme endurance challenges such as open ocean swimming. Given the substantial gap that remains between the male and female world records in shorter sports, this has inspired decades of speculation about why endurance contests are different. A team from the Universities of Montana and Wisconsin set out to explore this using a different Alaskan event where men and women cover the same ground, the Alaska Mountain Wilderness Ski Classic (AMWSC).

Unlike the Iditarod, the Ski Classic uses no dogs, so winning can’t be attributed to a better team or ability to handle them. Instead, competitors must cross 160-289 kilometers (100-180 miles), depending on the year, alone and without assistance. The extreme conditions led scientists to study the energy requirements and effects on body composition in 2016. Newly published research does something similar, and considers how the results are affected by sex using eight female and 12 male competitors.

The AMWSC is not a race, with no awards for fastest completion. Nevertheless, entrants push themselves to get through it quickly, if for no other reason than to get home to a bath. (Avoiding the next blizzard is probably also an incentive). On average, the women took half a day longer than the men to complete the course (8.1 days versus 7.5), but the top female performers had times very similar to the fastest men. 

Women expended less energy in the process, the authors report, and also had a lower energy expenditure to total load carriage (body weight plus food, clothes, and camping gear carried). Both showed some of the highest total energy expenditure for their sex ever recorded over multiple studies. The authors of the new study attribute this, in part, to the fact that cold exposure increases resting metabolic rates.

The authors think the differences they observed between the sexes are consistent with “those [studies] that show women to be potentially more resistant to performance fatigability.” They think this may, in part, be because women, on average, draw more of their energy over long periods of time from lipids and may have greater mitochondrial oxidative capacity.

The difference in performance between male and female elite athletes in most sports has a biological component, although intersex conditions and non-standard sex chromosomes make this more complex than usually described. However, social factors also contribute – most notably, girls are far less likely to be encouraged to start sports than boys today, let alone in the past. Determining the relative influence of the two is not currently possible. 

However, it’s clear that male advantages diminish as contests get longer. Until 1972, women were banned from the Boston Marathon, and the one woman who tried to run in 1967 was famously assaulted by the race manager, following claims the previous year that women were incapable of running the distance. Today, the women’s marathon world record is less than 8 percent slower than the men’s, and the gap is closing relatively quickly. Meanwhile, the difference is about 10 percent for most short and middle-distance records, with the gap closing more slowly.

If, as seems possible, the factors the study identifies lead to women eventually consistently outperforming men in certain endurance sports, responses will be interesting. Will endurance events currently open to both sexes become separated so men have a chance? 

The findings may also prove relevant outside sports. Recently, an Australian political candidate was dumped by his party for saying the country’s military “need to remove females from combat corps […] because they can’t cope with the carrying of the heavy loads and the heavy impacts.” For missions to remote areas without support for a week or more, however, there may come a time when men appeal to DEI principles to get chosen.

The study is open access in Frontiers in Physiology.