Do women have more stamina/endurance than men?

During the first edition of the ultra-trail of Mont Blanc Courmayeur-Champex-Chamonix, Corinne Favre completed the 86km in 10 hours, 35 minutes and 55 seconds. An exceptional time which put her in first place…ahead of almost 1000 men. “This performance blew us away,” says Guillaume Millet, researcher at the Laboratoire Interuniversitaire de biologie de la motricité (LIBM) at the University of St Etienne. It was at that moment that the scientist, who was working with a number of endurance athletes, asked himself the question: why is it that women succeed in winning ultra-trails against men whereas this never happens on shorter distances?

“There is no sport in which women are physically stronger”, recalls Guillaume Millet.” On average, they have results which are 10 to 12% lower than men.” In endurance sports, this can be explained, according to him, by a number of different parameters. First, men have blood which is richer in red blood cells (between 42 and 47%) than women (37 – 42%). However, red blood cells carry oxygen to muscles. Women are therefore, particularly disadvantaged. Moreover, the percentage of fat is also higher for women (10 to 12 % of body mass, compared to 6-7% for men for the slimmest of both sexes), which means they are carrying extra weight during a race.

Nevertheless, from time to time a woman will beat all her male competitors, in particular on a long race such as an ultra-marathon of over 100km. “In 2019, that was the case for at least 4 races,” the researcher highlights. Jasmine Paris won the 268 mile Spine Race in England; Maggie Guterl, the 250 miles Big’s Backyard Ultra in the US; Liz Marshall the 154km Grand Trail Stevenson in France and Fiona Kolbinger, the 2 500miles nonstop Transcontinent Race across Europe by bike, which leaves from Burgas in Bulgaria and finishes in Brest. “Let’s be clear, the main reason for their success is almost certainly the reduced number of participants. It is statistically more frequent that in this type of race there are only men with an average performance level who participate. A very high performing woman can therefore win the race,” the researcher explains. “That said, this is not purely anecdotal and so we are questioning whether there is a biological explanation.”

Since then, the scientist and his colleagues have developed a number of hypotheses. According to them, female metabolism may use fats more efficiently as a source of energy, which enables athletes to save their glycogen, the residual substrate for endurance sports. Second hypothesis which the researchers have tested directly: women are more resilient to fatigue and to muscle damage.
“In 2012 we compared men and women with the same relative sports performance level, in other words with the same ranking respectively for men and for women. The men exhibited more muscle fatigue at the end of long races.” To obtain this data, Guillaume Millet and his colleague stimulated the athletes’ muscles electronically and measured the strength of their muscle contraction in response, both before and after the race. They observed that this diminished less on the second reading for the women than for the men. “Although we don’t know why, it is possible that the women’s muscle fibres are more resilient”, explains the researcher. “ Another explanation could be that those muscles fibres which are specifically used for endurance and which only tire a little, take up more space in women than in men when compared to so-called quick muscle fibres which are called upon in speed races. “It is also possible that women rely on more conservative race strategies. In other words, they are less likely to hurt themselves.”

To expand upon these initial results, in 2019 the team at LIBM launched a new campaign. “We recruited 75 runners, of which 40 are women,” describes Guillaume Millet. “Then we undertook measurements before and after 5 races covering distances from 40 to 170km.” The objective of these measurements: to verify if the discrepancy in muscles fatigue between men and women increases as the races increase in distance. The initial results will be available in 2020.
One of the problems the researchers have encountered when analysing the data is the lack of publications on sportswomen. “Most studies on participants in ultra-trails ae focused on men and assume that the results are valid for both genders,” the researcher explains. However, it is possible that muscle fatigue presents differently depending on the stage in a woman’s menstrual cycle, and there is very little scientific data which allows the results to be assessed in light of that factor. “Everything remains to be done, and this represents a huge amount of work”, Guillaume Millet states.

“Moreover, it proved difficult to recruit women for the study”, he adds. “Not only those women who can beat all the men participate in this type of race, but those other women are also less numerous.” For certain competitions, women represent barely 10 % of the total number of participants, which makes it difficult to compare male and female athletes at the same level. However, since 1967, the date of the first female participation in a marathon – Katharine Switzer who ran the Boston Marathon without being authorised to do so – we know that women have no physiological difficulty in completing long distances. “The reasons for the absence of women in this type of race are sociological of psychological”, concludes Guillame Millet. He cites, among other possible explanations, self -censorship, other additional burdens in daily life in a context in which training for this type of race is very time consuming, or even the possibility that women have less of a need to prove that they are capable of this type of sporting exploit. “But that is outside my domain,” he laughs.

[Translated from the article published in the National Geographic on Wednesday 18 December 2019 by Taïna Cluzeau]