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What Makes Women Strong?

Science is revealing that when it comes to physical prowess, women may actually be the more powerful sex

WWhen she was 80 years old, my grandmother built a new stone wall in her garden. She’d constructed many of them during her “retirement” — years that she also spent raising me, running the local ambulance corps, and landscaping her three woodsy acres in New York’s Hudson Valley. The walls were integral to her garden designs.

Sporting a terry cloth headband that slowed (but didn’t stop) the sweat sluicing down her cheeks, she lifted and placed the recalcitrant mini-boulders — leftovers from ancient retreating glaciers — into harmonious position, like a slow dance. “It’s a physical and mental puzzle. A great challenge,” she said.

The hip-high stone construction still stands at her former home. It was not her first wall — but it was her last. When she died at 82, my grandma’s thighs were still tough with muscle and her hands calloused from physical labor.

Women get their own category for feats of strength: a separate one, often tied into the tasks of caretaking or motherhood.

Growing up with my grandmother from the age of 4, she was my example of strength and womanhood. But popular culture (especially my favorite ’80s TV shows) and societal consensus around gender “roles” eventually taught me that whether it was carrying a bag of groceries, or shoveling a snowy driveway, it is custom that a man’s help — or even a boy’s — should be enlisted. Men are strong, and women lean on that strength.

Women get their own category for feats of strength: a separate one, often tied into the tasks of caretaking or motherhood. Nobody hesitates to ascribe strength to what women go through in childbirth, or marvel at the power of the woman who pushes a car off her crushed child. But flexing our strength outside those strictures renders women somehow weird or deviant — especially when it comes to athletics.

As seen in the cases of athletes like Olympic weight lifter Sarah Robles, British heptathlete Jessica Ennis-Hill, and tennis star Serena Williams, when a woman performs at the top of her game, her femininity is often questioned. “As a female athlete, people want to draw out your masculine traits that make you successful — as opposed to your female traits that have made you successful,” says Jennifer Pharr Davis, author of The Pursuit of Endurance.

Davis describes herself as tall with large calf muscles, and she says people often tell her that it’s these “manly” traits that allowed her to hike the entire 2,200-mile Appalachian Trail in 46 days, 11 hours, and 20 minutes. (She held the record for the fastest known time (FKT) on the trail from 2011 to 2015.) Davis says this masculinization of her achievement bothers her: “It’s interesting to me that you’re taking away who I am to make yourself more comfortable with my accomplishment,” she says.

Men as a class do have areas in which they are generally more physically able than women. In a random group of 100 people, men can lift heavier things with their upper bodies, because they have more upper-body muscle. Generally, men can run short distances about 10% faster than women due to larger hearts, leaner muscles, and some other muscle efficiencies. But there are other areas where women are generally stronger than men, like accuracy, flexibility, and endurance. As more women continue to enter competitive athletics, and as the emerging science on women and strength increases, the definition of strength becomes much more nuanced.

AAll athletes are improving — that’s the nature of setting new records. Because women have been competing for significantly fewer years than men in almost every sport (for instance, women didn’t compete in all the same track events as men until the 2008 Olympics), their gains are bigger and faster. The first woman was allowed to run the Boston Marathon in 1971. In the years since then, women’s race times have improved by leaps and bounds, while men’s improvements have been more incremental: “In 1976, the world record for men was 2:08:34 and for women 2:38:19… a difference of 18.71%. Since then, the best male performance has dropped just 2.83%, to 2:04:55. Meanwhile, the best female performance has plummeted an astonishing 14.46% to 2:15:25,” according to a 2012 paper that looked at the history of marathon times. These gains were made even though women still haven’t reached “competitive parity” with men. That’s determined by looking at the top 10 times in almost any competition — the guys will have similar finishing times, whereas there are larger gaps between the top women, indicating a less dense field of competitors. Sandra Hunter, a professor of exercise physiology at Marquette University, has calculated that about 34% of the gap between men and women’s race times is down to disparities between how many more men participate than women.

Similar gains can be seen in other sports, like swimming. At the Olympic level, Johnny Weissmuller won two gold medals in the 1928 Olympic Games, one of which was for the 100-meter swim. (He was the first to break the one-minute record for that race at 58.6 seconds.) Any modern-day female competitive swimmer would be able to beat his times handily — and they have for decades.

As more women compete — and women athletes get more experience — they will continue to set new benchmarks. “We haven’t got anywhere close to maxing out our genetic ­capabilities yet,” Rebecca Rusch, a world champion mountain biker who competes with men, told Outside. Women might even outpace men in shorter events: One study suggests that a female sprinter might beat a man by the 2156 Olympics (based on their current trajectory of improvement over time), though others predict that in shorter events, men will always have a small advantage.

OOne of the biggest challenges impacting women’s ability to compete is the lack of scientific information when it comes to female bodies and exercise. Women weren’t regularly included in exercise physiology and biomedicine studies until 1993, when President Clinton passed a bill that required that women be included in all National Institutes of Health (NIH)-funded Phase 3 trials (although a 2007 analysis showed that many researchers still weren’t meeting the requirement.) In 2014 the NIH updated its rules to mandate that female mice had to be included in animal studies, but a recent review shows that test subjects are still only about 20% female.

There are many excuses for the lack of gender parity in research, says Stacy Sims, a senior research scientist in exercise physiology at the University of Waikato in New Zealand. “I’ve heard things like, ‘We don’t know enough about men; why do we want to study women?’ Or it’s that ‘women are too different’ or ‘there’s not enough funding,’” says Sims. Menstrual cycles are often blamed for making results too complex but Hunter calls that excuse “rubbish.” The fact is that many variables are compensated for in exercise physiology studies: “There’s other characteristics such as stress, prior physical activity, or nutrition which we don’t blink about controlling for,” says Hunter.

“In humans, men, but not women, self-reported higher levels of stress when tested in a room previously associated with tonic [chronic] pain.”

Despite this limited research, what scientists are learning about women’s bodies — and strength in general — is compelling. It also is leading them to question how strength is defined.

Strength is often characterized by an ability to withstand pain — like continuing a race even through intense discomfort. Studies disagree on whether women feel pain more or less severely than men since there is a strong cultural element to reporting one’s own pain perception. Regardless, data shows that women appear to be less stressed by pain. A recent study of both mice and humans found males were more sensitized to pain, and remembered it more clearly: “In humans, men, but not women, self-reported higher levels of stress when tested in a room previously associated with tonic [chronic] pain,” the researchers wrote. This may give women an advantage. Take, for example, the 2018 Boston Marathon. The day of the race it poured rain and temperatures were freezing. But a look at the final figures showed that women were substantially more likely to finish the race than men. The dropout rate for the race was up almost 80% for men from 2017, but among women it was up only about 12%. It was a trend that was present even among elite runners, the New York Times reported.

If discussions of human physical strength used endurance as the yardstick, women would be strongest. Women have already caught up to, or surpassed, men in some sports like long-distance swimming and ultrarunning, racking up the wins in mixed-gender races (with less support and training than the men). Recently, Camille Herron won 2018’s Desert Solstice run, which lasts for 24 hours (she ran 162.9 miles in that time) and Courtney Dauwalter has won 11 mixed-sex ultramarathons, including the Moab 240, a 238-mile race along the Colorado River in Utah. Dauwalter beat the next-fastest competitor there, a man, by 10 hours.

In fact, plenty of research points to the idea that the longer the distance, the better chance a woman has in beating a man, possibly due to a combination of factors like high pain tolerance and less muscle fatigability. There could also be metabolic reasons — some researchers theorize that women burn energy in a way that supports long-distance energy needs. As investigative reporter David Epstein notes in his book, The Sports Gene, when a man and a woman are evenly matched, “the man will typically beat the woman at distances shorter than the marathon, but the woman will win if the race length is extended to forty miles.”

It’s not just on foot that women have endurance advantages: In the 28.5-mile Catalina Channel swim, considered part of the “Triple Crown of Open Water Swimming,” the fastest woman was 22 minutes faster than the quickest guy, and overall, according to an analysis, “the annual fastest women crossed the Catalina Channel faster than the annual fastest men.” Diana Nyad is the first and only person who swam the 110 miles from Cuba to Florida — and she did it without a shark cage for protection.

Hormones may also give women an edge in endurance sports. Testosterone — which is important for the health of both sexes — has long been offered as the reason men can build bigger muscles. But estrogen (which is produced mainly by the ovaries, but also by fat tissue) may regulate how nutrients are used when the body is under physical stress: “Estrogen may promote endurance performance by altering carbohydrate, fat and protein metabolism,” writes Mia Schaumberg, a researcher at the University of Queensland in Australia, in a 2017 study. And because women tend to carry more body fat than men, they may be able to utilize those stores in longer-distance races.

Women’s muscles also tire less easily, which is something Hunter, the professor of exercise physiology at Marquette, has been researching since the beginning of her career. As a postdoc, she first got interested in the idea when she was doing a simple test looking at how long people could push with their hands against a weighted mechanism — the major muscle tested was the bicep. Hunter tested herself and could go for 20 to 30 minutes at a time, but the “big burly guys” who came into her research lab could often push for less than 10 minutes. When she tested a wide sample of people, she found that overall, women could push for twice as long as men at weights that were 20% of the maximum weight each person could push.

Hunter hadn’t expected such a difference in results. “Nobody had really looked at this. It became a profound study,” she says. Hunter has continued to study this phenomenon. “On the whole, women have a muscle fiber makeup that’s able to lift less [than men], but women have the ability to drive their muscles harder,” says Hunter. She’s now delving into the metabolic reasons for this difference, but women’s muscles getting less tired over long-distance pursuits is one good reason for endurance ability.

Women are also bodily powerful (the definition of strong) in other ways: Women are also more flexible. “Women tend to have somewhat more laxity in their tendons than men; they are more limber,” Dr. Steve Jordan, an orthopedic surgeon at the Andrews Institute for Orthopaedics and Sports Medicine, told the New York Times. Limber people are less likely to get hurt — less time spent on the sidelines or in surgery. Woman also have a very high degree of accuracy — and depending on the physical pursuit, that can make one athlete stronger than the next. Women on the Ladies Professional Golf Association tour regularly significantly outdrive professional men. And according to the National Rifle Association’s Colonel Kenneth Haynes — a military logician in the Army who taught both men and women to shoot over a multi-decade career — women shoot guns more accurately: “My units had around 20 percent female personnel in both officer and enlisted ranks. All the women fired Expert their first day, but less than a third of the men did so,” writes Haynes.

TThese recent knowledge gains around sex-based variabilities are so nascent and limited that many coaches and trainers still have to rely on information found in experiments on men, which can lead to ill-informed training. “Estrogen allows a woman athlete to access more fatty acids, which means more fuel over a longer time period… but women aren’t always trained with this in mind,” Sims says. She also argues that a common tactic among women athletes — stopping their menstrual cycles during competition — may actually be keeping them from achieving their best times.

Women who compete against men do better than when they compete against just women.

It also makes for bad science: “Non-physiological factors such as the sex bias of studying more males than females in human and animal experiments can also mask a true understanding of the magnitude and mechanisms of sex-based differences in physiology and fatigability,” writes Hunter in a 2014 article in the journal Acta Physiologica.

The lack of science may hold women back in an even more visceral way: Without accurate information, they may underestimate their own potential.

True competition pushes all athletes further than they can conceive: Both men and women return better times when competition is tougher; so women who compete against men (who generally have better times for the reasons cited above) do better than when they compete against just women. Davis learned this when she went for the women’s FKT on the Appalachian Trail and felt disappointment when she got it. Why? She really wanted the overall FKT record — and she went on to achieve it. “I knew I had limited myself based off gender. But my body showed that I could compete with the men in a way that my mind had not expected,” says Davis.

Kids’ soccer in Barcelona recently proved the same point: This past season, the under-14 and under-12 girls’ teams played against boys the same age; the girls trounced the boys handily. The girls played harder in the mixed teams, and playing with boys “really makes them perform better,” Maria Teixidor, a women’s soccer board member for the Barcelona league, told the New York Times. There’s no reason to separate kids into girls’ and boys’ sports teams of other kinds, either: The Women’s Sports Foundation has shown that before age 12 there aren’t many physiological differences in athletic ability between boys and girls (and no statistical variation). Davis says this false idea of “separate but equal” was exactly what initially held her back: “I was part of this culture where every race and every sport I had ever participated in had separate gender categories. So I assumed that on a long-trail record it would be the same,” she says.

My grandmother doubled her landscaping goals once I showed up. After being neglected and abused by my mother, part of my healing came from deep within my grandma’s heart, but the other part came from hard physical labor. The fact that I was a girl was, as my grandma would have said, “immaterial.” There was lots of work for me to do, from moving and stacking entire cords of wood and dragging fallen branches deep into the woods to digging holes through packed earth and shoveling the driveway out from under a foot of snow. By the time I was 10, I was doing small engine repair on our old mower, which sometimes cut out as we chugged up a steep hill, leaving me to dig my feet and legs deep to keep it from rolling backwards over my bare feet.

These were early lessons in defining my own strength. But the culture I grew up in still thinks I can’t change the 5-gallon water container in the office. (I can.)

Many women have no idea how physically strong they are. But if men can be just plain strong — parenthood or psychological status aside — science suggests that so can women. I learned this from my grandmother, and from my own body. I can feel it in my muscles.

AKA The Curious Human. Science journalist & nature nerd w/serious wanderlust. Former geologist. Still picks up rocks. Words in @NatGeo @SciAm @Slate @CNN, here.

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