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Men and women respond to heat — and sweat — in similar ways, study finds

REUTERS/Lucy Nicholson
Emily Infeld reacting after placing third in the women's 10.000m event during the 15th IAAF World Championships in Beijing, China, on August 24, 2015.

The ever-proper Victorians used to say that “horses sweat, men perspire and women glow.”

Since then, we have become less squeamish about using the word sweat, even when talking about women. Yet we still insist that sweating is really more of a male thing. The current assumption (and it’s a longstanding one) is that men sweat more heavily than women due to gender differences in the response of their bodies to warm temperatures or physical exertion.

Well, a new study is calling that assumption into serious question. It has found that heavier sweating is not related to gender, but to body size.

“Gender has long been thought to influence sweating and skin blood flow during heat stress,” said lead author Sean Notley, who is currently a postdoctoral researcher at the University of Ottawa in Canada, in a released statement. “We found that these heat loss responses are, in fact, gender independent during exercise in conditions where the body can successfully regulate its temperature.”

The human body’s “normal” internal temperature tends to range between 97 degrees F and 99 degrees F. When the temperature climbs above that range, the body has two ways of cooling down: by increasing blood circulation to the skin’s surface (where the heat can be lost to the air) and by sweating.

Notley and his colleagues hypothesized that the ratio between body surface area and body mass — not gender — determines how a body responds to a heat challenge. They also hypothesized that larger bodies of both genders would sweat more than smaller bodies as internal temperatures rise.  

Study details

For their study, the researchers recruited 60 young, healthy, physically active students at the University of Wollongong in Australia (where Notley was a graduate student at the time). The participants included 36 men and 24 women of various sizes.

Each student was brought into a lab on two separate occasions, during which they were asked to cycle on a stationary bike at a steady, heat-generating pace (“light” during one session, “moderate” during the next) for 45 minutes. For both sessions, the lab was heated to 82.4 degrees F and had a relative humidity of 36 percent.

The researchers measured the participants’ skin blood flow and sweat as they exercised. They found that the bodies of smaller people — both men and women — relied more on increased blood flow to the skin to cool off. And, as a result, they sweat less.

Specifically, they found that surface-area-to-weight ratios accounted for 10 to 48 percent of individual variability in the heat response of the participants, while gender accounted for no more than 5 percent. 

Limitations and implications

Because of the study’s limitations — particularly its relatively small size, the homogeneity of its participants (all young students) and the use of only one type of heat-inducing situation — these findings are not, necessarily, the final word on this issue.

But if the findings hold, it will lead to the debunking of yet one more gender myth. For, as Notley and his colleagues explain in their paper, although men may — as a group — sweat more than women, they do so because they are typically larger than women.

It’s not because their cooling mechanism is somehow more “efficient,” as has been claimed in the past. 

Women glow? Sure. But, like men, they also sweat — and often just as heavily.

FMI: The study was published in the journal Experimental Physiology, but is, unfortunately, behind a paywall.

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