Why Women Might Need Different Hydration Tips

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The average man carries around 44 liters of water, or nearly 100 pounds, hidden inside his cells and filling the spaces between them, or flowing through his blood vessels. The average woman, on the other hand, only carries 31 liters. Even if we consider that women are generally shorter than men, the difference persists: the weight of men is about 58 percent water, that of women is 49 percent. This is mainly because men have more muscle, which holds more water than fatty tissue.

The difficult question, and one that a recent review in the Journal of Applied Physiology is struggling with, is whether it makes a difference in how men and women respond to exercise-induced dehydration. To jump straight to the punchline, the answer is, we’re not sure yet, as most of the research on dehydration has been done on men. But the authors – Kate Wickham and Stephen Cheung of Brock University, Devin McCarthy of McMaster University and Lawrence Spriet of the University of Guelph – claim that there is enough evidence that we cannot just assume that it there are no differences. Research needs to be done.

For starters, it should be noted that not everyone agrees with the premise that dehydration is a serious problem for athletes or sportspeople, regardless of gender. In fact, one of the authors of the new review, Cheung, did a stylish study in 2015 in which cyclists were rehydrated (or, in the control group, not) with an intravenous drip inserted into their arms, so that They didn’t know if they were dehydrated or not. Under these circumstances, Cheung found that even sweating three percent of your starting weight does not hamper performance. It’s certainly clear (at least from my reading of the research) that leaving yourself severely dehydrated will ultimately hurt performance. However, it is less clear that you need to do something other than drink when you are thirsty to avoid these problems.

There isn’t much research directly comparing the dehydration responses of men and women, so Wickham and his colleagues have found pairs of studies that subject groups of men or women to similar protocols in order to compare. the results. One of the trends observed was that the core temperature seemed to rise earlier in women than in men. For example, during a 120-minute cycle race, the core temperature began to rise after 30 minutes in women, by which time they had lost only 0.5% of their starting weight. In men, the temperature began to rise only after 60 minutes and a weight loss of 1.5%.

One possible explanation for this observation is that women, with less water in their body initially, are more sensitive to small sweat losses. It’s not straightforward, however, as you can compensate for sweat loss by moving fluids from other parts of the body to keep your blood volume stable. This is because in cycling studies, women sweated a greater percentage of their body mass, but their blood plasma volume decreased by a similar amount to that of men.

There are also differences in the way men and women sweat. Women tend to have smaller, less sensitive sweat glands with a lower peak flow than male glands. To compensate, they have more sweat glands overall, which interestingly may explain why studies have shown that women have “a more even distribution of sweat all over their body than men during exercise.” Overall, women sweat less than men, which may explain why they have a faster initial rise in core temperature when they start to exercise. And other factors can influence the sweat response, including levels of female sex hormones throughout the menstrual cycle, which can also affect core temperature, fluid retention, and other factors contributing to the condition. hydration.

On that note, it’s worth revisiting an article I wrote last year, on a major meta-analysis by researchers Kelly McNulty and Kirsty Elliott-Sale on the effects of the menstrual cycle on physical performance. On this subject, too, there were a bunch of suggestive but inconclusive results hinting at possible hormone-dependent differences. The question is: what do you do with these clues? One school of thought is that it changes everything. As a performance specialist recently tweeted, “If a coach / trainer doesn’t know the menstrual cycle of their female athletes, they aren’t training them effectively. But that’s not where McNulty and Sale get off: both recently pushed back against this global approach, in favor of personalized advice. For some women, they pointed out, the menstrual cycle doesn’t seem to make a difference in their performance, so why add an extra layer of stress and complexity to their training?

This is a caveat that I would apply to the issue of gender-specific hydration tips as well. Wickham and colleagues conclude with a series of questions that future research will need to answer, such as whether women really start to warm up faster in response to exercise. Until those questions are answered, let’s hope the Twittersphere doesn’t start posting tips on how women should stay hydrated. And even after the research is done, keep in mind that the difference between the average man and the average woman is probably much more subtle than, say, the difference between me and Haile Gebrselassie, whose sweat rate is 3, 6 L / h was one of the highest ever measured. I would say the best advice is the easiest no matter who you are: if you’re thirsty, drink.

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