Women-Specific Strategies to Train and Compete in the Heat

Race day temperatures are rising. Here’s what active women need to know.

As I write this, race season is underway in the Northern Hemisphere and temperatures are climbing as much as 20 degrees above average across a large swath of the U.S. As sweltering weather becomes the norm, it’s increasingly important for women to learn how to work with their physiology to keep their cool, stay safe, and perform their best in the heat.

It won’t surprise anyone reading this that women have different needs than men when it comes to training and competing in the heat. For one, research suggests that though both sexes see their core body temperature rise when they get dehydrated during exercise, women’s cores may get hotter at a lower level of dehydration because they start out with a lower volume of body water than men do; and have a more rapid rise of core temperature in the early stages of exercise.

Men also have a higher overall sweating capacity, which appears to be an advantage in hot and dry conditions, where sweat evaporates and helps keep you cool quickly, but a disadvantage in hot and humid conditions, where they end up with what’s called “wasted sweating,” where you’re pouring sweat, but it’s not evaporating or cooling you. Women, who have and use more sweat glands, but generally sweat less and “waste” less sweat, are better equipped to tolerate hot and humid conditions.

And of course, sex hormones matter. In the luteal phase of your cycle, especially when hormones are highest in the week or so before your period, your core temp is slightly elevated; you start sweating later after starting exercise, and your blood plasma volume is reduced by up to 8 percent. This also holds true for the active weeks of contraceptive pills.  That means your tolerance for heat is lower, so you really need to be on your game when it comes to staying hydrated and being sure you’re fully acclimated going in.

Managing hot conditions can be even harder for women in peri and postmenopause because low estrogen can blunt your normal cooling responses during exercise as well as blunt your thirst sensation and sweat rates. Typically, your blood vessels expand as you warm up, sending blood closer to the skin for cooling. With this response dampened, more heat is trapped in your core, so you can feel like you’re burning up and need to slow down when you want to start going hard. Your body’s thermostat is also more likely to overreact to changes in temperature because your sex hormones aren’t there to help regulate it, which means you may be more susceptible to hot flashes, too.

How to Prepare to Beat the Heat

The first step is acclimatization, which is as it sounds--training your body to perform its best in the heat. The goal is to expand plasma volume, increase sweating, and boost vasodilation at your skin, so your body can offload heat as effectively as possible.

Though women and men are equally responsive to heat acclimatization strategies, research shows that females need to do about twice as many heat adaptation sessions (10, as opposed to 5) to get the same magnitude of adaptations as their male peers.

In fact, a 2019 study published in Frontiers of Physiology found that women who followed a 4-day heat training protocol did not show improvements in performance during a 15-minute cycling time trial in a 95 F (35C) environment. However, women who followed a 9-day heat training protocol improved their mean power output by 8 percent, their speed by 3 percent, and went 3 percent farther during the same time trial.

If you’re prepping for a hot event in a cool environment, these steps can help:

• Wear more layers. You can stress your body’s thermoregulation system to kick-start the heat dissipation responses by simply wearing more layers while training. Start by doing a few easy workouts in long sleeves and then work up to adding a cap. Make sure everything is breathable, and don’t overdo it. The goal is simulating a hot environment, not giving yourself a heat illness.
• Apply the sauna protocol. Head into a hot place like a sauna for 25 to 30 minutes after a workout or at the end of the day when you’re already a little dehydrated. The combination of low blood volume and thermal stress triggers a cascade of physiological reactions that help your body cope with heat stress. Again, it takes 9 sessions, so plan accordingly. You’ll want to allow yourself 5 to 6 days for your body to rebound back to full blood volume before your race.

The optimal heat training plan for women is also affected by which hormone phase we're in. In the low hormone phase, which is right before, during, and right after your period, your body needs a 5 to 10-minute “primer” of heat exposure before the full session. So go into the sauna and heat up. Then get out for 5 to 10 minutes before starting your actual session. For women in peri and post menopause, this primer is also needed because of a slower response to the heat. If you're in the high hormone phase, your body has already shifted to a higher thermoregulatory threshold, and no primer is needed.

Hydrate. Hydrate. Hydrate

Hydration is the top priority in hot conditions because the water in your body is how you offload heat. As your blood circulates through your muscles, it delivers oxygen and fuel and picks up and carries out byproducts of energy production, like heat. The blood carries it to the skin where you can get rid of it through a number of cooling mechanisms, including the most efficient–sweating. 

The rub is you lose water from your blood when you sweat, so your plasma volume drops. Unless you take in sufficient fluids, your primary cooling system will be compromised, because you just won’t have enough body water to send to the skin as sweat. 

So staying on top of your hydration is paramount. This can be trickier for women, who are naturally more prone to hyponatremia (a.k.a. “water intoxication” or dangerously low blood sodium). That’s why you may have read that you should always drink according to thirst. Well, that advice isn’t quite adequate for women, because our sex hormones can dampen our drive to drink, especially in the high hormone phase of the menstrual cycle (this can become even more pronounced during perimenopause). Lack of thirst also can get worse with age, and postmenopausal women especially can have low levels of thirst. 

The better solution is to follow some general guidelines to ensure that you’re taking in what you need throughout training and competition. Generally speaking, take in fluids at the rate of 0.12 ounces per pound of body weight (that’s about 17 ounces for a 140-pound woman) per hour in temperatures 75 degrees Fahrenheit and below, and 0.16 ounces per pound of body weight (roughly 22 ounces for that same woman) per hour in temperatures above 80 degrees Fahrenheit to help maintain blood volume. 

Also, skip the salt tablets. You’ll be getting plenty of sodium from your sports drinks and foods. If you take in high doses of sodium, you can end up with reverse water flux, meaning your body water goes toward the sodium in the digestive tract, which can cause GI issues like gut sloshing and dehydration. 

Strategies to Perform and Compete in the Heat

• Keep your cool. Your goal is to start your event with a nice, cool core. Don’t exercise hard, get into a sauna, hang around in the heat, or do anything to drive your core temperature up in the 24 hours before your event.
• Take a dip. Precool your body if possible by immersing yourself in cold water for 10 to 15 minutes. Take a dip in a body of water. Or take a cold shower. It’ll drop your skin and core temperature, so you’re nice and cool for the start.
• Drink a slushy. If possible drink an icy beverage to lower your core temperature and create a heat sink, so you store less heat and store it more slowly. This will help you tolerate a higher core temperature during exertion and push back the onset of heat-induced fatigue. Just be careful to not buy a gas station Slushy that is loaded with sugar. You want a drink that is 3 to 4 percent carbohydrate (i.e. about 7 to 9 grams of carbs per 8 ounces).
• Cool your skin. Cool your skin on the back of your neck and/or forearms with moist towels. Just don’t go too far and try packing yourself in ice. Ice on the skin is too cold and actually constricts your blood vessels, forcing hot blood from the skin to your core, having the opposite effect of what you want!
• Kickstart circulation with beta-alanine. For women in the menopause transition who suffer hot flashes, a dose of beta-alanine, which helps open your blood vessels, before you head out can help ward them off and help your body shuttle blood where it needs to go to keep you cool. The typical recommended dose is 4 to 6 grams. Some people get a pins and needles sensation at the higher end of that recommended dose. You can avoid that by using a sustained release formula or taking a couple of smaller doses.