Sweat might seem like just a sticky issue, but it’s so much more than the reason no one hugs you after a ride. In reality, sweat is your body’s sprinkler system: Heat up enough, and the waterworks activate to help you stay cool and keep hammering down the road. The hotter it gets, the more efficient sweating becomes the key to success. Here’s what you need to know to embrace your natural coolant and make it work for you.
Most of us begin to sweat when our core temperatures rise about 0.3 degrees Celcius above normal, says Dr. Caroline Smith, director of the Thermal and Microvascular Physiology Laboratory at Appalachian State University. As you get fitter, your body becomes more efficient at cooling itself. “Well-trained athletes begin sweating at a lower core temperature, and they sweat more,” Smith says.
Your body also starts sweating nearly immediately when you launch into a sprint or hard effort in the heat, Smith says. In those cases, your body doesn’t even wait to heat up: It knows what’s coming.
You need to drink (almost) as much as you sweat to stay cool.
The human body makes sweat from blood plasma (the watery part of your blood). If you want to keep sweating—and you do—you need to hydrate well enough to prevent your blood from turning to sludge.
How much you need to drink depends on how much you’re pouring out. This amount varies widely from rider to rider depending on a host of factors, including, of course, how hot it is. In one study of 26 cyclists competing in a 164km road race, sweat losses ranged from 4.9 to 12.7 liters. You can’t—and shouldn’t try to—replace every drop of sweat you lose, but you need to stay reasonably hydrated. Research shows that about 20 ounces of fluid an hour does the trick for the average cyclist. Bigger riders may need more, smaller riders may need less, and everyone may need a bit more when it’s really hot. Your thirst is a good guide.
In order to hydrate while exercising, it’s important to drink fluids that contain a little sugar and salt (most sports drinks contain both). Both help pull fluid from your intestines and into your bloodstream more quickly, making fluid readily useable for sweat. Your body also loses electrolytes like salt through sweat while drawing water to the surface of your skin, and the salts need to be replaced.
Women sweat less and usually run hotter.
Women typically sweat less than men. If you’re premenopausal, you also have a higher core body temperature and significantly lower blood plasma volume during the high-hormone days before your period. A little chicken broth, miso soup, or sodium-heavy hydration beverage can help pull the fluid back into your bloodstream where you need it to sweat.
Sweat needs to evaporate to cool you.
Pouring buckets of sweat doesn’t do you much good if it just soaks your clothes and sits on your skin. The cooling response is a result of evaporation, which happens as your body unloads heat energy while helping the sweat turn gaseous. That’s why it often feels harder biking in humid conditions. It’s also why it’s important to wear wicking materials that pull sweat from your skin through the material and into the air.
Train your sweat response.
Just as your sweat rate changes as you get fitter, it also adjusts to heat, says Stanford-based exercise physiologist Dr. Stacy Sims. “As you acclimate to the heat, your total blood volume increases, and your heart rate and body temperature get lower at any given exertion. You start sweating earlier and sweat more, so you can better cool yourself. The composition of your sweat changes, so you lose fewer electrolytes as you sweat. All are key for sustaining exercise in the heat,” she says.
Heading somewhere hot from somewhere not for a big event? Unless you can go ahead of time to acclimate, you can do some DIY heat acclimatization wherever you live. Simply wearing more clothes and using fewer fans on your trainer can help your body prepare for being in a hot environment. Just be sure everything is breathable and don’t overdo it. You want to simulate a hot environment but not give yourself heat illness. You can also use hot yoga or a sauna, says Sims. But you need to be consistent for about five days in a row to get a benefit.
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