There’s no doubt that working out in the heat can be rough. But if you find yourself on a major struggle bus—maybe you’re cramping, nauseated, or super fatigued—you might just not be drinking enough. “People who are adamantly like, ‘Oh, no, no, no, I can’t train in the heat, I feel horrible,’ that, to me, is a huge red flag of not doing hydration right,” sports dietitian Meghann Featherstun, RD, CSSD, owner of Featherstone Nutrition, tells SELF.
In news to no one, we sweat a lot more when it’s stinking hot out, meaning the risk of dehydration is higher. And that can make a massive difference in how our workouts feel. “Your organs and your cells need water to properly function,” Monique Marcelino, MS, director of athlete research at the University of Connecticut’s Korey Stringer Institute, who studies thermoregulation, tells SELF. In particular, we need enough fluid for our blood to simultaneously deliver oxygen to our muscles and to go to our skin to cool us off. Losing blood volume through sweat makes both of these tasks harder. “So as we get dehydrated, our core body temperature rises faster and our heart rate rises faster,” Featherstun says.
This increases the risk of heat illnesses like heat exhaustion or heat stroke. Plus, all it takes is losing 2% of your body weight for your athletic performance to do a nosedive. It’ll feel harder to hit the same paces. Your muscles might cramp and your GI tract could rebel (think: nausea, vomiting, diarrhea). You may get lightheaded, dizzy, or even a bit confused.
So what can you do to avoid this fate during the next heat wave? SELF touched base with hydration experts and sports dietitians to find out.
Play the preventive game.
Setting yourself up well before your workout is huge. That’s why the American College of Sports Medicine recommends getting in about 5 to 7 milliliters of fluid per kilogram of body weight (or about .1 ounces per pound) at least four hours before heading out in the heat, if possible. Yes, coffee can count toward that, Featherstun says, though Marcelino suggests also having some plain water, too, since caffeine can have a bit of a diuretic effect.
Going into your workout properly hydrated will give you a head start on avoiding that increased heart rate and core body temp, Floris Wardenaar, PhD, an associate professor of nutrition at the Arizona State University’s College of Health Solutions who studies hydration, tells SELF. Plus, you’ll just feel better. “Being good and well-hydrated during the day is good preparation before even starting your workout,” he says.
Drink up during—and let an at-home science experiment guide you to how much.
Just sipping water whenever you feel thirsty isn’t the best way to stay hydrated when you’re sweating through a toasty HIIT session or long run. “If you feel thirsty, that means that you are already on the way to getting dehydrated,” Marcelino says.