Most triathletes know that carbs stoke the engine. During prolonged exercise, glycogen, a carbohydrate storage form, is broken down, freeing sugar (glucose) molecules that muscle cells then oxidize to produce the energy needed for muscle contraction. But steamy workouts appear to put added strain on this valuable energy source, which means you should have special nutrition for the heat.
Research on endurance performance in the heat has shown that the burn rate for muscle glycogen—a major energy source for high-intensity exercise—is greater when temperatures are higher, especially in people who are not used to working out in hot climates. An increase in body core temperature and a shift in hormone balance might be why we rip through our carb stores quicker when the heat is on.
“Understandably, many athletes focus more on fluids over carbs in the heat, but if you don’t stay on top of your carb needs when exercising in hot conditions it can impact muscle function and lead you to fatigue sooner,” says sports dietitian and Ironman athlete Marni Sumbal, author of Essential Sports Nutrition.
Nutrition for the Heat: Eat Your Carbs
It’s widely believed that we need roughly 30 to 60 grams of carbohydrate per hour of exercise. “I would encourage people to start on the lower end of this range as digestion and absorption of nutrition is compromised in the heat,” Sumbal says. “More frequent, consistent intake is better than consuming your calories all in one shot.” Carbs can come from any combination of sports drinks (4- to 8-percent carb concentration), gels, and foods. Everyone reacts to nutrition differently, so it might take a bit of trial and error to determine what works best for you when pushing the pace in the heat.
Nutrition for the Heat: Chill Out
To help stimulate your appetite, which can take a nosedive during hot workouts, Sumbal suggests doing what you can to turn down the furnace such as using iced towels and cold water to keep the skin cool.
Nutrition for the Heat: Get Salty
The average person has 4 million sweat glands, and when you’re pushing the pace in the heat they are going to be working overtime to balance your body temperature. As a result, you’ll shed more electrolytes, namely sodium chloride (salt) with smaller amounts of potassium, magnesium, and calcium also present in sweat. Essentially, think of your body as a big bag of salty water.
“Electrolytes are necessary for proper muscle contraction and relaxation as well helping you absorb, retain, and distribute the water you drink for better fluid balance,” Sumbal explains. She adds that salt consumption also stimulates thirst, which drives you to drink more and, in turn, maintain better hydration. This requires replenishment, particularly sodium, during hard workouts in the heat. Sumbal says replacing salt becomes more of a concern when you push past the 60-minute mark, particularly if you’re sweating heavily. “Most athletes will sweat out 400 to 1000 milligrams of sodium per hour of activity,” Sumbal says. If you’re exercising in humid climes or genetically sweat a lot, you’ll shed closer to the higher end of this range.
Nutrition for the Heat: Drink Up
If you aren’t drinking enough water to go along with your carbs, you’re setting yourself up for gut rot—issues of bloating, sloshing, and nausea. Sumbal recommends drinking 12 to 16 ounces of liquid every 30 to 40 minutes of exercise in steamy conditions. But not just any liquid. You need electrolytes, remember?
A number of sport nutrition products such as sports drinks and tablets emphasize their enhanced electrolyte content, designed to replace some of what’s lost in sweat and prevent hyponatremia, a dangerous drop in blood sodium levels that can occur when athletes drink plain water to excess.
So you should be looking for a drink that delivers at least 200 milligrams of sodium per 8 ounces, but be careful about downing too much salt in a single shot. “Dumping a bunch of sodium in your body at once can cause fluid retention in the stomach and gut issues,” Sumbal says. As with carbs, she stresses the importance of smaller doses spread out over your workout. And think ahead when you know you’ll be exercising in an intense climate. A study in the journal Medicine and Science in Sports and Exercise found that taking a moderate amount of pre-workout salt (read: not multiple salt pills) can offer a performance benefit for those about to take part in prolonged exercise in a hot environment. So feel free to break out that bag of salty pretzels.
Nutrition for the Heat: Products to Try
These products can help you perform like a champ even when getting roasted.
Gu Roctane Sea Salt Chocolate Gel
Fast-digesting carbs team up with a generous 180mg of sodium in a flavor to appease chocoholics. The gel is perked up with caffeine which may further bolster performance in the heat.
Liquid I.V. Hydration Multiplier
Ranking high on the electrolyte-scale—500 milligrams of sodium and 370 milligrams of potassium in each packet—its unique “Cellular Transport Technology” uses a specific ratio of glucose, while the high electrolyte content allows for faster fluid absorption.
The tasteless capsules contain an electrolyte balance very similar to what is lost via sweat and are independently tested to be free of any “no-no” substances. Pop one or two (not more!) for each hour of sweaty activity.
Bonk Breaker Chews
A super-easy and tasty (read: no overpowering fruity flavor) way to get more carbs into your system to help beat the heat-inducing bonk. Each package of chews also delivers 140mg sodium, the key electrolyte you sweat out. Make sure to chase with water for better digestion and to dislodge some of the calories from between your teeth.
Base Performance Base Hydro
Perfect for athletes out for the sweaty long-haul, this endurance-minded sports drink isn’t stingy with its carbohydrates—21 grams in each scoop—or its sodium, 280mg, which is more than you’ll find in your standard vending machine sports drinks. The use of multiple carb sources promotes improved burning rates and also digestion, so you’re less likely to need to make a port-a-potty run.