How to Push Yourself (Safely) When Exercising in the Heat

Just ask any football player about grueling summer workouts, or those hot August games. While it’s possible to attain peak performance within hot and humid environments, to do so safely, requires adequate hydration and acclimation to heat. This goes for elite athletes, too. No matter what level of fitness you have attained, if you are dehydrated and not used to exercising in the heat, it can be dangerous to train, compete, or race within hot and humid locations. In fact, if you are planning an event, such as a triathlon or a marathon in a location that is much hotter and more humid than where you normally train, it’s time to make a plan. Luckily, there are many strategies to help you hydrate adequately, and to optimize your electrolyte levels.

So why does exercise in hot and humid locations affect everyone, even athletes, so dramatically?

Exercising strenuously in extreme heat can cause hyperthermia; a stressor that impairs physiological and cognitive function and increases the rate of perceived exertion during physical activity. Body temperatures rise quickly, causing you to sweat more when exercising in high heat and high humidity environments. You often become disoriented, nauseous, dizzy, experience cramping in the gut or muscles. In some cases, you might even pass out, vomit, or have heat stroke later in the day. Some people with underlying health conditions such as diabetes, high blood pressure, or asthma can get triggered from the extra exertion and toll on the body and require hospitalization.

Bottom line, it doesn’t matter whether you are in the best shape of your life, training and competing in the heat requires planning to be safe. For instance, if you are dehydrated when you start your training or game, just drinking a bottle of Gatorade during the event won’t be enough and can cause nausea. Knowing how to hydrate adequately is critical to replace electrolytes (sodium especially) and fluids lost, allowing you to perform at peak levels, according to a consensus statement by the International Olympic Committee (IOC). The IOC recommends hydrating before, during, and after exercising in hot environments, to keep cognitive and physical reactions at bay.

“Hydration for performance doesn’t begin when training starts. Staying well hydrated to support optimal performance, especially in the heat, means being intentional about hydration in the hours and even days before training or an event,” says Stephanie Miezin, MS, RD, CSSD Director of Nutrition at Canyon Ranch. Stephanie has extensive experience working with elite athletes. Before coming to Canyon Ranch, she worked for the US Olympic & Paralympic Committees.

Here are her top hydration tips:

• Hydrate throughout each day by drinking, at minimum, half your body weight in ounces per day (75 oz. for a 150 lb. person) mostly from water.

• Salty snacks and high-quality electrolyte powders are your friends. Snack after the event on salty foods, like pretzels and add electrolyte powder to water. Why? Hydration is not just about fluids, but electrolytes too. Electrolytes help us hold on to fluid in the body and support proper muscle function. Sodium is the main electrolyte lost through sweat and so should be the electrolyte with greatest focus on consuming for hydration. Potassium is also lost through sweat, but generally at a much lower rate than sodium.

• In the 2-4 hours before training in the heat, consume between 2-4 ml fluid per pound of body weight. For a 150 lb. person that would be 300-600 ml or 10-20 oz. fluids. Consuming foods, such as pretzels, or fluids, such as a sports drink, that contain sodium during the pre-training timeframe helps with fluid retention to support better hydration going into the activity.

• During exercise hydration needs are unique, but typically 13.5-27 oz. per hour can meet the needs of most people.

• Don’t gulp. During exercise in the heat, sip on fluids frequently rather than gulping large amounts to stay better hydrated and avoid vomiting.

• Avoid flavored, sugary beverages. Instead, consider a drink like water infused with fresh fruit or a sports drink during exercise to encourage drinking enough.

• Colder is better. To support management of core temperature in hot environments, keep your drinks extra cold, or even half frozen like a slushie. Very cold beverages may be able to reduce core temperature in very hot conditions and so support performance.

• Post hydration needs. After exercise, re-establish hydration by drinking 125-150% of fluid deficit (body weight lost during exercise). It is recommended to consume more fluid than the amount lost during exercise to account for the urinary losses that will occur in the post-exercise timeframe.

• Avoid alcohol. To optimize hydration efforts following exercise, it is best to avoid alcohol as it can promote fluid loss through urine.

References Thomas, D. Travis, Erdman, Kelly Anne, Burke, Louis, M. (2016). Nutrition and Athletic 2016 Performance Position Paper. Official Journal of the American College of Sports Medicine, (pgs 543 – 568).

Trangmar, Steven J., Gonzalez-Alonso, Jose. (2019) Heat, Hydration and the Human Brain, Heart and Skeletal Muscles. Journal of Sports Medicine (69-85).

Bergeron, MF, Bahr, R., et al. (2012) International Olympic Committee Consensus Statement on Thermoregulatory and Altitude Challenges for High-Level Athletes. British Journal of Sports Medicine (770-779).