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Training in the Heat

By Daniel Scagnelli

As summer approaches, it’s important that you plan and prep appropriately when exercising in the hot and humid conditions.

Your Body’s Response to Exercising in the Heat
Exercising in the heat is an added stress to the body because it is much more difficult for your body to thermo-regulate itself. Your body’s natural response is to cool itself, so naturally you send more blood to the skin to help facilitate the cooling process. However, this takes blood away from the working muscles and vital organs, which causes your heart rate to increase. You will be losing more sweat as a result, so it is important to stay hydrated and maintain electrolyte balance. Humidity further compounds the stress because your sweat doesn’t evaporate, so the cooling process is hampered causing body temperature and heart rates to rise even higher.

Heat Illness and Injury
Failing to plan and prepare for exercise in the heat can be detrimental to your health and performance and may even result in heat related illness, which can be very serious and possibly life threatening. The Mayo Clinic outlines three primary heat illnesses, below, to be aware of.

  • Heat cramps. Heat cramps are painful muscle contractions that mainly affect the calves and quads in multisport, but may also be felt in the hamstrings and even abdominals as a result of poor hydration status and electrolyte imbalance.
  • Heat exhaustion. Heat exhaustion occurs when body temperature rises above 103 degrees and may be associated with nausea, vomiting, headache, fainting, weakness and cold, clammy skin. If left untreated, this can lead to heatstroke.
  • Heatstroke. Heatstroke is a condition that occurs when your body temperature is greater than 104 degrees. Your skin may be hot, but your body may stop sweating to help cool itself. Typical symptoms are confusion and irritability. You need immediate medical attention to prevent brain damage, organ failure or even death as heatstroke can be fatal if left untreated.
  • Hyponatremia. Sweat is made up of fluid and electrolytes, so as you sweat profusely you may also lose large volumes of vital electrolytes, especially sodium. It is important that you replace these electrolytes along with water to help maintain hydration status and essential physiological processes. If you were to simply replace sweat loss with just water you may dilute the blood’s sodium content leading to a condition called hyponatremia, also known as overhydrating. Hyponatremia has detrimental side effects that mimic typical heat related illnesses and can be fatal. Therefore, replacing electrolytes, especially during prolonged efforts and any training sessions during intense heat and humidity, is very important.

Preventing Heat Illness and Injury
There are many steps you can take to prevent yourself from suffering from heat illness making sure that you make the most of your valuable training time. The primary way to mitigate the negative effects of heat training is to let your body acclimate to training in the heat.

As you acclimate to hot environments your body will make noticeable changes. You will begin to sweat sooner, in larger amounts, and you may even notice the content of your sweat changing from an electrolyte/fluid mix to a more fluid-based sweat as your body becomes better at retaining vital electrolytes. You will also become more efficient at moving blood through your body and to the skin for cooling purposes.

Initially, you will need to reduce training intensity/volume by as much as 30 to 40 percent as you begin to acclimate to hot and humid conditions. However, our bodies are amazing physiological specimens and respond very quickly to stimuli. The average person will need to allow for roughly two, maybe even three, weeks of consistent training in hot conditions to fully acclimate. Over that two to three week period of time you can gradually increase your volume and intensity until you are back to your pre-heat training level.

Other steps you can take to have the best workout possible in hot conditions:

  • Choose your exercise time wisely. Try not to exercise during peak heat hours if at all possible.
  • Choose your venue wisely as well. Search for shaded routes when training outside in the heat.
  • Wear loose, moisture-wicking, light-colored clothing to help pull sweat away from the skin.
  • HYDRATE. Be prepared and have water, sports drink and nutrition on hand during workouts.
  • Replenish electrolytes during longer workouts.
  • Cool yourself. Some tried and true options are ice packs, cold towels and cold water.
  • Protect yourself from the sun by wearing sunblock and a hat.
  • Rehydrate and refuel. Begin to rehydrate immediately post workout and take in nutrition to begin the rebuilding and replenishment process.

Exercising in the heat doesn’t have to be as challenging as some people make it. By educating yourself and taking some small precautions like those mentioned above you can have a phenomenal workout regardless of the conditions. Have fun, and enjoy your training!

Daniel Scagnelli, MS, CES, CPT, has been training and competing as an endurance athlete for more six years and now focuses on long-course triathlon events. You can read more about One Step beyond coaches and services as

The views expressed in this article are the opinion of the author and not necessarily the practices of USA Triathlon. Before starting any new diet or exercise program, you should check with your physician and/or coach.