Heat Illness and HydrationheadingContent

Posted on August 03, 2013

woman smiling about to drink water from a bottleThe summer is heating up, but here in South Florida nothing stops our athletes and weekend warriors from getting out, playing sports, and exercising in the beautiful weather. However, with the temperatures and humidity increasing, we must take extra precautions to prevent dehydration and heat illness – which can be devastating, life-threatening injuries. The good news is with some knowledge and common sense, these are preventable injuries.

Water and hydration are important for athletic performance. Research studies have shown that during athletics, people do not drink enough to replace the losses from sweat. Most athletes only replace about two-thirds of their loss when practicing in a hot environment.

Thirst is not a reliable indicator of dehydration, and in fact once you are thirsty, you are already behind in your replacement.


Under prolonged exercise, especially in hot conditions, we may lose two liters of fluid per hour while sweating. This means we may need an additional four liters per day of water to maintain normal fluid balance. Dehydration not only causes poor performance which may lead to injury but has serious consequences when not prevented or treated.


Maintaining good hydration allows us to have a normal sweat response – which keeps the body temperature within a normal range. If we do not replace the electrolytes and water that we lose, our core temperature starts to rise leading to heat illness.

  • With only 1% loss of body weight due to water loss, core temperature starts to rise.
  • When approaching 5%, we see a significant strain on our heart and are unable to lose the heat through sweating.
  • At about 7% loss, athletes may lose consciousness and collapse. It is common for an athlete to lose 2 to 6% body weight of water during athletic performance.


Heat illness is described as heat cramps, heat exhaustion, and heat stroke. When the body reaches a level of heat stroke, with a temperature sometimes as high as 105°F, all body mechanisms of cooling have failed and the sweating mechanisms have shut down. This is an emergency which, if untreated, can lead to death.


We can prevent these heat illnesses by:

  • Maintaining hydration.
    • Fluid replacement has to start before exercise continue during and must continue after exercise.
    • Drink at least 16 ounces of fluid two hours before athletic events, making sure it is not caffeinated.
    • Ideally, during exercise, replace sweat loss as it occurs.
    • Drink 8 ounces every 15 minutes in regular intervals to help replace fluid loss before thirst and dehydration occurs.
    • The ideal drink is ice cold water or commercial sports drinks with electrolytes and low sugar content.
  • Replacing electrolyte losses.
    • By eating well-balanced meals and increasing salt intake before athletic performance, especially in the heat, you can help maintain electrolyte balance.

The bottom line is that when you are dehydrated, your heart works harder, your body temperature increases, strength and endurance decrease, fatigue occurs faster and your mental capacity is reduced.

All of these lead to poor sports performance and potentially life-threatening heat stroke. Other ways to prevent heat illness include wearing lightweight, porous, light-colored clothing and changing your shirt if it becomes soaked in sweat.

Playing sports outside in high humidity in temperatures greater than 82°F has been shown to be a highly dangerous combination.

Parents, educate your children about the importance of paying attention to hydration – especially as the August month approaches and kids return to training camps for school sports such as soccer and football. Simply paying attention to hydration can make sports fun and injury free.