By Registered Dietitian
on October 09, 2008
Maintaining proper fluid balance is essential for every athlete since small levels of dehydration can negatively impact performance. Not getting enough fluids, high humidity or environmental temperature can interfere with the body’s ability to maintain a normal temperature. It’s very important to be able to recognize the signs and symptoms of dehydration to prevent illness and injury. More...
By dotFIT experts
on October 03, 2008
Maintaining proper fluid balance is essential for every athlete since small levels of dehydration can negatively impact performance. More...
By Registered Dietitian
on October 09, 2008
Optimal athletic performance requires food and nutrient intake that is tailored to each athlete’s sport, training schedule and individual needs. The basics of performance nutrition are discussed here to help maximize your physical potential and reach your performance goals. More...

Heat, Hyponatremia and Hydration

Heat, Hyponatremia and Hydration
Are you properly prepared so your training is safe and your ability to perform in the heat secure? Let’s make sure…

Heat & Hydration
Elite, professional and seasoned amateur athletes generally have no trouble with properly hydrating (maintaining essential body fluid levels) under any conditions. They are keenly aware of the role fluids play in their performance and therefore take the necessary measures to insure proper hydration before, during and after activities, including acclimating (getting used to or adapting) to the environment in which they will be competing.

Heat acclimatization

Exercising in a hot environment accelerates muscle fatigue, and for all the right reasons – it keeps you from training until your body overheats to a point of complete collapse. The negative effects to performance brought on by high temperatures are most profound in the first days of training in the heat. The good news is that almost a complete adaptation can take place in approximately 7-14 days.

The basic ways the body dissipates or drives off heat are: 1) increasing skin blood flow, which moves core heat to the skin, and 2) producing sweat, moving heat to the environment. Both heat loss functions are enhanced during the acclimation period, allowing most athletes to perform at their maximum if they maintain proper hydration. But this can be a challenge. For example, exercising in high heat can increase sweat rates up to three-fold causing some athletes to lose two to three liters of fluids in one hour, which complicates the hydration strategy for maximizing performance.

Fluids and performance
If you are not properly hydrated, you will not perform to potential, even if exercise is only a few minutes long. So obviously, the longer the task the greater decrease one will experience in performance when fluid levels are inadequate. Also, it is important to realize that performance is negatively affected before thirst is triggered.

In case you are wondering how performance is impaired by small fluid deficits, part of it is probably the decrease in plasma volume. Since that’s how we deliver oxygen to the working muscles, any reduction would hamper performance. Additionally, when we lose fluids, especially during exercise, we also lose electrolytes that are involved in muscle and nerve function and use glycogen, the body’s fuel. Therefore, proper intake of all three is the general formula for maintaining proper hydration for extended periods.

Too much of anything can be bad for you
Some people, especially beginner or novice exercisers, have been known to abuse water intake. In their defense it’s usually based on bad or incomplete advice. Inexperienced runners, for example, often function under the outdated notion that you can’t get too much water. Yet they move slowly enough during events to become overloaded with fluid, which can cause hyponatremia.

Hyponatremia occurs when blood sodium concentration falls to an abnormally low level causing a rapid swelling of the brain that can result in seizures, coma and death. The key risk factor is excessive drinking—especially non-electrolyte fluids such as many types of water.

The risk of hyponatremia can be reduced by making certain that fluid intake does not exceed sweat loss and by ingesting sodium-containing beverages or foods to help replace the sodium lost in sweat. Follow the proper hydration instructions for before, during and after training, including weighing yourself after the workout/event and make adjustments appropriately. Additionally, athletes not attempting weight loss can weigh each morning; a stable weight generally indicates proper fluid balance.

Important Guidelines for Parents and Coaches

  • It is imperative that you take the time to ensure your athlete drinks enough fluid before AND after events.
  • Two hours before games and practices, give your child a container with 16 to 24 ounces of fluid. Check to make sure they drank the entire container. Follow the post-exercise guidelines below.
  • This is especially important when it’s hot or humid outside to prevent heat-illness.


  • Make it your policy that water be available during practices and within reason. If feasible, allow kids to drink at will. Otherwise take regular water breaks.
  • For the very young athlete, assign coaches to make sure every kid is getting water during water breaks.
  • Athletes, especially younger ones should be able to drink water every time they request.
  • Train every coach and staff member to adhere to this policy.
  • Learn the signs and symptoms of dehydration and monitor your athletes closely. These include
    • Thirst
    • Dry mouth/cotton  mouth
    • Headaches or lightheadedness
    • Fatigue or weakness
    • Muscle cramps
    • Nausea and vomiting
    • Flushing (red) skin
    • Dry skin (sweating stops)
    • Rapid breathing
    • Increased heart rate
    • Dark yellow (concentrated) urine

General Fluid Requirements

  • Fluids should be cold, palatable and selected based on the type and duration of the activity.   
  • Sports drinks should contain four to eight percent carbohydrate. Drinks greater than 10 percent carbohydrate may slow stomach emptying, cause abdominal cramping and impair performance.
  • Drinks with a combination of glucose, glucose polymers and fructose may enhance water absorption.
  • Solutions containing primarily fructose can cause an upset stomach and should be avoided.  Be sure to check the food label for ingredients.

Pre-exercise Guidelines
  • Drink approximately 16 to 24 ounces of fluid two hours before activity.
  • On warm or humid days, drink an additional eight to 16 ounces 30 to 60 minutes before activity.
  • Water is adequate for activities less than an hour as long as meals are consumed regularly.
  • For endurance events, training sessions longer than 60 minutes, or multiple practices a day, choose a sport drink containing four to eight percent carbohydrate (e.g. Gatorade).
  • For early morning workouts, a liquid meal replacement can be consumed 10 to 40 minutes before activity because it can be rapidly digested.

During Exercise
  • Depending on your sport, consume three to six fluid ounces of water or sports drink every 15 minutes.  This equates to approximately 32 ounces per hour.
  • For prolonged exercise greater than 60 minutes, choose a sports drink with small amounts of electrolytes.

Post-exercise Guidelines
  • Immediately following activity, drink at least 16 to 20 ounces of fluid for every pound of weight lost to ensure proper rehydration. Supervise your youth athletes to ensure they drink the entire amount of fluid you provide.
  • A liquid shake with high carbohydrate content, minimal protein and fat can refuel energy stores and maximize recovery after demanding training bouts. Consume this as soon as possible after workouts or events. The dotFIT FirstString™ Powder meets the NCAA guidelines and is ideal for youth and college athletes.
  • Drink an additional 16 ounces with your post workout meal. This meal should be consumed within two hours after activity.
  • Weigh yourself each morning.  A fairly stable weight generally indicates proper fluid balance.

  1. Bar-Or O. Temperature regulation during exercise in children and adolescents. In: Gisolfi CV, Lamb DR, eds. Perspectives in exercise science and sports medicine: youth, exercise, and sport. Carmel, IN: Benchmark Press, 1989:335
  2. American Academy of Pediatrics. Climatic heat stress and the exercising child and adolescent. Pediatrics 2000;106:158
  3. American College of Sports Medicine, Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007 Feb;39(2):377-90. Review.

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