Why Athletes are at Risk for Dehydration and Hyponatremia

We are living in a time of ultra-endurance runs, extreme obstacle courses, and even hours of hard work in the heat putting us at risk for dehydration and even worse, hyponatremia. Both can be harmful to our body and require immediate attention to avoid a trip to the emergency room. What is the difference between dehydration and hyponatremia and how can they be avoided?

Our Body Needs Water and Salt

Excessive Sweating
Sweating Can Lead to Dehydration and Hyponatremia. Predrag Vuckovic E+/Getty Images

The importance of fluid intake and electrolyte balance are important for our bodies to function right. When physical demands like exercise are placed on the body, we begin losing sweat and salt and depending on the length of workout, environment, and even clothing worn makes replacing water and salt (sodium) even more important. When water and salt levels are out of balance in the body, we are unable to function at optimal fitness levels. Excessive sweating and electrolyte loss can lead to dehydration and drinking too much water to fix that problem can lead to hyponatremia which is low sodium in the blood stream. Appropriate applications of both fluid and salt replacement need to happen in order to maintain a healthy balance and endurance athletes especially fight for this stability with every event.

What is Dehydration?

Stay Hydrated
It's Important to Stay Hydrated During Exercise. wundervisuals E+/Getty Images

Dehydration occurs when there is not enough fluid or salts to maintain healthy body processes. Basically, more fluid is lost than is taken in and can lead to negative side effects. During exercise, the body produces sweat which also contains salt or sodium to cool down the core temperature. Excessive amounts of fluid and salt can be lost during this process and the first indicators of dehydration begin with thirst signals. Other signs of dehydration include decreased energy, muscle cramps, heat exhaustion or stroke, and the inability to regulate body temperature. According to the American College of Sports Medicine, sports beverages may be helpful to accelerate rehydration, drinking 3-8 ounces of water every 15 minutes during exercise, and drinking 20-24 ounces of water for every pound of bodyweight lost during exercise within 2-hours of the workout are all great ways to avoid dehydration.

What is Hyponatremia?

Sport Drinks Can Prevent Hyponatremia
Sports Drinks Containing Sodium Can Reduce Risk of Hyponatremia. :PhotoAlto/Sandro Di Carlo Darsa PhotoAlto Agency RF Collecti/Getty Images

Hyponatremia occurs when there is not enough sodium in the blood and this can happen when an endurance athlete drinks lots of water but fails to include any salt replacement for essential electrolyte balance. When we are running long races and even working prolonged physical hours in the heat we are constantly sweating losing precious water and salt. Our sweat contains a good amount of salt and depending on how much we are perspiring and length of exercise event, we can lose 1 liter of water and up to 41 grams of salt. If we fail to replace the salt component and only drink water in these conditions, an over-hydration of the blood can lead to hyponatremia.

Symptoms of hyponatremia range from nausea and confusion to more severe side effects that may include seizure and coma becoming a medical emergency. According to the British Journal of Sports Medicine exercise induced hyponatremia “is likely to develop from fluid overload during prolonged exercise.” In order to reduce the risk of hyponatremia, it is advised to use “replacement fluids of high sodium concentration.” What to take from this article is fluid loss from extended exercise requires both replacement of water but also electrolytes like sodium or salt to maintain optimal body functioning and fitness.


Rice Research University, Salt and the ultraendurance athlete, Sports Med Web, 1997

Rice Research University, HYPONATREMIA AND EXERCISE, PART 2 – MECHANISMS, Sports Med Web, 1997

British Journal of Sports Medicine, Effects of different sodium concentrations in replacement fluids during prolonged exercise in women, Twerenbold R et al., 8/03

Sports Medicine, Fluid and electrolyte balance in ultra-endurance sport, Rehrer NJ, 10/01

American College of Sports Medicine, Selecting and Effectively Using Hydration for Fitness, y Michael R. Simpson, D.O., M.S et al., 2011

Continue Reading