How much to drink and when to drink it?  These are some of the most common questions that come to mind in a runner trying to reach an optimal and safe physical performance.  There has been some thought that waiting until feeling thirsty leaves the runner in a bind because it is then “too late” and they have already fallen behind in the race to keep hydrated.  This article will demonstrate that this idea is untrue for most runners.  There have been differing opinions regarding hydration strategies over the years, ranging from fluid restriction to needing to drink before thirst.  In actuality, the ideal method falls somewhere in between and your body is the best hydration “coach”. Thirst is an important way in which our body regulates our fluid status and can be trusted to guide appropriate and healthy hydration, even before, during, and after competition.


Dehydration, in general, does not place a runner into significant risk for serious health complications.  Over-hydration, on the other hand, can put anyone at risk for serious ramifications and even death.  Exercise associated hyponatremia (low blood sodium) is the name of a condition that comes about almost exclusively from over-hydration and can cause a dangerously low level of sodium (an electrolyte) in our blood.  If this is not treated appropriately and promptly, it can result in serious neurological effects and can affect the lungs as well. It has been shown that the electrolytes in sports drinks cannot help prevent this low level of sodium (hyponatremia) as the level of electrolytes is too low; so just switching to sports drinks while still consuming too much fluid, will not prevent the problem and can potentially worsen it.  The only way to prevent exercise-associated hyponatremia is to avoid consuming too much liquid.


Thirst has been defined as a deep urge and desire to seek out water.  This urge is the result of a complex set of mechanisms in our bodies that are finely tuned to protect the hydration status of each individual.  There are receptors in our brains and necks that assess the water-electrolyte balance in our blood, circulating volume of blood, and blood pressure which can trigger a cascade of events to induce the sensation of thirst.  These events occur rapidly and when addressed in a timely fashion will keep the individual at a safe and normal hydration level.


There is a misconception that waiting until the feeling of thirst is present is too late to help stay appropriately hydrated.  This is not true; and trusting the feeling of thirst can help any runner stay out of trouble.  One of the safest hydration strategies before, during and immediately after an event is to drink palatable fluids when thirsty.

Authored by UW Medicine Sports Medicine Physicians
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