Hydration Science

October 09, 2015

Hydration Science

One of the strangest things I had ever heard was from a friend who told me he doesn’t like to have food or water before or during his 20+ mile long runs. The thought process behind dehydrated, glycogen-depletion runs is that by training one’s body to run without hydration or nutrition, one will be primed to run even faster once water and gels are introduced.

Not only is this approach extremely dangerous, but running while dehydrated can severely limit performance and lead to extreme gastrointestinal distress, especially in hot conditions or during hard workouts. From a cardiovascular perspective, dehydration causes the heart to pump less efficiently. According to a study published in Journal of Strength and Conditioning Research, the loss of 1% body mass via sweat increases heart rate by 3 beats per minute. On a hot day, these small increases in heart rate can add up very quickly, and easily lead to overexertion or heat stroke. The necessity of hydration for your heart is similar to oil for your car. Water primes the cardiac cells to ensure the heart does not have to work too hard to pump blood through the body. Exerting your heart beyond what is necessary can lead to increased fatigue, burn-out, metabolic disorders, and, in some instances, death.

Not worried about your heart? To quantify dehydration in a second manner, athletic performance begins to decline at 2% dehydration. To skip water pre-run is to already limit your performance. A study from Journal of Athletic Training describes a hydration experiment where athletes were asked to run 12k while dehydrated. The dehydrated runners ran 2.5 minutes slower than when they ran they ran the same distance hydrated.

Additionally, from a practical standpoint, there is no good reason to not practice the way you plan to hydrate and eat during a race. Knowing how the consumption of liquids affects your body is extremely important. Drinking too much, or too little, during a race can lead to nausea, hyponatremia, diarrhea, cramps, and bloating. Practicing your plan is the only way to understand exactly when and what to drink on race day.

How much should you be drinking before and during your run? Before you head out the door, you should have 8 -16 oz of liquid, one to two hours before exercise. During your run, your hydration needs can vary based on your own sweat rate, as well as the weather, but a good rule of thumb is to have 3 – 6 oz every 30 minutes. To achieve your hydration goals, a comfortable hydration pack and hydration plan is necessary. Hydration packs are available in all shapes and sizes, and can accommodate any type of run or runner.

When I asked my friend if he truly believed that not eating or drinking while running was going to be beneficial, he was absolutely adamant that it would. He and I recently ran the same marathon and were aiming for similar finish times. Halfway through the race when I passed him, I asked him how he was feeling. I was not at all surprised when he told me he had been throwing up for the last 3 miles, and that the electrolytes he was trying to consume were not sitting well in his stomach. I wound up running my goal time and he ultimately dropped out of the race at mile 16.

Anna Weber

#hydration #hydrationpack #hydrationforrunners #hydrosleeve