Most runners and active people have heard the phrase, “you must drink fluids,” repeatedly as the summer months approach. Well duh, who doesn’t drink when it’s hot?
Instead of writing yet another “news flash” article about how you need to drink more in the summer, I’m going delve into some of the specifics of summer hydration – when you should be drinking water and when you should be drinking sports drinks (or an electrolyte beverage) and how to calculate exactly how much fluid you need.
Fluid absorption rate
The critical factor in hydration is how rapidly fluids can be absorbed into the blood stream. The absorption of fluids into the body is largely dependent upon the composition of the fluid in terms of its carbohydrate (sugar), and electrolyte, specifically sodium and potassium, concentrations.
As a general rule, the higher the carbohydrate content of your beverage, the slower the absorption rate will be. Therefore, your choice for hydration will depend on whether your primary aim is rehydration (keeping the body cool and maintaining fluid balance) or the replenishment of energy (sugars and electrolyte stores).
What is best to drink before exercise
Before and during exercise, rehydration should be your main priority. Specifically, when training or racing in warm conditions, rehydration will allow you to maintain fluid balance and stay cool.
Accordingly, your best choice before and during exercise would be water, a heavily diluted sports beverage like Gatorade, or water with electrolyte tablets.
Because of the high sugar content of most sports drinks, the fluid is not readily absorbed into the blood stream. By drinking water alone, diluting your sports drink, or using electrolyte replacements, you provide your body with the best combination of electrolyte replacement and immediate absorption.
Furthermore, sports drinks like Gatorade also contain large amounts of simple sugar. Not only do you want to avoid consuming unnecessary amounts of simple sugar, research shows that when a runner consumes high-glycemic (Gl) foods, like high-sugar sports drinks or energy bars an hour before a run, he or she may become fatigued more quickly.
What to drink after exercise
After you are finished working out, water or a diluted sports drink is not the best choice for your recovery needs. Water and diluted drinks do not contain enough of the sugars and electrolytes that your body needs in order to bring itself back into balance.
In addition, because water or highly diluted drinks are rapidly absorbed into the blood stream, consuming high quantities results in a rise in plasma volume (in non technical terms, this means your body is now over saturated with water). This rapid absorption leads to a further imbalance of electrolytes and frequent bathroom stops, which will only increase fluid loss and decrease your desire to drink.
Your best choice post workout is a drink that contains a fair amount of sugars, electrolytes and possibly some protein. Scientific literature has consistently shown that drinking a beverage that contains a 4 to 1 ratio of carbohydrates to protein is optimal for recovery. Therefore, at the very least, you should be drinking a sports drink after you exercise to help ignite the recovery process.
Calculating your sweat loss for optimal hydration
The most efficient way to rehydrate properly is to put back exactly how much fluid you’ve lost while running. The Internet is filled with general advice on how much you need to drink in order to accomplish this goal: drink to thirst, which doesn’t keep up with the body’s sweat loss rate,; or 8-10oz per hour, which doesn’t factor in temperature or individual sweat rates.
This sounds like a terrible predicament, but calculating your exact fluid loss in any given temperature and humidity is actually quite easy if you use this sweat loss calculator. All you need to input is your weight before each run, your weight after each run, any fluid taken in during your run, and the distance/time you ran. The calculator will do the hard work for you.
Use this calculator a few times in different temperatures and you’ll have an easy reference chart for exactly how much fluid you need replenish on any given run and in any given temperature.
Now how’s that for some practical and useful information for exercising safely this summer!
Jeff Gaudette is a 2:22 marathoner and owner of RunnersConnect, a team of expert coaches and passionate runners dedicated to improving your training and helping you run faster. *He recently released an eBook: *16 weeks to a Marathon PR;* which, if this post is anything to judge by, is pretty darned comprehensive. Download it for free now!*