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Here's How Your "Type" of Sweat Impacts Your Fitness

By studying sweat rate and electrolyte loss in marathoners, researchers are honing in on a biochemical way of determining your fueling needs.

As we inch closer to summer and you take your workouts outside in the heat, you'll sweat a ton—even during a moderately intense session. But endurance athletes like marathoners can lose liters during a race—and its not just sweat soaking their shirts, according to research from Exercise Physiology Laboratory at Camilo José Cela University. 

"We not only lose fluids when we sweat—which can be replaced with beverages—but the levels of several electrolytes that are essential to fluid balance and neuromuscular functioning also decrease—especially sodium," lead study author Beatriz Lara said in a press release.

So what? Losing electrolytes like sodium and potassium can be solved pretty easily, right? You've seen a Gatorade commercial before. Well, researchers say it's not always that simple. 

When you don't replenish excessive electrolyte loss with foods and/or drinks, you can experience a condition called hyponatraemia—a sodium concentration in the blood of less than 135 mmol/L—which, in severe cases, can cause decreased or loss of consciousness, hallucinations, brain herniation, coma, and even death. Scary stuff. 

To see how at-risk marathoners are of coming down with hyponatraemia, the researchers analyzed the electrolytes present in 51 marathon runners' sweat (via patches designed to collect sweat) as well as the concentration of electrolytes in their blood after completing a race. 

The first analysis (of the sweat patches) allowed the researchers to classify runners into three groups depending on their sodium concentrations: runners with 'low-salt' sweat, 'typical' sweaters with a normal amount of sodium in their sweat, and 'salty' sweaters who had an excessive amount of sodium in their sweat.

The second analysis (of the blood samples) led them to this interesting finding: The 'salty' sweaters had lower electrolyte levels in their blood despite having properly rehydrated and consumed the same amount of food with salt as the rest of the runners. 

"Electrolyte concentration in sweat is an essential factor for predicting sodium requirements during sports activities—especially endurance activities such as marathons," Lara explains. If you're a salty sweater, you probably already know it. (If you've ever noticed a gritty salty layer and/or white streaks on you skin or clothes post-run, you're probably considered a particularly "salty" sweater.) If you're unsure, you can find sweat test kits online.

"It is likely that individuals with very salty sweat would benefit from oral supplements, such as salt tablets for instance," Lara suggests. If you're a "typical" sweater, you can probably continue to follow your normal hydration/refueling plan

Maintaining your body's sodium levels will be key for your success—not only in preventing a lapse in performance but for avoiding any associated health complications, too. 

Running Nutrition and Hydration Rules >>>




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