The Secrets of Sweat and Stamina

No one wants to be the sweatiest one in the room. In my adolescence, I brought a back-up shirt to school out of fear of pit stains. However, when you’re an athlete on the starting line, sweat could give you an edge.

Sweating is an inevitable, unpleasant yet crucial part of exercising and performance, but many athletes underestimate its importance. The composition of your sweat is highly personal and can have a huge effect on your ability to race and train. Sweat a lot and you likely need more water per hour than the athlete next to you. End every run with salt stains lining your baseball cap? You’ll likely need to run with an electrolyte drink and it would be a good idea to lube up before your next race to avoid salt-induced chafing.

Here’s everything you need to know about sweat and how to use it to perform at your best.

The Basics

Is it good to sweat a lot when you run? Let’s look at what’s in sweat.

We hear a lot about electrolytes like potassium, calcium and magnesium, but sodium is the one to keep in mind when we’re talking about sweat and athletic performance. The average person’s sweat contains only 150 mg of potassium per liter while sodium can account for up to 2,000 mg per liter. While other electrolytes are essential for maintaining general health, you lose substantially more sodium than anything else during physical activity. That can have a big impact on performance.

Sweat And performance

So are you sweating too much? Let’s look at the science.

The moisture content of sweat comes from blood plasma, so as you sweat your blood volume gradually reduces. The result is a constant cycle of moisture evaporating from your skin. That’s great for regulating temperature during exercise, but only for so long. A lower blood volume means your cardiovascular system has to work harder to pump enough oxygenated blood to your working muscles. It will also eventually become more difficult for your skin to cool your body down.

Sodium helps maintain your blood plasma volume by signaling to your kidneys to retain more of the fluid you consume. Unfortunately, your body can’t make or store much sodium, so you need to replenish it through your diet, or if you’re sweating often or for prolonged periods, through your preferred means of supplementation. Sports drinks and salt pills are two popular ways to replenish sodium during exercise.

The rate at which you lose sodium isn’t just determined by how much you sweat. It also depends on how much sodium you’re losing in every drop. An athlete’s sweat profile is as unique as their fingerprint and can fluctuate with diet, acclimatization to heat, severe dehydration and other factors. But when an athlete figures out their sodium needs during exercise and how it fluctuates, it can have a huge impact on race performance.

A recent study found that athletes who adequately replaced the sodium lost in their sweat finished a middle distance triathlon an average of 26 minutes faster than those who didn’t.

Water Isn’t Always the Answer

Drinking water in a race situation is necessary, but if you don’t replace the sodium you’re losing through your sweat (especially if you’re sweating heavily for prolonged periods of time), you risk further diluting your blood’s sodium levels.

When sodium levels drop too low, it’s called hyponatremia—and it can be dangerous. Symptoms include headaches, fatigue, nausea and vomiting. In extreme cases, it can lead to seizures, coma and even death. To prevent hyponatremia, supplement your fluid intake with electrolytes to balance the sodium you’re losing through sweat.

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