The science of sweat: hydrating during exercise at altitude

You didn’t swallow any cotton and it’s not the drier air. You didn’t go on an apple juice binge. And you’ve been in the mountains long enough to know that you don’t have altitude sickness. So why do you feel like you’re underperforming as you exercise?

You know some of the performance warning signs. You’re an 8:30 am to 4 pm kinda guy on your skis but you’re ready to call it quits at lunch (and no, it’s not a food coma from an Epic Burger and Two Elk bar). Your runs are slow even though you feel fast. You’re huffing and puffing after a hike that you could complete in your sleep. You’re putting pedal to the metal yet your power wattage is low while your heart is racing. What can keep you from crashing? You need to hydrate.

The National Institutes of Health said it best: “Water is the most important, yet overlooked, nutrient for athletes.” Based on personal experience, I’d believe them. I’ve cramped on a run, sweat through all my energy stores on the bike, had a killer headache and cramped during a swim, had so much cotton mouth while skiing that I stopped counting. It’s not pretty. If only I had more sense to do something as simple as drink more water than what I was having, which was probably only enough to moisten my mouth.

But that doesn’t mean you have to falter like I did. Here’s why you want to hydrate especially while exercising and especially in the mountains:

• You sweat when you exercise—even if you can’t tell like while you’re swimming. You need to replace those fluids that you’re losing through sweat.
• At altitude, you’ll find lower air pressure and less humid air, both of which make you lose water faster from your skin and breath.
• These higher elevations make your heart work harder to pump blood through your body.
• Higher elevations also throw off your sweat rate because you’re breathing harder and faster.
• Sweat enough and your muscles will have a hard time getting the oxygen and nutrients they need from your blood to function properly.
• Data shows that athletes can lose 230-1610 mg/L of sodium through sweat. You don’t want to deplete those electrolytes, which you can replenish with sports drinks.
• You can lose between 27.4 and 47.3 ounces per hour during exercise. That would explain why it’s suggested to drink five 20-ounce water bottles per day.
• Dehydration can be the culprit behind heat-related illnesses, which are more prevalent as the temperatures heat up.
• A lack of fluids can mean less frequent trips to the bathroom and darker colored urine, but you want the exact opposite.
• Even if you’re not thirsty, you still want to drink. One tip ingrained in my brain is that you’re already dehydrated when you’re ready to quench your thirst.

Do you really want your performance to decrease simply because you couldn’t replenish your fluids or you were running on empty? I didn’t think so. Talk about squashing a mountain adventure, and who’d want that?

--Kate Bongiovanni

Photo credit: lululemon athletica