Sweating the Details

Hydration tips to improve your workout

Dehydration Makes You Suck at Everything

Water is a multitasker: Among other things, it lubes your muscles, transports nutrients around your system, and shuttles waste out of it, allowing your kidneys to function smoothly. Every sweat bead on your skin equals less water in your system. When you've sweated out 1 percent of your body weight, two things happen (and continue to happen with every additional 1 percent lost): Your heart rate rises 7 beats per minute in order to push your thickening blood through your body, and your core temperature increases a third of one degree.

Lose 2 percent, and not only are you physically suffering (your pace slows), but your brain starts going blotto — it's 80 percent water, so it short-circuits at the first sign of a drought. (Maybe that's why I wasn't worried about hydration; I was delusional.) Your reaction times become longer and you have trouble finessing certain tasks, like dribbling or steering. Dry out even more, and you may get headaches, cramps, and dizziness as your body loses its ability to transport blood as efficiently. Lose 15 percent of your body weight and you should start praying like a Catholic schoolgirl during finals: Your body is too dried out to stay alive.

Chugging Is for Frat Boys

Regardless of what's in your water bottle, resist the urge to gulp it all down the instant your workout ends. In fact, sip no more than 16 ounces an hour. If you try to drink more than that after exercise, you'll be lulled into a false sense of security. "Your system can't process bottles of water rapidly," Coyle explains. "Your urine will be clear long before you're hydrated." In other words, you'll be glued to the toilet but won't necessarily get the benefits of whatever you drank. If you plan to exercise twice in one day, the ACSM recommends drinking about 20 to 24 ounces for every pound lost to compensate for the extra urine you'll produce. But for your average day with one hour-long gym session, drinking 16 ounces per pound lost over the day is sufficient.

There's No Perfect Pour

The weather (or lack thereof, if you're a gym rat) and your intensity influence more than anything how much you sweat. And as temps shift, so does the need to pay attention to hydration. One study by the U.S. Army Research Institute of Environmental Medicine and published in the Journal of Applied Physiology found that a 3 percent drop in cyclists' body weight reduced performance by a substantial 8 percent when it was 68 degrees but hardly affected them at 36 degrees.

Clothing matters too. The main function of sweat is to work as your personal AC: When your sweat hits the air, it evaporates and keeps you cool. Wicking fabrics, like polyester and other fancy lab-brewed materials, pull sweat away from the skin and dry quickly, allowing your system to work even more efficiently than Ma Nature engineered. Although studies have proven that wearing cotton — which, when wet, forms a barrier between your skin and the air — doesn't increase your core temperature, wearing it during intense exercise in cold weather, like snowshoeing, does put you at greater risk for hypothermia.

How often you hit the treadmill — or pavement or bike trail — also determines your sweat potential. "It sounds counterintuitive, but the fitter you are, the sooner your body begins to sweat, so a person who's in extremely good shape will produce more sweat than somebody who isn't," says Beth Stover, M.S., C.S.C.S., a senior scientist at the Gatorade Sports Science Institute in Barrington, Illinois. "With each workout, you become a more and more efficient sweating machine."

I Sweat Like a Dude

Ask any unlucky soul who has mopped down a treadmill after a bare-chested man strutted his stuff: Guys pour it on more than women. University of Texas researchers studied 132 triathletes and found that women lost an average of 1.2 liters an hour during moderate-intensity exercise in a warm environment, while men pumped out 1.6 liters. (Yes, people, I dumped 0.1 liter more than the average man, but I'm also not an average woman: I'm 6-foot-3 and weigh 175 pounds.)

Hit the Bottle ASAP if...

... two of these factors are apparent:

1. You can see your pee: If it's dark yellow in the morning, or you're peeing less than once every 4 hours, you need to drink. Also, a properly hydrated person should pee once a night.

2. You feel thirsty: Okay, duh. But the must-drink-now urge doesn't kick in until you're already drying up.

3. You're losing weight. If you lose more than 1 percent of your weight — but are still eating your normal amount of chow — every day for 3 or more days, you may be dehydrated.

Tags: hydration

Issue date: November 2007

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