Intake: Water on the Mountain
By Suzanne Schlosberg

You wouldn't think of going on a three-hour bike ride without a water bottle or two. But get on the ski slope, where your equipment doesn't boast handily mounted water-bottle cages, and a morning can dangerously slip by without proper hydration.

"Cold, dry air is deceptive, because you don't see or feel yourself sweating like you do when you exercise in hot, humid air," says Melinda Roalstad, assistant director of sport science for the U.S. Ski Team. Furthermore, Roalstad explains, because cold air doesn't hold as much water as warm air, your body must rob itself of water to warm the cold air before it gets to your lungs. The result is a fluid deficit that can profoundly affect your stamina.

"Performance starts to decrease when you lose as little as 2 percent of your body weight in water, which is really minimal," Roalstad says. It's not unusual to lose three or four pounds of water in a four-hour session on the snow.

Since thirst is a poor indicator of fluid loss, it's best to carry a water bottle or two in a fanny pack, or wear a backpack-type hydrating system, and partake on every lift ride. Try to down two tall glasses of water at lunch and two more right after skiing. And as for alcohol, be aware of its fluid-depleting diuretic action. Order a water chaser.