Don't let sodium deficiency trip you up on the trail

Tim Hussey

During periods of sustained physical exertion, your body prevents itself from overheating by flushing water through the pores of your skin. The price for keeping cool is that you not only lose enormous amounts of water—up to 25 milliliters each minute—but also significant amounts of salt (hence those unsightly white rings around your armpits after an epic mountain bike ride). The traditional mantra for outdoor enthusiasts—drink water or die—helps you to redress the H₂O deficit, but it does nothing to replace the lost salt, which is critical for transmitting nerve impulses in the brain. Once blood-sodium concentration drops below 9 percent, hyponatremia sets in. The symptoms, which include malaise, confusion, and nausea, can presage severe and in some instances fatal complications.In 1998, Kelly Barret, a 43-year-old distance runner, died while participating in the Chicago Marathon. Although his death was attributed to a rare heart condition, doctors said it was aggravated by hyponatremia. Part of the problem is that in its early stages, hyponatremia mimics heat exhaustion, which makes diagnosis quite difficult. "They look exactly alike," says Collins, "but you treat them differently."

During the last few years, efforts to detect, treat, and prevent hyponatremia have increased significantly. In 1997, Dale Speedy, a University of Auckland physician, conducted the first comprehensive hyponatremia study at the New Zealand Ironman and found the condition in one-fifth of 330 finishers. Those numbers have gone down in the past two years, but cases in noncompetitive outdoor activities have rocketed upward. In 1989, the first hyponatremic hiker was evacuated from the Grand Canyon; by 1999, the number of diagnoses in the park had risen to 36. The elevating statistics led park rangers to pioneer the use of portable blood-chemistry analyzers in 1996, which allow for on-the-spot assessment and treatment. This summer, Collins is trying to add another of those $5,000 analyzers to the three currently in use. She's also expanding the park's Web site to educate visitors about the risks of hyponatremia during desert hiking.

Experts say that prevention hinges on maintaining a consistent water-sodium balance by not drinking too much water and by replenishing at least some of that lost salt. Caveat: Don't overdue it. The simplest remedy is an off-the-shelf sports drink like Gatorade, which is loaded with sodium-rich electrolytes. Or, as Collins points out, Cheez-Its—a prescription that may soon imbue the snack food with a noble new role. "Now," notes Hawaii Ironman medical director Bob Laird, "it can save lives." —CAROL KAUDER

"I felt perfect. Perfect," declares Francisco "Pipin" Ferreras, describing his 531-foot world-record dive off the coast of Cozumel, Mexico, on January 18. Ferreras's single-breath dive—or rather, plummet—to the ocean depths on an 80-pound sled beat out Italian Umberto Pelizzari's previous world-record dive of 492 feet, set last October. After claiming the record on his second attempt (he had passed out while surfacing from his first dive two days earlier), the flamboyant Cuban, who's been profiled in Outside, was serenaded by a strolling mariachi band and presented with a cake by the local mayor. In September he'll try to best himself by pursuing free-diving's Holy Grail, a 656-foot dive that, says Ferreras, could have implications beyond extravagant self-publicity: "I want humanity to know that living inside every human there's an aquatic soul. It's going to give a whole new kind of hope to the world." —STEPHANIE GREGORY