| Family Vacations, Summer 1996|
It's axiomatic that you need to drink water when exercising, particularly outdoors. Still, most people underestimate the amounts of water required for proper hydration--as well as the seriousness of failing to maintain it. Herewith, a crash course in Anatomy 101.
Your body works like a radiator, with blood as the coolant. Blood absorbs heat, the by-product of energy created by muscles, and carries it to the tiny capillaries right beneath the skin's surface, where the heat is transferred out of the body and into the air.
Water is the primary agent for this heat transfer--your blood volume is 70 percent water. In the course of a day, your body uses more than five pints of water simply carrying out this radiator function. When exercising, the body's water needs can double: More energy and, thus, more heat are being generated. During exercise the body also sweats, a more aggressive form of cooling requiring more water still. Add high altitude or warm temperatures and the body's water needs can quadruple.
The first signs that an exercising body isn't getting fluids replenished are dizziness and headaches. Find a cool, shady spot to rest and rehydrate, otherwise these symptoms can escalate into muscle cramps, nausea, and fainting. The worst case is heat stroke, when the body's temperature skyrockets and its cooling system shuts down, risking serious damage to vital organs. Seizures, comas, and even death can result.
The thirst sensation kicks in after the onset of dehydration; if you're thirsty, you're already in water debt. Downing a quart or so of fluid prior to heavy exercise is a good idea-water, fruit juices, and diluted sport drinks work best. Once on the trail, figure that you and your kids will need about one cup of fluid every 15 to 20 minutes.
These are popular hydration systems: Camelback's Thermoback (pack houses a water sac with a straw for sipping on the fly), 817-594-1000. Ultimate Direction's XSpurt (ditto, but more pockets), 800-426-7229. Gregory's Hydro Pocket (fanny pack with bottle-holders), 800-477-3420. Traveling Light's Platypus (a collapsible sac easily tucked into shorts or fanny packs), 510-526-8401.
Copyright 1996, Outside magazine