June: Gambler

   You probably know that your feet begin swelling in the morning and continue to engorge throughout the day. Melting may be too strong a word for what's happening, but your body is clearly running downhill-at least the water part is, which, like it or not, is the human being's essential secret sauce. Even your mortal blood is mostly water.

   You'd think runners would have hydrating down. Unfortunately, hot weather and the desire to succeed stir up trouble during races and workouts, turning us all into high-stakes gamblers. Thirst is a slow and imprecise messenger for telling you how much fluid your body needcor how fast you're losing it. Lacking any better information, all of us must place occasional informed wagers on it, even when our health or our lives are part of the ante.

   The amount of water your body needs, for example, changes not only with the weather but with the variable rate your blood bails it through your sweat glands in order to keep your slippery body cool. In the late 1950s, physicians from the U.S. Marine Corps noticed that boot-camp recruits from northern states collapsed from heat exhaustion far more frequently than recruits from southern states. We now know the body adapts to hot climates through exposure over time-decreasing your heart rate and core temperature, increasing your blood volume and sweat output.

   Most of these changes occur in three to five days. If unaccustomed to hot weather, you may need two full weeks to acclimate thoroughly. Place your bets accordingly. The first warm day of the year will tempt you to run inadvisably exuberant distances. If you train in Ottawa or Reykjavfk and plan to run the Maui Marathon, you should arrive several days beforehand.

   The same is true of the water needed to replenish lost fluids before and during a hard run. By the time you're thirsty, your body is already dehydrated. So you'll want to drink well ahead of your thirst. Yet more runners collapse or die from hyponatremia- drinking too much water-than from dehydration. Overhydrated people sweat out the sodium that regulates water balance, cellular metabolism, and muscular contractions. During intense exercise, your kidneys cannot excrete excess water; as a result, your body's cells-including your brain cells, which press against your skull-become engorged.

   To maintain your body's elusive balance of hydration, you must keep up your sodium levels. Sports drinks typically provide 100 to 200mg of sodium per serving - roughly 10 percent of what you'll need for every hour of running. It's better to build sodium levels days before a hot-weather race or workout through meals: salty torlilla chips with salsa, sushi doused in soy sauce, pickles with your tuna mclt, matzo ball soup, kung pao chicken, bacon and eggs. Feast on foods that would make a cardiologist faint.

   Over Lime you'll develop reliable intuition about how your body responds not only to hot weather but to terrain, injury, and the keen desire to win. This intuition lowers the odds that favor the house. It's a gambler's best friend.