I see people walking half a mile holding their water like a lifeline, stopping often to drink from that omnipresent water bottle.
And I say: take it easy.
It's not that people exercising do not need to watch their hydration level. One should be properly hydrated, and we need to drink a certain amount of fluids to keep our bodies healthy. However, people are taking the recommendation to ridiculous lengths.
Physician Heinz Valtin, a kidney specialist and professor emeritus of physiology at Dartmouth Medical School, states that the "8x8" recommendation is a myth.
Now, that doesn't mean that people who exert themselves do not need to remain properly hydrated. What it means is that people need to drink enough. Diuretics (including my personal favorite, iced tea with a little Herman honey) count toward the daily total.
Drink enough to feel sated, and drink regularly enough to avoid feeling dry. But don't go overboard.
How much is enough? According to Greg McMillan, an Arizona exercise physiologist and running coach, a person's urine should be straw-colored ("When the Heat Can’t Be Outrun," (New York Times, October 11, 2007). Drink too little and your urine is much darker; clear urine means you may be drinking too much water. (If your daily vitamins are orange, that will color your perception, so gauge accordingly.)
Too much water can be dangerous: ask the British runner who died in April, or the other 14 people who were hospitalized for the same affliction. Drinking too much water dilutes your body's vital minerals, including sodium, a very important chemical.
Athletes absolutely need to pay attention to their hydration levels. However, don't go crazy. Sports drinks such as Gatorade and Powerade are designed for the professional elite athlete. That means the calories and other essential body chemicals are vastly elevated for the average Joe or Josephine.
Brett Favre needs to down some sport drink after a day's workout because he has worked out his body for an extended period of time. I, on the other hand, don't need to consume that much because the calorie intake will outweigh the rehydration benefits.
Long story short: leave the water bottle at home if you're making a trip to the grocery store. Drink a few glasses of water during the day at work. Drink enough if you're going to work out. However, don't develop a drinking problem.