The trouble with hydration

Taking in enough fluids these days — especially when you exercise? Of course you are. You probably carry a bottle of water with you whenever you plan on elevating your heart rate. You can't pass a water fountain without taking a sip or two.

Well, you may be taking in too much.

Earlier this year, the American College of Sports Medicine released its revised guidelines on exercise and fluid replacement.

You have to be a scientist to figure them out.

The bottom line, though, is that fluid needs vary from person to person — often dramatically. Sure, you can weigh yourself before and after exercise and adjust your fluid intake during exercise — next time — so your weight remains the same.

That's not appropriate for some people. I've consumed close to two litres of fluids on some long runs and still dropped more than four kilos of body weight. The guidelines say I'm mildly dehydrated because I've dropped more than two per cent of my body weight. My endorphin-pumped brain tells me to reach for a cold beer because I've just finished a great workout.

Last weekend, a study conducted by a British scientist and released just in time for the London marathon, run on an unseasonably warm day, suggested that drinking lots of water won't keep you cool or improve your performance.

The study followed a group of male runners in the Singapore Army Half Marathon. The night before the race, they swallowed "telemetric temperature sensors" which allowed researchers to record their internal body temperatures.

What they found was that there was no connection between the amount of fluid each runner consumed, his body temperature and overall performance in the race. The guy who replaced the most fluid lost through sweat — the least dehydrated runner — recorded the highest internal body temperature.

Gets you thinking — how much fluid do we really need?

The old adage of drinking eight glasses of water a day seems to be an urban legend. A study several years ago found there was no scientific evidence for our need to drink eight glasses of water a day. The study suggested that most of us get most the fluid we need from the food we eat. It also concluded that fluids like coffee and beer provide us with some of our water needs — their diuretic properties are exaggerated.

That got me thinking — maybe it wouldn't have hurt to take up that spectator's offer of a beer at mile 25 in Boston last week.