From the January 2013 issue of Runner’s World

3 tips for managing your water intake on the run

By Dr Jonathan Dugas

People often blame dehydration for slipping off pace and missing their target digits, and loss of fluids may be partly to blame. But probably much less than you think. You may be surprised to hear that being ‘dehydrated’ doesn’t mean quite what you think it means, and the importance of hydration is often overstated. Here’s how to manage your personal water table on the long run.

1 Respond To Your Thirst
Restricted fluid will lead to a performance dip, but ‘restricted’ is a relative term and the amount of fluid each of us needs varies according to our individual characteristics and the environmental conditions. Rather than looking for a magic formula, use your inbuilt interactive fluid gauge: thirst. Simply responding to your thirst means you’ll get enough fluid. And that’s probably much less than you think it is.

2 Don’t Overdo It
Don’t make the mistake of thinking that drinking more than you would by just following your thirst will magically make you go faster. It won’t. Our normal physiological response to exercise and sweating is to lose some of our body weight in fluid. Typically, when we drink to thirst we lose about two to five per cent of our weight because we don’t replace 100 per cent of our sweat. But that’s normal, and doesn’t represent dehydration. Drinking to thirst prevents dehydration. Drinking enough fluid to prevent weight loss won’t make you go faster. In fact it leaves you overhydrated.

3 Go With The Flow
If you’re not able to meet your thirst, you’ll probably run around three to four per cent slower. That’s a lot if you’re aiming for a PB, but not quite the numbers thrown around by product manufacturers. Still, if there aren’t enough water stations or you’re unable to take in enough on the run, your performance will suffer. As most marathons have plenty of water stations, the first scenario probably won’t be a problem, but do check ahead and carry water if stations look thin on the ground. However well-watered the course though, it’s crucial that you learn to tune in to your thirst, and to drink comfortably on the move at race pace. Once you’ve mastered this, relax. Trust your physiological thirst mechanism and you might be surprised how it changes your running if you can unchain yourself from the hydration issue.

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