(Note: Today’s post is from guest blogger Allison Tai, owner of Urban Fitness Movement.)

Allison Tai says 'you know best.'

I ran a stair race this morning that took me six and a half minutes. That’s right, six and a half minutes. Even the group at the back took around 15 minutes, which leads me to believe that race times were about equivalent to that person’s mile time plus about 5%. I have never seen a water station in a mile race, yet there were two water stations on this course.

As a coach and athlete, I realize that water consumption during exercise can be a deeply personal issue for people. Some cling to water bottles during 30-minute yoga classes, others forgo hydration during two-hour hard interval sessions. But do either of these groups of people need or not need water? In Dr. Seuss fashion, I believe the answer is yes.

As has been shown recently, a 1-2% dehydration level (the amount typically agreed to trigger thirst) is not likely to cause a serious loss in performance. Ask Haile Gebreselaise if he was dehydrated when he ran the world record for the marathon, and he would tell you that he suffered a 10% loss in body weight due to dehydration. In fact, the faster you run, the more likely you are to be dehydrated at the finish line*.

Allison Tai listens to her body.

So what about the piles of studies that show dehydration to be a big factor in a decline of performance? The same studies funded by bottled water and sport drink companies? Well, most often, the participants are in a forced state of dehydration and they are not allowed to drink according to their thirst cues. Of course, performance declines. Yet somehow, this decline is attributed to dehydration (and thus thirst being a poor indicator) as opposed to correctly reasoning that people should drink when they are thirsty lest their performance suffer. Suddenly a major part of sport performance is who can drink the most water. And people started dying.

Enter hyponatremia. Originally (and often still) thought to be at the opposite end of the spectrum from dehydration, it caused a major backlash against “overhydrating” some years ago. Interestingly, the sport drink companies managed to make lemonade from these lemons so to speak — by stating that electrolytes would prevent you from swinging either way. As we have seen from the fact that 30% of all Ironman triathlon finishers have been both dehydrated and hyponatremic, the spectrum appears to … well … not be a spectrum after all**.

So, if I have convinced you to forgo water and become as dehydrated as possible in order to run faster, you have really missed my point. The main problem with studies that look at dehydration is that they are typically performed in a lab under unnatural conditions with a total disregard for thirst cues. My argument is that yet again, you know best. If you get thirsty when you run and you have no water, that likely impacts your performance (not to mention your enjoyment) but if you do not get thirsty, it is doubtful that swigging water will give you game (maybe just a sloshy tummy).

*http://bjsm.bmj.com/content/early/2010/11/15/bjsm.2010.074641.short?q=w_bjsm_ahead_tab

**http://www.rice.edu/~jenky/sports/salt.html

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Allison Tai is the owner of Urban Fitness Movement. Email her at info@urbanfitnessmovement.com or call her at 778-989-1836.