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Drink to Thirst or By Plan? The Big Guns Weigh In




How do we reconcile the thoughts of two respected, and usually correct triathlon information sources in this important matter?

Last weeks blog, Drink to Thirst?  Hah!  It Doesn't Hold Water,  was not only fun to write but one able to bring out a more complete picture of hydration.  In short, what works for one athlete, or one subset of athletes, doesn't necessarily work for all.  In this case, it definitely doesn't work for all.

Triathlete Magazine, recently quoted a study of cyclists where some drank to thirst and others followed a regimented drinking plan. "What they found? Prescribed drinking mitigated the impact of dehydration better than drinking to thirst."  They took that a step further and had the athletes rehydrate "to match their sweat loses, what we call individualized hydration protocol, they performed better, they cycled faster and they had lower body temperatures.” This suggests that prescribed drinking to match fluid loss in the heat provides a performance advantage."

We need to keep in mind that the studied athletes were elite level and other factors or variables may be involved as well.

It's been suggested that drinking to thirst is a recommendation that works for the slower athlete.  If you are going a bit faster it may be better to at least consider a plan.  It is good to use early parts of a race when the GI tract is working fine to absorb both carbohydrate and fluid.  Later in the race, even though you may be thirsty, the gut may not absorb as much. Don't drink excessively and use common sense.

Joe Friel, of the Triathlete's Training Bible, in personal communication noted, "Drinking to a schedule is not supported by the research. And the downside is that people come up with a schedule that is unrealistic and then drink themselves into hyponatremia. There have been several such deaths in marathons by back of packers. Even among those who should know better, i.e., a physician who died over drinking G-ade at Boston a few years ago. It’s dangerous to suggest this to people."

I believe both of these rehydration philosophies right and here's why.




A couple years ago, at the Ironman Sports Med course they have at the Royal Kona Resort in Kona the week before the World Championship, having previously been on the faculty, I was encouraged to attend a cogent lecture on Death in Triathlon.  The hydration issue was presented more like a spectrum rather than a yes or no situation.  

The speaker went through those hyponatremic deaths addressed by Joe Friel and common factors seemed be slower runner, cool day, women slightly more at risk than men, fluid overload thru overhydration - drinking excessively.  A little later, the speaker challenged the audience with a question like this.  OK, you’re supposed to, in one sentence, write the hydration plan for Pete Jacobs and Frederik Van Lierde, both winners in Kona, a 12 hr IM finisher and a 17 hour lottery finisher.  (Oh, on an 80 degree day and a 30 degree day.)

 In my mind, since the energy expenditure/ambient conditions are wildly different for this foursome, so would be their race plans.   Maybe Kona athletes are a subset unto themselves.  Potentially more knowledgeable, better experienced with trial and error of what works for them as individuals, that kind of thing.



Pretty ride for Women for tri (on top tube)

The actual percentages of our Kona hydration survey were as we obtained them in the blog, 86% either using a plan or “both.”  (Their words.)  I plan to repeat this study in October by the way.


So, we can see both sides of our street here.  I suppose that leaning more toward the athlete you’d find on the Kona pier at 6:00 am race day planning a 10 hour or less race, having at least the skeleton of an idea of both nutritional and fluid needs wouldn't be surprising.  However, the "everyday competitor" maybe a little newer to the sport or somewhat slower, hydration guidance would be to let thirst rule the day.


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