Those new recommendations appeared on the USATF web site just before the Boston Marathon, and there was an article about them in the NY Times that week. I showed them to one of my coaches from Team in Training on the plane on the way down to Gulf Coast.
His take was that USATF was reacting to the people who get in trouble in long races. The people who are taking 4:30-6 hours to finish have run into a lot more problems than the people who are taking 3-4 hours to finish. More than a few people have been hospitalized (or worse) due to hyponatria during and after marathons, whereas the problems due to dehydration have been much less severe. Programs like Team in Training (and several others) have helped encourage many people into running (and triathlon) who take much longer to finish the races than the more seasoned athletes who have historically made up the “typical” marathon population.
We could get into a whole heated discussion about the effects of TNT and of slow amateur particpants in marathons and traithlons. Regardless, someone who is doing a 5 hour marathon should be following a different training, nutrition, and hydration plan than someone who is going to finish in 3 hours.
USATF’s previous guideline of “drink as much as you can” works pretty well for someone who is doing a 3-4 hour marathon. At that speed, you’re eliminating water fairly quickly, and your total water consumption during the race is not that large, even if you have a cup at every aid station. Plus, someone who can finish a marathon in 3-4 hours probably has enough running experience, even if it’s their first marathon, to know when to stop drinking if their stomach is sloshing around or acting funny. For that person, the new guideline of “drink when you’re thirsty” and the old guideline of “drink as much as you can” are almost equivelant.
In contrast, at a 5 hour pace or beyond, it’s MUCH easier to drink yourself into hyponatria if you follow the guideline “drink as much as you can”. You’re going slow enough that you’re capable of downing more than one cup of water at each aid station, and of finishing the whole cup. You’re more likely to drink at every aid station. In 5 hours it’s feasible to eliminate more salt from your body than it is in 3 hours regardless of how much you drink or how fast you run, which is why half- and full-Ironman triathletes at many different levels take salt pills. Plus, someone going at that pace is much more likely to be a first time participant, and may not have the experience to know how his/her body is going to react under the demands of the distance. With the new guideline of “drink when you’re thirsty”, that person is less likely to have the extra cup of water, and may feel more comfortable skipping an aid station if they don’t feel like they need it. As a result, they may be a little dehydrated at points in the race, but if they get thirsty the guideline says they should drink more.
Furthermore, the consequences of dehydration are typically not life-threatening. How many of us have been at triathlons where a significant fraction of the participants took an IV after the race. I would venture to say that at Gulf Coast, with a 90+ degree temp for the run, everybody finished with some level of dehydration. In contrast, the consequences of hyponatria can be life-threatening, and it’s much harder for on-site medical staff to quickly determine if you have hyponatria or heat stroke after you collapse.
So much better if USATF’s guidelines leave people a little dehydrated than if they lead people to hyponatria. My coach’s take, and I agree, was that USATF’s new guideline is to counteract the hydration advice for faster runners that has also been drilled into the large population of slower participants. It’s to help counter the hydration advice new participants have heard over and over again from many different sources that they should drink as much as they can. The reality is that a 3 hour marathoner is going to be thirsty enough to drink as much as possible through the duration of the race, and even if s/he doesn’t, the worst that’ll happen is they’ll finish dehydrated, and maybe need an IV. The 5 hour marathoner, drinking only when thirsty, is MUCH less likely to drink to the point of hyponatria, and life-threatening consequences, than if s/he was downing two cups of water at every aid station.
Lee