Ah, hydration and ultramarathons. It used to be an issue that caused exactly zero problems. When I lived in the Midwest, I never unintentionally became dehydrated in a run. Ever.
I would occasionally do a “dehydration run” where I would purposely consume too little water so I could learn what the physical symptoms felt like. These runs were always done on a small loop with easy access to water, so the danger was low. I didn’t have much of a need for them, though, because it was never an issue in races.
My previous hydration strategy depended on temperatures. If temps were below about 65°, I carried one water bottle and refilled at each aid station. If temps were above about 65°, I carried two. If I were sweating excessively, I’d grab a cup or two of water or sports drink at the aid station after filling the bottles. I was drinking a specific amount of water over a given amount of time and would consume a little more based on sweat rate. I largely ignored thirst because it would cause me to under-drink early in a race and over-drink late in a race.
The strategy worked flawlessly. If anything, I had a slight tendency to over-drink. I’d lose some time peeing too often, but it didn’t affect my performance.
Then we started running in arid environments. On shorter runs, there were no issues. I didn’t run far enough to hit a point of dehydration. It did become a major issue on long runs. The first time I experienced this was the second day of the Across the Years 72 hour race. I was drinking a few sips of water every lap (one mile). I wasn’t sweating at all due to the lack of humidity and wasn’t thirsty. I hit a serious low that appeared to be glycogen depletion… until I started cramping up. At that point, I realized it was dehydration and went about correcting the problem.
The same situation hit on a dumb-ass adventure run with Jesse Scott from Boulder, CO to Nederland, CO. The trip was supposed to be an out-and-back, but we had very little water. The same scenario hit- no sweating, no thirst until dehydration symptoms hit. his run was actually a little dangerous as we didn’t have access to water. I survived, though.
The third time occurred this last weekend at the Bighorn 100, also in a hot, arid environment. At about mile 20, I started experiencing the symptoms of an impending glycogen-depletion low despite eating enough. It was confused by the feelings until I started cramping, then immediately identified the problem. Unfortunately it took another 20 miles before I was able to consume enough to rehydrate enough to begin running. The same issue hit the second day. Overall, I spent over two hours sitting in aid stations drinking. I also added at least three or four hours to my finish time by walking when I could have been running had I not been dehydrated. My 32+ hour finish could have easily been in the 26-28 hour range.
The problem: How do I determine how much to drink in hot, dry environments? For me, thirst is not a reliable indicator. In fact, I can’t “feel” the symptoms of dehydration until they start affecting performance. Sweat, which was my primary measure, evaporates immediately in the arid air.
The two possible solutions could be to:
- Drink enough until I have to urinate approximately every 90-120 minutes, then use urine color as a measure of hydration.
- Try to calculate my actual hydration needs in arid environments, which would entail weighing myself before and after a run, then calculating how much water would be required to replace the weight.
The first is pretty easy. The second would require more work. Both should be relatively effective.
Considering three of my five planned major races are run in pretty hot, dry environments, this is one problem I have to solve soon.
Any other tips from those of you that live in the hot, dry climates?