One more note on the 21-mile long run yesterday. Since I had some troubles with some of the longer runs lately (see failed 14-miler and 18-miler with marathon paced portion), I decided to take particular care of hydration. I took 5 bottles of Gatorade with me, 4 of them are 8 oz (but I overfill them to 9), and the last one is a bit larger, probably about 10 oz. I knew I would have access to a water fountain at mile 7.5 and then again at 14.5.

I had to drink the 10 oz bottle first, because it refused to stay in my belt. For the same reason, I didn't want to refill that one. I haven't finished a single 8 oz bottle by the time I ran by fountain for the first time, but by the second time, I had two empty 8 oz bottles, and I refilled both with water. By the time I got home, I was completely out of fluid. I followed no hydration plan; I just drank to thirst, and I allowed my cravings to dictate when to take water and when to take Gatorade. I downed the last sip of fluid 2.5 miles from home.

The summary is that I drank ~46 oz = 1.36 L of Gatorade, and 18 oz = 0.53 L of water. And it wasn't even that hot. That suggests that I may need a liter of fluid per 10 miles on some of my long runs. That is quite a bit more than I brought with me on my failed runs. I tried to complete my 14-miler on 0.8 L water, and I think for the 18-miler I had 1.36 L of water. Either the amount, or the sugar or salt, or multiple factors of these was insufficient.

It's a bit embarrassing that I still need to learn the need for proper hydration after over 6 years as a runner, but it is just so counterintuitive that I can run 13-14 miles on no fluid in the winter, and I need a water tower for the same distance in the summer.