This past Sunday I had scheduled a 14-mile long run, part of my ramping up to a 20-mile long run before the L.A. Marathon in March. I might have gone out a teensy bit too fast the first several miles, but that didn't explain what happened around the halfway point.
I made it halfway and took an unplanned break. This run included both Gatorade (every two miles) and gels (every six miles). I haven't used gels on the run in several months so wanted to get my stomach used to them again. During the break I felt a bit tired but figured it was because of going out too fast. After walking for a few minutes I started heading back. I noticed my pace was slower than it had been but, hey, it's a 14-mile run, right? It didn't take long, though, to realize something was not right. By mile eight I started taking short walking breaks. By mile 11.5, I was walking. I thought I would start running again by mile 12, and I did, but I could tell it wasn't happening, saw my pace on the Garmin, and figured why even run if I felt bad going that slow.
What do I mean by "bad"? I don't mean bonking. I don't mean nauseous. I don't even mean tired. I mean heavy legs, sore feet, and just not feeling like running anymore. I just felt bad. On the bright side, walking the last 2.5 miles meant that I walked the fatigue and soreness out of my legs. I actually didn't feel tired when I finally made it home.
So, I could just plop down and chalk it up to not being my day or I could figure out what went wrong. The previous weekend I ran nine miles like it was nothing. I did the whole thing forefoot striking, too. What could have happened in the past week to make the wheels come off like that? Maybe having nachos as my sole meal the day before was a bad idea? Maybe only doing one morning run (a nice 4-miler on Friday) last week messed up my fitness? Maybe that Friday run was too close to Sunday's run? Maybe using gels for the first time in a while screwed up my body? However, a trip to the bathroom provided me the clue I needed to figure it all out: dehydration. Not during the run but before it. The day before I returned home from a trip to visit family. In an effort to keep from stopping the car every hour for bathroom breaks, I didn't drink as much as I usually do and when we arrived home, I didn't drink water to make up for it. Consequently, I started my run a little dehydrated. Add to that the day was warmer than usual for late November and my usual fluid intake during a run was not enough to make up for it. Dehydration.
So the point of this whole story is that when you have a really bad training session, don't just chalk it up to having a bad day or "one of those things". Try and figure it out to see if you made some mistake so you don't make it again in the future.