Thinking about it later, I tried to find what the reason could be, since I should be even better than Friday simply because of Friday's work out. The time was almost exactly the same, the distance from last meal was about the same. I was not hungry yet, not at all. My diet had been the same.The weather was same, sunny and warm. The only difference I could think of was that Friday's run was after several nights of biphasic sleep, and today's run was off the back of two consecutive nights of monophasic sleep. It's not a true scientific test, but that's the only difference I could think of.
Also felt more tired after the run. In the afternoon I felt very sleepy. So much so that I took my evening nap in the afternoon. From 1545 to 1610. Just 5 minutes to fall asleep since I was almost falling asleep already.
The nap was good. I did wake up with a headache but it went away after a while. And still had the energy to stay up till midnight.
Actually past midnight. Slept at 0030 with alarm for 0510.
Woke up 0510. Took some effort but woke up.
Energy levels: 98%
Body: Fine, no tiredness from yesterday's run