You could be right, and I understand why you’d jump to that conclusion, but I don’t think that’s what happened, and here’s why. The effect didn’t last all season nor give me any boost the next one. When I slowed down my frequency of rides later in the fall, I felt my performance decline. It made climbing noticeably easier right from the start of a ride, before I felt winded or tired or like I was having to push through anything. Before this happened, I had already done a lot to prove to myself what I can and can’t do, I’ve had other times I’ve pushed myself to the limit. I don’t think this really was a single event, I think it was a boost in the middle of a bunch of rides. It was the back-to-back rides in the context of my lets-get-going early season riding, though I don’t remember exactly how often I was going. At the time I expected this ride was going to make me sore for a while and tired for a few days, like what usually happens after an extra long ride. I was really surprised when it didn’t do that.

BTW, it might be important that the sprint to exhaustion up the canyon was relatively short; it was 5 miles averaging medium steep, with spots up to 12% grade. I usually ride it in granny gear, “speed 1” on a 27-speed bike, smallest chain ring, largest on the sprocket. To follow the fixie I had to stay in speed 14 (middle chain ring, middle of the sprocket.)