Yesterday morning, I overslept by a good bit, and got out late enough that I only had an hour and change for riding. Plus, my legs were quite sore to start with, so I wasn't anxious to get out and push the pedals.
I did get out in time to get my 15-mile loop in, and finished it in a few minutes over an hour. It was a hair over 15 miles, with almost 1000' of elevation, all at 14.2mph. Not bad. Mixed results on the heart rate limit, though: I spent only two minutes over 125bpm, which is excellent, but with a maximum of 140bpm (I was trying to beat a traffic light a mile from home). Still, that's better than I'd remembered it being, and I have no complaints.
This morning, I was feeling a lot better (leg-wise), and set out about on time. I did my shortest figure eight (25.4 miles, 1100' elevation), and in just about exactly the desired amount of time (1:45:35, in the event). That worked out to 14.5mph, which was good.
But after the one-hour mark, I had one hell of a time keeping my heart rate down. I think I was just about perfect up to that point, but from there on, I was regularly finding myself over 125bpm. It ended up as twenty-one minutes over, which is terrible, and a maximum of 138, also terrible (especially the why it hit so high; I was trying to overtake a jogger before they hit a jogger going the other way. Should have waited, as I was about 126-7 before the several seconds of effort to pass. Still, I exceeded 130bpm several times).
I'm not sure what I'm doing wrong. It just seems to spike up much more easily, once I've been riding for a while. My average heart rate was just about exactly what I would like, but the spread is just way too high. Need to figure something out.