Second long run (14 miles)

Last Saturday I ran a second time for more than 90 minutes, totalling 14 miles in about 1:43. Almost identical to my May 20th run, which had 2 cooldown miles added at the end.

Here's an amazing graph of the results, amazing because they are so similar:


You can see I ran the first two miles faster, and otherwise the "speed decay" curves were very similar. I did start fast on purpose because I also wanted to time a "best 10k" and finished that at a PR 43:43. I would have perhaps continued fast past the first two miles, but hit a train crossing and so the third mile is a "compromise detour" of an unknown exact distance. But anyway, no big deal since I'd have to slow down at some point.

I stopped after 14 miles because my legs felt generally weakened and achy. The last mile stage had a one block down-hill section and I had to decide how to run it "gently", and didn't have the strength to comfortably absorb the energy at normal speed.

If I "had to" (like in a fixed distance race) I imagine I could have continued running at low energy around the 7 mph speed for perhaps another 6 miles (being optimistic now), but I don't know, and I don't think it would be good for me.

It was interesting the curves were so similar since conditions very different. First was early morning (4am) at like 44F, and second around 6pm and a cloudy 63F. Well to say, second conditions were pretty much perfect, not too cool or warm.

It is discouraging to see the slow down, especially since I imagine I can push myself longer and harder, but I don't know. I ran "strong" the whole way, and I actually imagined my second run as better than the first. I was never beyond my oxygen limit, so basically I slowed from general fatigue in my muscles.

I assume my legs were experiencing reductions in glucose availability, and moving toward more fat burning for fuel. I would guess since the rest of my body felt fine, that my overall glucose level was okay, and if I ran slower, my legs could regenerate energy, while the way I was running was depleting them faster than recovery.

So an obvious solution for my next attempt is to try to START at a 7-7.5mph (8:00+ pace), and see how much better I can do after 90 minutes then. A slower pace can also encourage me to use lower power muscles which are the ones that get fatigued. Well, I mean I imagine larger muscles can work best on more energy, but lose efficiency as energy decreases, while a stride that minimized overall energy can keep all my muscles closer to their recovery periods.

I suspect I've not reached a real "fuel limit", and only a "recovery limit", since it was only my legs that were weakened. So we'll see!

I did a couple runs this week, timing my heart after mile markers under different paces, looking to build a pulse vs speed scatter plot, mostly curious about general slopes. I know already that there's a wide range of pulse rates for a given speed, due to whatever factors, but including how long I've been running definitely (heart faster on a 8:00 mile pace after 10 miles, than after 5 miles)

Anyway, I'll keep plugging!