Exactly four weeks ago I mentioned I had hit an aerobic plateau, with the plan to change up the workout routine and try again afterwards. So today I tried the same intervals workout on the treadmill that I wasn't able to complete two other times, and the result was ... still couldn't finish it =(. On a positive note, I got farther this time than I have in the past. I think there are a few interesting things here. First, I didn't lose any aerobic fitness during my two-week vacation, and perhaps even gained some, which is great. Next, the bike sprints didn't translate over to running aerobic capacity quite as dramatically as I would have liked. I did three treadmill workouts over those four weeks, and the rest on the bike. Anyway, in retrospect, it seems that I simply bit off more than I could chew. When I went from my previous completable interval workout to this one, I took about 9.16% off the mile pace for the sprints. Apparently that was way too aggressive. I should probably jump in increments of 1% or 2%, rather than 9% all at once.
Edit: This week (a week after I wrote this post), I went halfway (yes, enginerds, I'm binary searching for my maximum). My previous completed workout was at X mph sprints, and I was failing at X+1 mph, so I went at X+0.5mph today. I made it through and got a stitch right after my eighth sprint, which I cranked up to X+1 mph. It feels good to complete a workout. Next time is X+0.7 or X+0.8.