Doubles... I think I'm going to have to start doing them. My keys for 3:15 are 70 mpw and 155 lbs. Adding intensity has made the former harder. Hudson says 70 mpw is about the most you can do in singles. For me, because I'm so much slower than Hudson anticipates, that point is probably less. I've been trying to do 10+ miles w/ a workout on Tu and Fr, a med long run on Wed, an easy 10-miler on Sa, and a long run on Sun. I think the Fr, Sa, Su stretch is probably taking a lot out of me. If I made Saturday, and possibly Wednesday, into doubles, the schedule would probably be a lot easier to handle and let me consistently reach 70 mpw while keeping the workouts. I hesitate on doubling Wednesday though, since I have a deep attachment to the mid-week medium long run. If I'm doing 10-12 on Tu & Fr though, maybe that would suffice. I really don't like doubling because of the time it takes, but I'm less than 8.5 weeks out now, so I'd only be doing it for the next 5 or 6 weeks.
I noticed that Rubio and Hudson differ on which days to double. Rubio would have you double workout days first (Tu and Fr). Hudson has AM moderate/PM easy on Wed and AM easy/PM easy on Saturday. I lean toward Hudson only because I always feel like I'm going to pull something when I shuffle around the evening after a hard run. At 37, maybe I ought to look at that masters chapter.
I was a good boy and did about 10 minutes of stretching/core today after an easy 9.3 miles @ 9:11/133bpm.