5/1 repeats, 2 hours

I just got back from one of the most difficult workouts I've done in years. Bill and I discussed a plan where the long weekend runs would be a combo platter of running and walking. Distance isn't necessarily the primary goal (big change for me!), it's more gauging how I'm feeling and how much energy I'm exerting. For example, there's a 5K feeling, and a half marathon feeling as you're running.
Today's run called for a 5K or 10K mindset for 5 minutes, then walking for 2 minutes. I did this for two hours in the St. Anthony Main/Stone Arch Bridge area in Minneapolis. I have only run in this area once or twice, so it was nice to get to know the streets and paths.
I'll list my splits here for the 5 minute runs and describe in more detail afterward:
Split Avg mile pace Distance covered
1 7:44 .65 miles
2 7:20 .69
3 7:23 .68
4 7:43 .65
5 7:31 .67
6 7:49 .64
7 7:55 .63
8 8:44 .58
9 8:09 .62
10 8:06 .62
11 7:58 .63
12 7:52 .64
13 8:02 .62
14 7:55 .63
15 8:09 .62
16 7:59 .63
17 8:10 .61
Total distance including walking: 12.3 miles in 1:57:43

During the walking portions of one of the repeats in the middle, I stopped at my car for water and a gel. I kept with the 2 minute time for this break.
I went up and down and across the Mississippi River, so my routes were pretty varied. There were some big hills in there, and some very icy patches. I think for split #8 above, there was a stretch through a park that was solid ice/snow for about 200 yards which slowed me down considerably.
It took me a little while to get used to the distance and all the stopping and starting. Once I got into a bit of a groove, it looked like I locked into a 7:50 / 8:10 pace. It became a big struggle in the last 4-5 reps, I'm not going to lie.
For the first few, I'd hit five minutes and felt some relief, but it wasn't like I NEEDED to slow down. But by the last 2-3, I needed to rest my hands on my knees and stop for a few seconds. I could feel the beginnings of a flare-up in my lower back for the last half hour or so.
I also felt some flare-up on the bottoms of my feet. I've felt this before in running. But usually after distance training for a few weeks this goes away. I saw a pretty salty face in the mirror when I got back into my car! It felt great to sit down. I can tell my legs will be stiff later today.
For recovery, I made a chocolate smoothie with strawberries, blueberries, and vanilla yogurt. Plus I've been trying to drink more water throughout the day. I downed two bottles already.
So two hours in the books today, with a 3 hour run similar to this later in the month. I might have to drop into the 8:30's to make it an additional hour. We'll see.
Now off to the shower and most definitely a nap!