My coach has me doing weekly strength running, something I've never done before. Wowzers.
10 min warmup z2
5 x [5 min upper z4 (10:00 pace) then 5 min lower z4 (10:40 pace).
Considering last Friday was the first time I've ever run 5 miles straight, and that was in z2, I thought this was a bit wackadoodle. So, as a compromise, I pushed on the upper z4 runs (even hit 9:30 a few times), then ran the lower z4 for 2.5 mins, walked for 1.5 min (drinking water), and ran the last 1 min of the interval. Then started it all over again. I did run all of the final lower z4 interval. I probably could have run more, but give then this was 50 minutes of continuous HARD running, I didn't want to push it. Still managed to get in 5.63 miles.
Now my challenge is not falling asleep under my desk. I'm wiped.