On Monday, I did a podcast with IM Talk for their column "Workout of the Month." In this column, an athlete submits a workout for a coach/athlete from Endurance Corner to complete and then the coach/athlete comes on the show to comment on the session.
This month the criteria they used was: A 90 minute strength run session done during a run focus period.
Rich Swan, from Wellington, NZ, wrote in and suggested a workout consisting of hill repeats. In his session, he used a hill a little over 1200 meters long that he runs 5 times, taking ~5:20 to complete. Completing the hill in this time period yields a HR of 170 and a pretty solid/hard effort on his part.
You can hear my thoughts on the session here: