I let heat psych me out yesterday, and then by later in the day I really had been affected by heat enough that it was no longer feasible - but I was determined to get the workout done properly this morning. Didn't get out early, and it was pretty darn hot, but I did the best I could - in these conditions, it's less like "fast" and more like "trying to keep cadence and knees higher than they are during the default shuffle."
12 x :40 faster, 1:20 easy
4:00 jog regroup for purpose of convenient counting
5 x 2:00 faster, 3:00 easy