Had a good run tonight after my days rest yesterday. Idea was a short tempo run, based on a HR of 170bpm. That was the plan at least. A few mins into the run, I was over that limit and going strong so just went for it. I wasn't going flat out, just comfortably hard.
My 4km pace was pretty good (by my standards) doing the distance in 21m 53s (average pace of 5m 28s). Made it home (after a brief walk and a leisurely jog) in 31m 15s (5m 40s average). Average HR was 175bpm.
My next goal for this sort of run will probably be the 5km mark, but there's another obvious milestone...doing the whole 5.52km in less than 30 mins! Now that will be tough, given the idea isn't to go flat out :)