This week it was 4 miles, for a total of 12 counting the warm up and cool down from my house. I probably ran it a little faster than my true tempo pace. All four miles were sub-6:00 and three of the four were under 5:55. By the end my heart rate was above 175, which is probably too high. But I have been doing a lot of these runs at slower than my tempo pace and below my threshold heart rate, so it felt good to push it past the limit a bit. I was spurred on by trailing some faster runners on the way out and then pacing a friend on the way back who is usually far faster than me but is recovering from an injury and working himself back into shape. I was not, in the end, feeling like I would puke, which is what one of my running partners warns is most definitely not the object of a tempo run. I actually felt OK and I felt strong on my cool down, when typically I feel terrible while running slow after a quality workout. So all in all good news. And a good prelude
I will be running the 30K on Sunday and I now hope to do the entire thing at marathon pace, which I am hoping will be 6:28 to 6:30. If I do that and it feels decent, I will plan to stick with that for the rest of my training and at CIM.
BTW, here is another source for finding your tempo pace based on recent race performances.