Ha!! A tempo run! Honest to FSM, I actually did a non-aerobic workout this morning!
I ran from home to the Gaien Picture Gallery in pretty much normal aerobic pace, though I did push hard up the hill through Aoyama Cemetary ... that was just to get me in the mood for something a bit serious. I stashed by backpack behind my favourite vending machine and then set off to do four of the 1.325 km loops at lactic threshold pace. I wasn't sure what pace to do, but 4:00/km plus or minus a couple of seconds is about what I regard as my threshold pace. The times for the four laps were, get this, 5:19.7, 5:20.1 , 5:20.2, 5:20.5 -- which basically works out to a very even 4:02/km throughout. The effort and heart rate were a different story. Average heart rate: 149, 159, 162, 163. The first two laps felt reasonably aerobic and manageable, but by the third lap I was breathing hard and it never got any easier. To be honest, I was very happy to see the end of the fourth lap and found it hard to imagine that I should be able to run a 10-k race 10 seconds or so per km faster than that. Yikes! I think I'm too chicken to put it to the test.
I also had a good session on Wednesday night. Mika and friends were attempting to run 12 km on the track at 4:10/km pace. I wasn't going to join them, but there were "roadworks" going on in Yoyogi Park, so I did start out with them. But actually they were setting a cracking pace and I refused to stay with them. I ran my own pace and it turned out to be around 4:15/km for the first couple of km, then a couple at about 4:07, then I settled on 4:13/km for the rest. Average heart rate climbed to about 157, but it wasn't getting out of control, so I guess I was staying pretty much aerobic at this pace. When considered in light of this morning's tempo run, this is all fairly encouraging. The aerobic base is high and will allow me to hold 4:15 for much of the race. I just need a few more threshold workouts now to help me hold onto that pace when lactate starts to accumulate and heart rate creeps up late in the race.