Yesterday I did another set of intervals: 5x1000 meters in 5K pace, with 400 meters recovery. It was quite brutal, especially the last 1000 meters. I almost puked at the end. Here are the splits for the 1000s:

3:59, 4:00, 3:57, 4:01, 3:57

Now I just have to cut out the recoveries and I have a 19:54 5K. :)

I modified my goal a bit. One reason is that I AM getting close to the 20 minute 5K; the other is that lately I trust McMillan's calculator more than RunersWorld's. If you follow the method I mentioned below, type a 3:15 marathon into McMillan's, and you get 20:00, 41:33, 1:32:28 respectively for 5K, 10K and half-marathon. Therefore my modified goals are:

5K: 20:00
10K: 41:00
Half marathon: 1:32

According to McMillan, the 10K is the hardest, because that involved the largest rounding, so I might work on decreasing my 5K time before I move on to 10K. Also, training for 5K is somewhat less time - something I wouldn't mind now. On the other hand, 5Ks are the most painful of these races: if you take them seriously, you SHOULD feel pukish at the end. We'll see. After I get my first sub-20 5K, I'll see what I'll try. It would also be nice to complete a whole 12 week 5K training cycle a la Pfitzinger.