The couch potato to 5K running program is great! It's a slow, gradual build and everything makes sense, until week 5, day 3.
Week 5 day 1: run 5 minutes, walk 3, repeat.
Week 5 day 2: run 8 minutes, walk 5, run 8.
Week 5 day 3: run 20 minutes.
Where in the world does that come from??? It seems like the next logical step would be run 10 minutes or 12, but going from 8 to 20 is such a huge jump. I didn't understand it the first time I did the program and I don't understand it now.
Week 6 is back to more moderation and more rational distance building.
day 1: Run 5, walk 3, run 8, walk 3, run 5
day 2: run 10, walk 3, run 10
The 20 minutes seems to come completely out of the blue and it's the absolute hardest day of the entire program. Sure, I finished, but it was hard and at one point I was running below 6 mph. It didn't help that I couldn't go to the Y or run outside, but I had to use a treadmill in front of a mirror. If there's one thing I definitely do not want to watch while I run, it's myself sweating and struggling with breathing. I tend to get distracted by my feet and my arms and gravity, and my form generally suffers, rather than improves with visually monitoring how I look. The difference is that I see it, rather than feel it. Just excuses though.
The bottom line: the 20 minutes seemingly comes out of nowhere, felt terrible, but was finished. I rule!!! :D