Today is speed day!
I did one-minute alternate runs by 25 sets to run a total 50 minutes.
In alternate runs you jog for a minute, and then run fast for a minute,
and repeat this cycle 24 more times.
I learned this training from "Running with the Kenyans" by Adharanand Finn
who did the same training with Kenyan runners in Iten.
It's a great way to improve your ability to surge as well as to quickly recover from a temporary exhaustion.
Each quick run is short, and soon to be rewarded by a short job, but because there are so many sets, when the first set is over, you can never imagine you will be able to go through another 24 sets. But as you knock down one set after another, the prospect of completing all 25 sets overwhelms the initial fear of failure. And when you finally complete the entire sets, you feel ecstatic!
It is a good break from tedious long runs at the same pace. I will do it again probably after I have done a couple of 20 K runs.