I have been focusing on getting my speed back lately. It has been working.

Yesterday morning, I had an awesome run of 15.4 miles which took me 2hours and 3 minutes.

This morning, I mixed it up and here is what went down:
350 stair repeats 60 minutes
10kms as fast as I could - 48 minutes (my best 10k time is 41.xx on fresh legs)
70 sprints on the stairs.
All in all, this workout took me 2 hours - not bad at all!

I do however have a dull ache on the back of my left knee - I have been faintly limping for the past two days. It goes away after 20 or so minutes of warming up but comes back after an hour or so. I will mix it up by swimming tomorrow am and see if it helps.