Tough session!

Today was one of the toughest little runs I have done for months! It was full of pain... It started OK, but the legs still felt a bit heavy from the last few sessions and the weekend. I did about 2.5k w/up and then hit it. All intervals were supposed to be done at zone 5 (flat out) pace. The schedule was 4x200, 2x800, 4x200 and 2x400. All with full recoveries between each. The 200s started OK, but then the 800s were upon me. These are a nasty distance at this pace/effort and by about 500m you feel like you are going to explode. My HR got to around 88-89% of max towards the end of each one. They were so hard. The next set of 200s were not completed at quite the same pace as the 1st lot! The avg went from 3:47 pace to 4:05pace! Then just to really do me in, a couple of 400's. I was shattered. This was one of those sessions that you put away in the memory bank for later, when you really need it and have to dig deep...