Thanks for the explanation Steve. I understand now, and I think my body is actually glad the reps have reduced a little!!!
Today's run was a good one, 2k reps are not my favorite, but I can appreciate how useful they are for marathon training. It's very cold out there today and it took me a little while to warm up, the wind was bitter and always seemed to be blowing in to my face!
Total run was 10 miles in 67.19 (I think it was actually nearer 9.5 miles, see explanation below!). the 2k reps came out at 7.36 (I think this one was slightly long), 7.10, 7.07 and 7.08.
I think my GPS was playing up a bit today, the first rep felt long and I think it was by about 10 or 15 seconds, so it was still slower than the other 3. Then for the last two it was measuring short so I was running over distance by about 0.30M.
Another hard session done and on to my hills session planned for Saturday. Steve, have you any suggestions for structure of the session? distance of rep, effort or pace etc?