Just done the GNR, my first ever race at any distance in 1hr44 and a bit. A Really pleased with the time, much better than I imagined, I ran really well up to 11 miles and then very quickly became tired, weak and finished the last 2 miles quite a lot slower than the other 11, struggling to run really. This change seemed to happen quite suddenly and dramatically. I 'm not entirely sure what's physically going on, but would be very grateful for any explanation and any training tips on how to extend the time I can run at pace for - I'm hoping to do the Paris Marathon next and don't imagine I'll manage a good time if I have to shuffle the last 15 miles.
Can any one help me underOver the last 2.5 miles