10k r26 80% HRR - Kentucky fried legs

Well the schedule called for a 10k r24/26 80% HRR today - so as I managed to get into work early enough to do it with a little warm up I set myself up for it - I did have in mind to start hard and depending on how it felt push on - with the get out clause of the 80% cap should I feel it wasn't there - it wasn't - the legs are fried at the moment - every single drive and recovery sent a small aching/burning through them - even as the pace dropped the pain remained. Have a few niggles with the knees and back - but superficial at the moment - just old age I guess :lol: