well in my case my heels get very sore if i sprint/do fast speed work like sub 4:30 pace- although i try to as much as i can cuz i know its my weakness so i have to work on it.
Someone else said something earlier in the thread that i think is good- who cares about your 400 time? Thats quite a bit different from leg speed anyway(well related obv as all running is but people should be concerned with their 100 time if they are worried about their leg speed)
Btw Uncle Floyd i still think ur selling urself short a little bit- anyone whos that fast must be fairly speedy but i wont dispute you because as ive said im in pretty much exactly the same boat- also it could be ur just tough as hell. If i run a 400 in 60 sec it feels hard but semi comfortable but if i try to run 58 or 57 i feel like im killing myself. Thats why i try to work on speed work when i can.
I think it was stated to me quite succintly by someone who i managed to stay ahead of in an indoor mile last winter "You are the slowest mother f***er who runs fast that i know" (and btw we are only talking about relatively fast here hehe esp in the mile ugh)