What an error of judgment you made when revealing that you are a podiatrist!

As I have worked up to 100 mile rides, at about the 4 hour mark, I begin to develop a soreness/tenderness in my left toe. This basically resolves after about 15 to 30 minutes, but it is so sore I would have to limp to run off the bike (IMFL is coming up for me). I say "bascially" because if I apply pressure on it the next day, I can still feel a little tenderness. I have tried switching shoes, with the same result. I do not get this running. Any thoughts?

Thanks

Monk