A recent post on losing toenails got me to thinking about this: The toenail on my second toe on my right foot occasionally gets very sore after a run. My shoes are about 1.5 sizes larger than my normal shoes and I have plenty of room. It does not bother me every run. In fact, the common element that leads to a problem is not the length of the run, but rather the intensity of the run. I have run easy 10 milers with no problem, but it usually gets sore after a race of any length or after intervals or a longer tempo run. This leads me to believe it is a technique problem that is showing up when I get fatigued. Any ideas on what could be causing this?