How to treat very long toenails (Onychogryphosis)?
If you have very long toe nails and it is not fungal nails (onychomycosis) then it is almost always a condition called onychogryphosis or mechanically induced nail trauma. The stem cells that grow the nail are permanently damaged and you have a very thick and difficult to trim nail- but it is usually a normal color. This is especially common on the first and the fifth toenails.

This link provides information how to care and prevent problems associated with long toenail. 

I hope that particularly older runners will get ideas how to prevent and treat long toenails.