The old shoes were Lake MTB shoes, not tennis shoes. I've since changed shoes and the saddle as well (both were planned regardless of this issue). I have yet to ride long enough to bring on the numbness.

The other day, I noticed that I sometimes get the same sensation when going for a walk in my Chaco sandals. It doesn't happen all the time though. I never have this happen in regular tennis shoes or my street shoes. I don't experience the numbness at all in my other foot or in my hands ever.

Chris