Run to Win25 Marathons, 17 Ultras, 16 States (Full List)
Thanks for such a thorough response! The sensation has been persisting since it started, so I think it's probably not circulation (although I don't know if I want to ice and elevate it now, which is what I'd normally try!). Never happened before, and nothing I remember happened on my (uneventful, flat) run.
It's possible my sneakers are getting towards oversized -- I was fitted at a running store, but I've lost a little weight since, and I have noticed that my normal shoes are getting loose.
I'm also going to keep out of heels during the day for a while -- I wasn't wearing them when this started, but I'll take any good excuse to avoid them!