I have a couple different types of anti-fatigue mats in my shop and
they do help extend the amount of time I can stay on my feet. I
recommend them to anyone that do not have them and stand on concrete.
As for shoes, I have tried many different kinds of shoes and cheap
tennis shoes are by far the worst for me. I have a high dollar pair of
safety shoes that are great as long as you are moving(walking) and not
standing constantly. If I stand in them for extended periods, like
doing lathe work and such, my ankles and lower back just kill me and it
even lingers into the next day as well. I plan on going to a foot doc
in the near future just to be sure I don't have a foot problem coming
on. This last year it all has gotten worse. I know age has nothing to
do with it either.........LOL!! Just turn 40 last month, and compared
to some on here that is young by a long shot.

I will have to look into the Birkenstocks, my wife like to wear them.
I just would never thought about them as a shop shoe. Go figure!