Nike Frees work the minor muscles in your foot so in turn make it much more sore.
If u want to go work out with them to strengthen ur foot so you can last longer at work then that's ok but i wouldnt recommend doing an 8 hour shift with frees.
Go try Vomeros, Motos, or Air Max 2011s.
And if you have pronation problems, you can try structure triax or lunarglides/eclipse.[/Q
Free is all about mimicking barefoot pressure points, and I've done 8-hour shifts with my 5.0's, absolutely no pain. And walking--no matter what footwear you have on--works foot muscles anyway, so what's the difference