(Gary's foot...photo by the owner)
Having recently been on a beach vacation, I was in a unique position to observe bare feet. Not to fulfill a foot fetish, but to compare my lifetime runner's feet with those of sedentary people.
Leaving aside the black, misshapen or missing toenails that I come to accept as normal on my feet, what really struck me were my tendons, and that's what set me to looking at the tendons of other people.
Yes, tendons. My 5 tendons, one for each toe, running back from my toes up the front top of my foot, differ significantly from those of non-runners. Mine are quite prominent and stringy looking, even when my toes are not flexed, while most other people's are largely invisible, not standing out at all from the rest of the foot.
I'm no exercise physiologist, but I can only assume that this must be the result of thousands (millions?) of extra footstrikes over the years.
If you're just dying to read more and to see some anatomical drawings, see here and here.