Like when you haven't ridden fixed for a while and you go out and resist on a bunch of down hill stretches?
Damn that hurts! Especially to go down stairs, sit down in your car, lowering yourself by bending your knees in any way including, um, sitting on the throne……and it sticks around for a few days!
Only fixed riders can know such pain, because there's virtually nothing else that requires that type of demands on your quads.
I'm in pain.