Pound it out Achievement in All-Pro Football 2K8
Pound it out10
Gain 250 Rushing Yards with a Bronze Running Back in a single game
How to unlock Pound it out
Just keep it on the ground. I used Christian Okoye and got the necessary yard in one 10 minute quarter. If you are worried you might lose yards, take him out after you get the necessary yards, as yardage achievements won't unlock until after the game.