"Increases your walking speed. Running speed stays the same."
— Inventory description
This item functions exactly the same way as the Walking Shoes do in the main game.
Like all the other unlockables, Fast Walk will be put in the Item Box on subsequent playthroughs and refreshes in the Item Box should it be discarded from the player's inventory at any given time. Fast Walk has to be in Chris's inventory for it to function.
Fast Walk increases Chris's walking speed but has no effect on his running speed. This makes him able to create distance quickly. Chris can also move quickly while in a crouched state with this skill.