"If you cannot live together at the start; Be the one living at the end .... かもしれない" - MT4K
What they say they've done now is that you will sprint by holding down the trigger on the Xbox controller fully, and if you press A at a junction point in the trees, Connor will go up, as opposed to forward.
Assassin's Creed Wiki: Slate Vesper
But as for the sprinting thing, I'm still confused. We've obviously seen Connor running at two different speeds (he jogs away after killing the wolf, then sprints toward Silas) and I don't see how that's possible without using PS3's X button. It's not like the right trigger is pressure sensitive.