Gluteus muscles

Don't be embarrassed! None of this is trivial. In fact, the first muscle to work when you are propelling yourself forward is the hamstrings, so it is okay to feel something there and it's not so bad for your abs to get tired (they do work to keep the torso stable, especially in a fast walk). you don't want to lock your knees, but it is common to lock the knees when you are first learning this. To prevent locking, it helps to engage the arch muscles in the foot. This is tricky with everything else going on and you may instead want to just take shorter steps till you get the hang of protecting your knees by shortening your foot. To get the glutes to work more reliably, it helps to strengthen them on the side. See the second last exercise in the back of the book. You may even want to get your glutes a little sore - then it's easier to find them in walking! It is a little like going up stairs the right way, but most people go up stairs by pulling themselves up and then this is different. You have a good project picked out for the New Year - good luck! Since you are in the East Bay, consider coming to Palo Alto or S.F. for one of our intensive courses - people come here from abroad and are always happy they did so!