Also, a pointer for all of you for the next two weeks:
Keep out of your own way by not overstriding. To walk faster, you must strive to maximize stride rate (not length). You have to sacrifice stride length a bit at first to achieve a high turnover rate. So don't step out too far (this will also cause shin splints), but keep your heel plant closer to your body and concentrate on rolling completely from heel to toe and pushing off of that rear foot.