After they change direction, Nicholas asks her to position the horse with his ribs away from her inside leg.  The rider is successful in getting him to stretch as she gives on the rein.  They next lengthen down the long sides making sure that he is straight, which means positioning him right.   Nicholas explains that she needs to push him into her hand as she asks him to lengthen.  They have a great discussion on how to accomplish a lengthened trot that isn't just faster.  He explains how he posts to the trot that he wants, not necessarily the trot the horse gives him, and how he can lengthen by doing this.  He uses his short sides to create the energy needed to lengthen down the long sides.