Mr. Haanstra explains that before lunging any horse he makes sure that the horse leads well and is thinking forward. The demo horse is frisky, and Lammert allows him to go forward until he relaxes. This is a good video to show how to lunge and understand the purpose and expected responses.
Mr. Haanstra brings us a demonstration on lunging. He begins by describing the carriage of the horse, and how the horse needs to move to carry the rider.