Once the work in hand has been established it can be extended to lunge work, utilising the same principles, consolidating the outside reign contact with more forward impedus. Working to the horses easiest side initially, generally the left, the best side should have become obvious during the flexion in halter work, fix a long side reign between the girth and the bit on the right side. The side reign should be adjusted so that when the horse is standing relaxed there is no contact on his mouth this will encourage the horse to reach long and low when he seeks out the outside rein contact. Take a long rope lead, slide it through the ring of the bit on the left side and attach it back to the girth on the same side. Holding the lead reasonably close to the bit ask the horse to flex to the inside then ask him to step across with the inside hind leg. Basically we are now working the horse in hand but with only the inside reign available to us, the outside fixed side reign becomes our consistent outside reign. Walk the horse forward applying all of the earlier described principles developed in the work in hand section, as long as the flexion can be maintained to the inside and contact on the outside reign, the distance the handler is from the horse can be gradually increased. Eventually the horse should be lunging around the handler at the walk on the end of the long lead. Once this is consolidate the horse can be moved into trot.
for further and more detailed information see, “Horses from courses” retraining the thoroughbred ex racehorse, by Scott Brodie on E book available from Apple I books, kindle, Amazon and other E book suppliers.