It’s more about the front legs then the haunches…..!
“The turn-on-the- haunches is a balanced movement performed one step at a time. In a turn- on-the-haunches, the horse is asked to shift his weight and balance to the hindquarters. Looking slightly into the direction of travel, the horse steps around reaching with the inside front leg back and out, while crossing over with the out- side front leg until he has walked a circle with the front legs around the hindquarters, bending into the direction of travel.
You can improve the quality of your turn-on-the-haunches if you think of it as a walk pirouette. Not only does it improve the quality of the maneuver, it makes it more functional for the horse and it helps to avoid some of the mistakes that we often see a rider making on the Court.
In a perfectly executed turn-on-the-haunches the horse will turn around the inside hind leg, but it is acceptable, and indeed desirable from a functionality standpoint, for the inside hind leg to step in place as opposed to pivoting while weighted. The only undesirable movement is for the horse to step backward losing the forward momentum of the turn. This is usually caused by the pivot foot being placed too deep under the horse resulting in loss of balance until he is forced to step out of the turn. Loss of forward momentum in the turn can also be due to the horse weighting the outside foot.
To cue for the turn-on-the- haunches, you first shift your weight through the seat to the hindquarters. You then open your inside hand, creating bend to the direction of travel, asking the horse to look to the inside hand in the turn. The inside leg aid is relaxed at the girth. Momentum through the turn is created by the seat and the rider’s outside rein. The outside rein asks the horse’s outside front leg to step over the inside front leg by making rein contact at the horse’s outside shoulder. The rider’s shoulders should mimic the horse’s shoulders by looking into the turn. In the turn, the rider focuses on driving the horse’s outside hind leg. The stationary leg will carry more weight in the turn-on-the-haunches and is strengthened through this lateral maneuver.
Having your aids in time with the horse’s feet is imperative to the success of schooling the turn-on-the-haunches. The reins are connected directly to the horse’s front feet and can virtually “lift and place” them where they should be through the turn”.