Updated: Jan 25, 2021
Set up your canter depart in a big open area, with no lead in mind, and the ability to pick a direction after your horse enters which ever lead it chooses. When she picks up a lead, make big shapes in the direction where the inside lead is leading a couple times... Then come down to a trot for a few steps only... change direction, and shape of body, and immediately outside leg back to cue them up into a holding inside leg at girth in the new direction. Do these changes of direction in this way regularly. They very quickly learn the purpose of this exercise is that you are choosing the inside leg to lead the canter, as dictated by the shape of your body (See blog on Shaping Your Horses Body). If they break to a trot, immediately correct this back into a canter. If they change leads on you during this break of gait, its no big deal, just keep cantering and find a way soon to go into the new leading-inside-leg direction.