Over time this will be easier. Be sure to maintain a classical sitting right in all exercises. Have the person who leads his horse rope guide him in a slow Gallop and try to keep one half sitting using the thigh muscles inside. Once their legs are able to lift up on the trot and keep the Middle sitting without the aid of stirrups in three steps, it is time to incorporate some balance in its routine exercises. Practice exercises with arms to the sides and rotate outward, then turn toward the Center. Keep your hands on your head and turn sideways. Another good exercise is to put your legs up so that your heels touch the buttocks, this is sometimes called the frog position and can help open the hips and helps position seat bone, also help loosen the knees to achieve a better relaxation and balance.
An effective exercise affectionately known around the world is to rotate 360 degrees on the horse's back. First pass his leg over the neck of the horse to sit on the side, then turn sitting in front of the horse's tail, turn toward the opposite side, then back toward the front. This should be done with the horse in a position then arrested when more confidence is You can make different rhythms, while the horse is with the rope. Scissors is a little more advanced. In this practice swing his legs forward, backward then upward and rotate in the air to finish against the horsetail.
Repeat the exercise to finish in a forward position. You should do these exercises on a routine basis to maintain tone balance. Not only these exercises will improve your balance, it will be a rider stronger and also more secure.