A rider must always remenber that a horse is narrower in front than behind, therefore, if his shoulder and hip are both on the wall he must be crooked.
Not straight:

What the γυμνάσιο (gymnasium) was for the young Greek, the institution in which he developed the gifts of his body to the fullest and the greatest harmony through daily exercises, that is the riding arena for the horse.
In the arena we do horse gymnastics where we develop the horse’s muscle structure through a system of stages of ever-increasing exercises.
These exercises follow one another in a logical sequence to enable the muscle to easily put the skeleton into the carriage it requires for service under saddle and to move with strength and agility.
Photo: Gustav Steinbrecht (1808 – 1885)
Lateral bending in the body is one of the first exercises and a very important one. Because of the lateral bending, the inside hind leg will step under the point of weight. This is the beginning of shoulder-fore and shoulder-in and it is the basis for all dressage training up to its highest perfection.
© Das Gymnastium des Pferdes – Gustav Steinbrecht – ISBN – 978-86127-357-8
A horse can ‘go lame in the mouth’ when:
- the outside rein is too long with no contact
- the inside rein is too short and stiff
Therefore the stride is shorter on the inside.
To correct, ride shoulder-in. This helps to improve the correct lateral bending and encourages the horse to take a contact with the bit on the outside. And it encourages the inside hind leg to engage well forwards.
Sometimes this fault is easier to correct by interrupting shoulder-in, riding a volte, and then proceeding with a new shoulder-in.


