Hand position when riding

The usual guide is that you should be able to draw a straight line from the rider's elbow to the horse's mouth. That said, it also depends a little on the horse's conformation and shape. If the horse goes well behind the vertical, for example, the rider would often have to lower the hand to keep that straight line, and that may not always help if the horse is already behind the vertical.

When we talk about the rider's hand position, the most important thing is usually body control, so that the hand can act independently of the body. Thinking too hard about holding the hand in a set position tends to make you tense in the shoulder and lock your arms to your body. Work instead on using the hand independently of whatever the body is doing, and on following the horse's movement.