Mabu is used for endurance training as well as strengthening the back and leg muscles, tendon strength, and overall feeling and understanding of "feeling grounded".
The ideal horse stance in most northern Chinese martial arts (such as Mizongquan and Chaquan) will have the feet pointed forward, thighs parallel to the floor, with the buttocks pushed out, and the back "arched up" to keep the upper body from leaning forward.