The circle of aids coincides with what is known as the horse’s ring of muscles. The principle was first described in the early 20th century by Dr. Georg Simon (1871–1941) and Dr. Wilhelm Haase, two influential German veterinarians and riding theorists. Their combined research into equine anatomy and classical training revealed that a horse’s natural balance — the harmony between bending and stretching — depends on the uninterrupted flow of energy through the interconnected muscle ring.
They found that the horse’s muscles work in a continuous circular pattern — beginning at the poll, running over the neck and topline, across the hindquarters, along the belly, and returning through the chest to the jaw. When this muscular circuit remains supple and connected, energy travels freely through the body, allowing balance, elasticity, and strength to develop.
In the same way, the rider’s aids must act in a closed, harmonious circle. As the horse’s muscles function in an unbroken chain, so too must the rider’s legs, seat, and hands coordinate to guide and recycle that energy. Thus, the circle of aids mirrors the horse’s ring of muscles — uniting anatomy, biomechanics, and refined riding into one complete system of communication between horse and rider.