Biomechanics of the dressage or spiral seat

Riders are able to affect critical performance muscles of the horse if seated correctly behind the withers. The saddle should be placed so it does not interfere with the shoulder blades and the girth should not clamp or irritate pectoral muscles. An interfering saddle will inhibit movement of the front legs. Girthing too tightly may result in a "cinchy" horse. Irritating the "pecs" may cause pinned ears with tossing head, the usual indications of cinchiness. The rider may be bitten if the horse is seriously annoyed by hasty, rough handling of the girth.

The signature of an irritated caudal deep pectoral (medium blue muscle at the rider's ankle) is a groove visible from the side. Horses with well developed pectoral muscles will have a groove which runs from chest back toward the belly. A gentle stroking of these muscles should reveal no lumps or stringy areas (spasms or even damage to the muscle sheaths). Good muscle feels like very tough gelatin and is springy.

LEFT: This diagram shows how the rider's seat and legs give aids to particular muscle groups to guide the horse for basic gaits and transitions.

The leg on the concave or inner side of the bend is usually placed about four inches ahead of the outside leg.

The rider's pelvis is resting on the "lats" (latissimus dorsi) with the lower leg in contact with the thoracic part of the serratus. The muscle above the serratus with fibers running the same direction is the splenius. The heel is able to touch the caudal deep pectoral area behind the elbow. Reins are held so they support the muscle fiber direction of the serratus.

Why the ROLLKUER?" There is an increasingly common practice of "riding the horse deep." This has two general forms. One is the "rollkuer" shown at left. The other is the practice of "showing the horse to the ground" which is a stretching exercise. For either rollkuer or other stretching exercises, a heavy contact encourages a horse to contract its cervical trapezius and thus to hold down its withers (undesirable).

Experts are going to ride their horses as they see fit, but amateurs and beginners should understand that the rollkuer puts the breathing apparatus of the horse at risk. Further, when the structures of the tongue, jaw, and hyoid apparatus are stressed, the response of the horse is often to exhibit faults with the tongue. Placing a crank noseband addresses an external appearance of an internal issue. While stretching exercises do not invariably press on the airway, if done improperly, the horse is dropped off a sustaining contact or encouraged to bore (hang) on the bit.

Colored text blocks refer to colors of structures in the diagrams.

ABOVE: Seen in top view, **diagonal pairs** of legs and some important controlling muscles (the horse is in the same phase of the trot as the side view above it). Black circles indicate the rider's seat.
Black circles show the placement of a rider's buttocks, which can feel the pattern of contraction (pink) and relaxation (pale pink) of these muscles for each gait. The seat is principally over the lats, but the fascial sheet connecting them to the gluts allows their contraction and relaxation to be felt.

When a leg is on the ground, the muscles which control its backward movement begin to contract, pulling the horse forward. Here you see the muscles in the moment of suspension, where the support legs have just finished working and the swing diagonal pair (light pink) is about to land.
The serratus, located between the rib cage and the shoulder blade, has a series of segments which has a wave of contraction which moves clockwise, or in the opposite direction from the front leg. This is an example of TORQUE. Animation of this muscle in canter is HERE.	Connections to tongue and jaw from the rider's lower leg are shown in medium blue. These muscles overlap with the caudal deep pectorals at the rider's ankle. Note the critical placement of the HYOID apparatus. The serratus muscle is also shown HERE.	The contracted left lat connected to the arm bone has finished pulling the arm back, aided by the deep caudal pectoral and the thoracic serratus (latissiums dorsi). Color indicates contracted muscle.	Relaxed medial gluteal muscle (fascial sheet linking lats and gluts not shown). See below for the way the muscles operate seen from the top. Color indicates relaxed muscle.
Ligaments	Skull	Rib cage	Legs and pelvis

The **elastic ring** combined with some muscles shown in the top diagram. More discussion of the function of the elastic ring and how the aids affect it is **HERE**.
ABOVE: The hyoid apparatus is a critical part of the horse's body in terms of response of tougue and jaw. It is shaped like a swing or a "jaw within the jaw" and has a prong out the front which is embedded in the base of the tongue. The windpipe passes through it and the thyroid gland rests on the pair of prongs at its rear.	The skull is shown in top view moved slightly left horizontally (called translation). It requires a sophisticated, supple horse to move ONLY this joint. Degree of position of the skull and neck vertebrae is the result of balancing leg, seat and rein aids.	Scalene & longis colli muscles (front) and abdominus rectus (belly)	Ligaments
Legs and pelvis	Rib cage (with cartilage portion shown in lighter yellow)	Connections from rider's lower leg to tongue and jaw via the hyoid	Link to the Spiral Seat and an animation of how the seat works.

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