Spiral Seat for the Walk The spiral seat gets its name from overlapping muscles with fibers that are aligned in the same general direction. These muscle tracts follow a spiral path around the body. In the images below, discussions about major muscles and skeletal parts are color coded. The walk aids are discussed after the diagrams. The walk is the most difficult gait to ride correctly because riders are used to the human "walk," which is really a stepping trot (diagonal coordination of arms and legs with no suspension). This interferes with the timing of the 4 beat walk, which is more like crawling on hands and knees (alligator style walking, except that we and horses have fancier shoulder and pelvic structures than reptiles). Another source of interference with the walk is tension anywhere in the body. Reasons for relaxation and suggestions for achieving it are HERE). Exercises to help mounted and unmounted riders with walk coordination are linked at the bottom of this page.
				The iliopsoas muscle system deep along the rider's spine stabilizes and controls following actions of the seat.
					The actions of the iliopsoas are stabilized by the oblique abdominals.
				The rider's spine curves gently to allow the pelvis to float above the horse's lats.
					Relaxed thighs and lower legs help the rider to follow the belly swing.
				The rider's rib cage is optimized for elastic response by closing the muscles at the back (levator costae). Shoulder blades (dotted lines) "float" across the back, allowing hand to be independent of the seat.
					The left latissimus dorsi is contracted, lifting the rider's left seat bone.
				The right lat is relaxed, allowing the brachiocephalicus and other muscles to move the right leg forward.
ABOVE: This is the moment in collected walk just at the end of the pull forward on the grounded right diagonal pair (right and left designations based on the grounded or stance hind leg). In the next instant, the left fore will be in swing phase and the horse will have maximum bend in the rib cage to the right and be standing on the two right legs while the swing phase left legs make a "vee" under the left leg of the rider. Sequential frames of the walk are HERE (see Frame Three). Bob Tarr photo. My shoulders are level so my hands are able to follow the head bob (very subtle motion for the collected walk), my spine slightly curved to allow my lower body to move with the horse. My feet are not level because my left leg has stretched down and right in following the belly swing. This is why muscles around the hip joint and thigh should be relaxed. My pelvis is up on the left, lifted by the contracted latissimus dorsi plus position of the swinging back. Dressage fanatics will note I missed the line from M to H by about a meter, but I got my horse straight in preparation for half pirouettes in walk. Anchorman has nearly finished his head bob down associated with the placement of his right foreleg, so you can see his braids past the poll. His skull is translated left (a horizontal position involving the skull and first neck vertebra). He is biomechanically straight: his knees and hocks are exactly lined up. His shoulders are centered ahead of his pelvis so that the belly swing to the right (shifts the center of mass over the grounded right legs during the "vee") is due to a shift in the rib cage. In the diagram BELOW, which shows Anchorman's back at the moment of the photos above, you can see the gradual curve or "bend" in the ribcage (thoracic spine). A rider can feel muscles working to swing the belly from side to side. The temptation is to rock the pelvis in order to follow the belly swing, but if the iliopsoas muscles LIFT each seat bone alternately and shift it slightly INWARD, the rider will not sway away from the midline of motion (note my shoulders stay centered) and the horse will not wander off a straight course. By the way, the horse also has an iliopsoas system to help it with pelvic movement. Click on the image to view it at full size.
Axial Skeleton
Pelvis and shoulder blades
Bony portion of ribs
Cartilage portion of ribs
Outline of horse with belly swing	Outline of straight horse
In the diagram BELOW, you can see the "X" formed by the two lats (front legs) and the gluts (fascia connecting the muscles not shown) as they are in the image above. A rider can feel the muscles working in the order in which the legs are cycled in the walk. Click on the image to view it at full size.
Latissimus dorsi and medial gluteal connecting the Left Fore and Right Hind diagonal pair.
Latissimus dorsi and medial gluteal connecting the Right Fore and Left Hind diagonal pair.
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