06/13/2022
Very eye opening!
What riders actually need to know about anatomy….
The cervical vertebrae are the most flexible. The poll joint (between the skull and first vertebrae) is responsible for most of the flexion/extension (nod yes) and lateral bend here helps relax the whole spine. Between C1 and C2 is where the horse does most of his twisting action- like when the ears go left and the nose goes right. All the joints between the cervical vertebrae have some lateral bend, but those at the base of the neck are actually more flexible. As riders we are often working to stabilize the lateral movement at the base of the neck, while encouraging bend at the poll joint.
The Thoracic region is connected to the ribcage and therefore quite stable. The saddle must sit on this area and not bear weight on the lumbar area. The Thoracic area does not experience much lateral bend, but what does bend is typically around the 10th to 12th vertebras, and is accompanied by axial rotation. This means that when we say that we are "bending" the ribcage, we are really rotating the ribcage. This is why sitting to the inside of the bend is so effective- like sitting in a rowboat in the water, if you sit to the left of the row boat, the left side dips down and the right side will come up out of the water slightly. If you rowed in this position, the boat will undoubtedly turn left even though you may row evenly. The nice part about the bend and rotation happening around the 10th to 12th thoracic vertebras is that is conveniently about where our thigh sits while riding. The rider has great influence over the horse's balance- whether it is on purpose or not!
The lumber spine has some rotational ability but very little lateral bend ability. Even the flexion/extension is not as prevalent as you may think, even though we can clearly witness it when their horse tucks his pelvis. Where all that flexion/extension comes from in the lumbosacral joint. The dorsal processes of the lumbar area point forwards, and those of the sacral area point backwards, making a V at the Lumbosacral joint. This is where the horse can really flex the back up or down. When a horse sits behind and tucks his pelvis, it's the lumbosacral joint that does the work. This is not to be confused with the very close by Sacroiliac (SI) joint. The SI joint is where the pelvis connects to the spine and has hardly any mobility at all.
The sacrum is comprised of 5 sacral vertebrae and they have no movement considering they are fused together.
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