The biomechanics of the vertebral column, although very complex are of vital importance because they form the basis of all the body's movements." (Leo B. Jeffcott, 1980)
Equestrian education and veterinary approaches regard the horse's vertebral column as secondary to the legs. Principles of riding emphasize flexing the horse spine through greater engagement of the hind legs and/or lowering of the neck. In the line of thought that back soreness is only the compensation for hock pain, equine practitioners are treating back pain injecting the hocks.
 
We explored the notion that the horse's vertebral column was indeed the source of all the body's movements.
 
Greater forward transmission of the horizontal forces is achieved increasing the rigidity of the vertebral column. The fascicles of the main back muscles that bridge three to five vertebrae are set into mirror image direction (Black Arrows). Their simultaneous contraction presses the vertebrae against each other (Clear Arrows). The same muscular work is reproduced at the level of each vertebra.
 The mechanism explains why the back muscles stiffen to increase the speed, and vice versa, increasing the speed stiffens the back muscles.  (CLICK IMAGE TO ENLARGE)

 

At first, the explanation does not translate easily in one's mind since the back muscles are simplistically illustrated as long bungee cords stretched horizontally along the vertebral linkage. 
 

Such  illustration is of the Longissimus dorsi muscles group is  overly simplistic and leads to drastic misconceptions.

In reality the Longissimus dorsi group is made of a large number of relatively small segments (fascicles) and is composed of two divisions.
The dorsal division is illustrated on this diagram with the upper red line.
The ventral division is illustrated with the lower red line. 
 

 

Acting in perfect synchronization, longissimus and spinaleus muscles are creating vertical forces resisting the attraction of gravity. Duplicated along the whole thoracolumbar column, this muscular work is creating longitudinal flexion of the spine.

(Click on image to enlarge)

 

 

 

 

 

When the rider tilts the pelvis shifting the seat bones forward, as emphasized in the driving seat, early contraction of the longissimus muscles occur stimulating extension of the cranial thoracic spine, (white arrow.)  (click image to enlarge)
 

 

 

Conversely, when the rider is arching the lumbar vertebrae excessively, the body weight is acting front to back inducing extension of the horse's caudal thoracic and lumbar spine.

(Click on image to enlarge)
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Jean Luc Cornille

 

 Sense of humor: During his military career, Jean Luc totalized 324 days of house arrest. Almost all because of his unstoppable sense of humor. This did not cure him. He just could not resist. Each time an event presents itself, Jean Luc immediately sees the funny angle. For instance, when the first advertising about the pre-shaped heel down riding boots came out, here is what crossed Jean Luc's mind.

 

 

At first I walked funny with my new Heel Down riding booths.

 

 

 

 

                                                                                       

 

                                                                                     

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 email  Helyn

 

 

 

 

 

 

 

 

 

 

 

And Now Let Him Stretch!