Movements of the Horse's Back:
The Special Case for Dressage
Dressage makes particular requirements of the horse's whole spine because of requirements for:
Long contact times for limbs (deliberate tempo) have special requirements for alignment:
Even "bend" (lateral positioning) from poll to tail in terms of overall posture, while the lateral swings of each gait are added to the primary posture.
Lateral bending is emphasized in dressage competitions, but, as Denoix's functional anatomical analysis of equine spines shows, some degree of simultaneous axial rotation is "built-in" to movements of vertebrae. Faber's colleagues made direct measurements on vertebrae that confirm Denoix's analysis and point to complex swings of the horse's spine, repeated during each stride of a gait (symmetric as in walk & trot or asymmetric as in canter).
"Straightness" (minimal or no right/left "tilting" of whole body or body sections during movement).
Engagement as connection of limb mechanics from poll to tail.
Throughness as substitution of balance and fluent coordination for resistances arising from leaning on "locked" body segments.
This movie below shows alternating (side to side) movement of the horse's back from the front. Max is working on a square volte and performing haunches-in on four tracks (right rein). The haunches-in movie begins opposite the biomechanical convention of beginning a stride sequence with left hind toe-down because the movement here is performed on the right rein where the right hind toe down moment is fully exposed to the camera. The walk spinal motion data set at the bottom of the page uses the left hind toe-down biomechanical convention to begin a stride cycle.
Max is supporting himself in collected walk by placing the hind leg under his inside hip. This makes the stride look short, but in fact sets up the gymnastic difficulty of the collected walk where diagonal pairs reach mid-stance and almost the same moment, which establishes subtly important adjustments in timing (phasing) among legs. Max's tempo is about 50 strides per minute. Collected walk demands complete engagement during long limb contact, while sustaining consistent lateral bend, straightness and throughness. Lack of throughness, especially in the base of the neck/shoulder leads to mistimed foreleg timing, usually seen as a a "lateral" walk. The exercise of haunches-in exaggerates the demands of lateral bending in the body and axial rotation in the hindquarters. As Faber and her coauthors state "For [axial rotations], rotations of the thoracolumbar vertebrae were linked to the pelvic AR, and subsequently, to hind limb placement..." (emphasis is mine)
After the movie plays, step through it with the controller to examine how Max's hips move up and down with each walk stride: this lets you see axial rotation affecting the lumbar spine. The first frame occurs just after the two right legs make a "vee" and the belly swing (lateral bend) is concave to the right and convex to the left. As is usual for back motions, the lateral bend is accompanied by some axial rotation (see data from direct recordings). Max also makes subtle chewing motions that readjust important muscle operations in his bottom line (connections to the sternum/hyoid apparatus/tongue). The movie of haunches-in on four tracks from behind on the left rein is HERE. Max is ridden in a treeless saddle specially built for Morgans.
More movies of classical exercises that affect bend and relative elevation postures are HERE.
|Frame 1: RH Toe-down (Hoof beat 1)||Frame 2: Balance on RH-LF diagonal pair||Frame 3: RF Toe-down (Hoof beat 2)||Frame 4: LH Toe-down (Hoof beat 3)|
|Frame 5: Balance on LH-RF diagonal pair||Frame 6: LF Toe-down (Hoof beat 4)||Frame 7: RH Toe-down (Hoof beat 1 again)||Frame 8: Balance on RH-LF diagonal pair again|
Faber and her colleagues say that the motions begin in the hind end and travel forward. This observation fits other data about the highest proportion of propulsion being generated in the hind legs, although fore legs have an essential propulsive role as well. As in half pass, the propulsive action of legs is modified by the primary positioning required of lateral work (see the stroking trajectories of right and left hind legs in the movie).
During gait, each leg enters the same sequence of roles: braking at toe-down to mid-stance, supporting strut at mind stance and propulsion from mid-stance to toe-off. The velocity of a gait depends on the timing (phasing) to permit overlap of individual roles the four legs contribute to the overall smooth performance in a whole stride cycle. Below are the graphs from unmounted horses walking on a treadmill. Flexion/extension appears chiefly associated with head bobbing (coordinated with the flight of hind limbs). Axial rotation is most prominent in the lumbar and sacral spine. Lateral bending is associated with belly swing right or left (see also the Schusdziarra book)
J-M Denoix Spinal biomechanics and functional anatomy. Veterinary Clinics of N. Am.: Equine Practice Vol. 15 No. 1 April 1999, pp 27-60.
Hilary Clayton 1999 (February) The Mysteries of the Back, Dressage Today, p. 28.
Faber, Schamhardt, van Weeren Johnston, Roepstorff & Barneveld. 2000. Basic three-dimensional kinematics of the vertebral column of horses walking on a treadmill. American Journal of Veterinary Research 61(4): 399-406 (DIRECT measurements on vertebrae of Dutch warmblood horses in walk.)
Faber, Schamhardt, van Weeren Johnston, Roepstorff & Barneveld. 2001. Basic three-dimensional kinematics of the vertebral column of horses trotting on a treadmill. American Journal of Veterinary Research 62(5): 757-764 (DIRECT measurements on vertebrae of Dutch warmblood horses in trot.)
Faber, et al. 2001. Three-dimensional kinematics of the equine spine during canter (on a treadmill). Equine Veterinary Journal Supplement 33: 145-149 (DIRECT measurements on vertebrae of Dutch warmblood horses in canter.)
Peham, C., Frey, A., Licka, T., and Scheidl, M. 2001. Evaluation of the EMG activity of the long back muscle during induced back movements at stance. Equine Veterinary Journal Supplement 33: 165-168.
Schusdziarra, H., and V. Schusdziarra. 1986. Reitergesprache: Der Weg zum Unabhängigen Sitz. Pareys Reiter un Fahrerbibliotek, Berlin.
(Conversations with Riders: The Way to an Independent Seat)
This small paperback volume is still in German, but has a series of questions and answers from riders about their seat mechanics generated from the original book, An Anatomy of Riding. There are illustrations showing an unmounted but saddled horse in the walk with the stirrups swinging side to side as the ribcage/spine moves during gait. They offer this as a route to understanding lateral bend.
Schusdziarra, H., and V. Schusdziarra. 1985. An Anatomy of Riding. Breakthrough Publications, New York.
Translated from German by Sandra Newkirk, this book by father and son physicians focuses primarily on humans as they are challenged by the need to coordinate biped structure and function with equine structure and function. There is a thoroughly described set of seven exercises toward the end of the volume. It is intended for instructors and students. The "spiral seat" advocated by these doctors is explained in detail. It is illustrated with technical drawings and photographs of horses ridden with versions of the equestrian seat.