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Moments from walk, trot and pace illustrated below show the character of a damaged gait (lateral walk or mistimed walk), the racing pace (a non-dressage symmetrical gait) and selected phases of dressage walk and trot. In the undamaged dressage walk and trot, limb masses are relatively symmetrically placed as they act with respect to the approximate center of mass of the trunk. This is also true of the pace, provided its lateral moment of support is not accompanied by too slow a tempo (animal tips over). An advantage of the pace as a racing gait is that its lateral pairing allows overstep without interfering.
The blue dot within the rib cage midline in the images below marks the approximate center of mass for the body and the blue dot-bar-dot indicates the base of support afforded by grounded limbs. Although a dressage judge may comment that a horse is pacing, true pacing (usually a stepping pace without suspension) is rare in dressage tests. Very occasionally, a horse presents a lateral “piaffe.” Unfortunately, lateral walks are not infrequently seen when the test asks for a “collected” walk. An examination of the phasing of the limbs in a lateral walk shows some of its flaws, its awkward appearance and its differences from pacing. Lateral walking presents serious difficulties for dressage.
• First, a lateral walk is unbalanced with a slightly diminished lateral base of support compared to a dressage walk and is not pacing, which is an undamaged gait, although it is outside the dressage school of performance.
• Second, a lateral walk has stance legs timed so they are relatively ineffective at sending the walk forward (lack of propulsive power from behind). The forelimb of the lateral pair is still braking in the example here, made from overlays of author’s still photos from the 1984 Los Angeles Olympics.
• Third, the neck is stiff and the back is hollow.
• Fourth, swing limbs are not phased so that they travel together in a way that keeps their masses symmetrically close to the trunk center of mass. Retarded toe-off timing of the hind limb delays formation of the next triangular base of support.
• Fifth, the lateralness of the walk need not be symmetrical. Some horses show almost a normal “vee” on one side and a retarded vee on the other. This may mean that there is injury (old or new) or that the horse is “rein lame.” In the case of rein lameness caused by a rider's problematic aids, only expert riding* with an independent seat can remedy the fault, according to Udo Berger.
|Comparison of dressage walk limb swap "vee" with the lateral or damaged walk limb swap.||Comparison of symmetrical action around the pacing and dressage trotting center of mass. CAVEAT: The center of mass moves in three dimensions slightly differently in each gait: these images are intended to illustrate the need for dynamic stability in any gait.|
The limb swap from one half of the symmetrical gait to the other, or the "vee," is near the center of mass of the trunk, so that even though this is the maximally unstable moment of the walk, it is quickly followed by one of the two moments of the walk that is stable with three feet (two hind, one fore) on the ground.
*Udo Burger, 1998 (English edition). The Way to Perfect Horsemanship. Trafalgar Square Publishing (Nicole Bartle, translator).