An introduction to the functional aspects of conformation
By Judy Wardrope
The first in a series of articles which set out different ways to examine a horse’s conformation affects their running style.
Why is one horse a sprinter and another a stayer? Why is one sibling a star and another a disappointment? Why does one horse stay sound and another does not? Over the course of the next few issues, we will delve into the mechanics of the racehorse to discern the answer to these questions and others. We will be learning by example, and we will be using objective terminology as well as repeatable measures. This knowledge can be applied to the selection of racing prospects, to the consideration of distance or surface preferences and, of course, to mating choices.
Introducing a different way of looking at things requires some forethought. Questions need to be addressed in order to provide educational value for the audience. How does one organize the information, and how does one back up the information? In the case of equine functionality in racing, which horses will provide the best corroborative visuals?
After considerable thought, these three horses were selected: Tiznow (Horse #1) twice won the Breeders’ Cup Classic (1¼ miles) ; Lady Eli (Horse #2) won the Juvenile Fillies Turf and was twice second in the Filly and Mare Turf (13/8 miles); while our third example (Horse #3) did not earn enough to pay his way on the track. Let’s see if we can explain the commonalities and the differences so that we can apply that knowledge in the future.
Factors for Athleticism
If we consider the horse’s hindquarters to be the motor, then we should consider the connection between hindquarters and body to be the horse’s transmission. Like in a vehicle, if the motor is strong, but the transmission is weak, the horse will either have to protect the transmission or damage it.
According to Dr. Hilary M. Clayton (BVMS, PhD, MRCVS), the hind limb rotates around the hip joint in the walk and trot and around the lumbosacral joint in the canter and gallop. “The lumbosacral joint is the only part of the vertebral column between the base of the neck and the tail that allows a significant amount of flexion [rounding] and extension [hollowing] of the back. At all the other vertebral joints, the amount of motion is much smaller. Moving the point of rotation from the hip joint to the lumbosacral joint increases the effective length of the hind limbs and, therefore, increases stride length.” From a functional perspective, that explains why a canter or gallop is loftier in the forehand than the walk or the trot.
In order to establish an objective measure, I use the lumbosacral (LS) gap, which is located just in front of the high point of the croup. This is where the articulation of the spine changes just in front of the sacrum, and it is where the majority of the up and down motion along the spine occurs. The closer a line drawn from the top point of one hip to the top point of the other hip comes to bisecting this palpable gap, the stronger the horse’s transmission. In other words, the stronger the horse’s coupling.
We can see that the first two horses have an LS gap (just in front of the high point of the croup as indicated) that is essentially in line with a line drawn from the top of one hip to the top of the opposing hip. This gives them the ability to transfer their power both upward (lifting of the forehand) and forward (allowing for full extension of the forehand and the hindquarters). Horse #3 shows an LS gap considerably rearward of the top of his hip, making him less able to transfer his power and setting him up for a sore back.
You may also notice that all three of these sample horses display an ilium side (point of hip to point of buttock), which is the same length as the femur side (point of buttock to stifle protrusion)—meaning that they produce similar types of power from the rear spring as it coils and releases when in stride. We can examine the variances in these measures in more detail in future articles, when we start to delve into various ranges of motion as well as other factors for soundness or injury.
Factors for Distance Preferences
The hindquarters of Horse #1 and Horse #2 also differ from that of Horse #3 based on the location of the stifle protrusion (not the actual patella, but the visible protrusion that one can watch go through its range of motion as the horse moves). The differences in stifle placement equate with range of motion of the hind leg, stride length and, to some degree, stride rate.
When it comes to the stifle placement for a champion at classic distances, we can see just how far below sheath level Tiznow’s stifle protrusion is and we can equate that to Lady Eli’s as well, even though she doesn’t have a sheath. Horse #3 has a stifle placement that is higher than the other two horses, more in keeping with the placement of a miler (at the bottom of or just below the bottom of the sheath). Sprinters tend to have stifle placement that is above that of milers.
The most efficient racehorses have a range of motion of the forehand that corresponds to the range of motion of the hindquarters. That may seem like stating the obvious, but not all horses have strides that match fore and aft. We have seen those horses that “climb” in the front as well as those that seem to “bounce” higher in the rump. In both cases, a mismatch of strides is often the cause.
For simplicity, let’s say the horse has to generate power from his hindquarters, transfer that power upward and forward through the spine as well as extend his front end at the same stride rate created by the hindquarters for efficiency. He/she has to maintain the same rate in the forequarters and the hindquarters.
One of the things we seldom think about is that horses have to move the front quarters at the same stride rate created by the hindquarters, but they do not necessarily have to be built to have the same stride lengths and turnover rates front and back.
If a horse has to significantly adjust the stride length fore or aft, he/she is likely not going to win in top company, especially racing. And for those horses that can adapt to slight discrepancies, a strong LS placement is paramount.
A car with different sized tires in the front than in the back will travel at a constant speed, but the smaller tires will rotate faster than the larger ones. A horse can’t do that, though; he/she has to compensate to bring the front and rear into the same stride rate.
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Spring 2019, issue 51 (PRINT)
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