Coupling, Back, Loin, and the Proportion Thereof in a Galloping Hound
I ran across an interesting discussion recently. The question was what was people preferred back to loin proportion in a sighthound? Did it vary by breed?
What immediately struck me was the variation in answers, even within the same breed. What remained constant? Borzoi. Every fancier and breeder who answered the question said 1:2 back to loin. Upon further examination, it became very clear that people in various defined back and loin in a variety of ways.
Borzoi people consistently defined back and loin using the same landmarks - the back was the thoracic vertebrae to the anticline (T11) and the loin was the remaining two thoracic vertebrae plus all the lumbar vertebrae. In more common vernacular - the back was from the withers to the anticline and the loin was from the anticline to the croup.
Why was it specifically Borzoi people who consistently defined the back and loin this way? In essence, because Dr. Anne Midgarden's Borzoi Speed Study. At the bottom of this post are links to all three studies. In these studies, Dr. Midgarden proposed various hypothesis as to which traits influence speed and then took measurements of actual Borzoi to test her hypothesis. Ultimately, throughout all three studies, what remained most constant was the biggest individual influence on speed was back to loin ratio. Specifically, Borzoi that had a back to loin ratio of 1:2 had the most speed.
Now, this brings up two questions. Why the fixation on speed specifically? And, is this applicable to all galloping hounds?
To answer the first question, Dr. Midgarden addresses the importance of speed in the first section of the first speed study.
Speed is the most critical feature of borzoi type and function, and it can be measured. It is more difficult to measure agility, desire and power.
If you have run your dog on live game, you understand the importance of speed. Ultimately, speed is what allows dogs to close and take game. You need agility, power, endurance and more, but speed is inherently important to all coursing hounds and is the most measurable.
As to the second question above - is this relevant to all galloping hounds? I have no concrete answer. There have not been studies in other breeds as there have in Borzoi. I know in Silkens, which used Borzoi as one of their foundation breeds half a century ago, they also typically looks for a 1:2 back to loin ratio. I have evaluated multiple litters where breeders were hoping for a sports prospect where the back to loin ratio was the deciding factor for the breeder with two similar puppies. I have also seen people who focus on dual purpose Whippets mention they look for a 1:2 back to loin ratio.
How about Azawakh? In general, they often have different proportions than most other typical sighthounds. I will say, in my experience, that most Azawakh with correct overall proportions (9:10 length to height, chest depth 40% of their height, etc) tend to follow the 1:2 back to loin proportions and those that do tend to have better speed than those who do not.
However, to accurately discuss back to loin ratio, we must first all be referencing the same landmarks. Below are three different ways that I have seen back and loin measured.
The first technique I have seen for measuring is measuring from withers to end of ribbing to define a dog's back and then from end of ribbing to croup to define the loin. While visually, this makes some sense, from a functional or anatomical standpoint, those landmarks don't have any bearing on back and loin. Beyond that, this actually includes some of the lumbar vertebrae as part of the defined "back". You will also note that when measured this way the defined back looks to be twice as long as the defined loin. It is important to discuss the flank - the space between the end of the ribbing and the croup - as this defines length of coupling, but we will discuss that at the end.
The next technique I have seen used is using the types of vertebra to define back versus loin. In this version of measuring you start at the first thoracic vertebra (T1) and end at the last thoracic veterba (T13). It is important to note, the anticlinal vertebra is T11. The anticline is where the spine essentially hinges and the vertebrae change the direction they're facing. This is true of all dogs, but it is critically important in sighthounds because it is part of what gives them their incredible colleciton and extension at a gallop. The thoracic vertebrae are the vertebrae ribs attach to, so the T12-13 vertebrae, while after the anticline, are still defined as thoracic because they have rib attachment. When measuring a sighthound this way, you will see that typically the defined back and loin appear roughly equal in length. Logically, this manner of defining back and loin makes some sense. Afterall, it is rooted in anatomical definitions. However, for the function of a sighthound the anatomical definition is less important than the functional definition.
Finally, I want to discuss how the Borzoi Speed Study measured back and loin: back is defined as withers to anticline (T1-T11) and loin is defined as anticline to croup (T12-L7). I would like to make a strong case for the importance of assessing coursing hounds in this manner. This is the method that utilizes structural landmarks that define the function of the dog at a run. The back is the part of the spine before the anticline and the loin is the part of the spine after the anticline and the definition of the two structural components is made at the hinge of the spine. It is when measuring dogs in this manner that you will see in most individuals of most sighthounds a 1:2 back to loin ratio, in my experience.
If many sighthounds have a 1:2 back to loin ratio, how does one account for the difference in their structure and appearance then? Naturally angulation of front and rear assembly can drastically alter structure, as can ribbing shape, sternum length, tail set, and many other factors such as shape of head and such. But what makes an Azawakh different from a Greyhound or a Silken when you are looking specifically at topline and their body? The answer is coupling. While Azawakh typically do fit the 1:2 back to loin ratio typical of most sighthounds, they are an extremely short coupled breed. Compare that to the moderately coupled Silken Windhound or the longer coupled Greyhound and while their back and loin keeps the same proportion, the structure of their flank is different.
I often seen coupling and loin conflated. However, coupling refers to a dog's flank - the area between the last rib and croup - rather than their loin. Most sighthounds tend to be longer coupled. As a general rule the more rectangular a breed is, the more likely they are to be long coupled (there are exceptions to every rule of thumb). More square breeds tend to be moderately to shorter coupled. Naturally, Azawakh, which are taller than long, are very short coupled. Longer coupling grants power and speed (the dog has a longer lever to get under themselves and propel forward) - though often dogs that are overly long coupled have weak toplines. Shorter coupled dogs have the ability to twist and turn on a dime, though they often have accordingly less speed.
One way I find helpful to picture coupling is to draw an ellipse between the end of a dogs ribbing before their croup. A longer coupled rectangular dog, such as a Greyhound, will have a horizontal oval.
A more moderately off-square breed like a Silken Windhound will still have a horizontal oval, but it will be less elongated.
Whereas Azawakh, which are longer than tall, are short coupled and typical if you draw an ellipse over their flank, it will be a circle, rather than an oval.
You'll note, all these dogs have close to a 1:2 back to loin ratio, but their coupling varies. And all are correct for their various breeds.
This is a nuanced topic. People are always going to have their own opinions, but these are landmarks and measurment techniques that I have found helpful in understand coursing hounds.
Below are some links to more information:
Borzoi Speed Study - Dr. Anne Midgarden
Spinal Structure - Stephane Hedgepath
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