The loin is arguably one of the most important structures in the horse. It is inherently weak in its design, being a freespan (having no ribs to add support and strength), and therefore is susceptible to injury. The loin of the horse is equivalent to the transmission of a car; it transfers power created by the haunch (engine) forward. A mismatch of a powerful haunch (engine) to a weaker loin (transmission) all but guarantees ‘spinning tires’ and often structural failure.
To put it in simple terms;
- The shorter the loin is in length, the more strength it possesses.
- The deeper the loin, the more strength it possesses.
- The broader the loin, the more strength it possesses.
The strongest loin is therefore a short, deep, broad one. This type of loin is virtually indestructible and guarantees full transmission of haunch power brought forward, but can produce a rough ride if it gets muscle bound. Think of it in terms of a body builder with their massive strength, but often times lacking flexibility. A horse with this loin absolutely must have a training focus on creating and maintaining suppleness. Of course we now know that how far the ribcage carries back plays a role in lateral flexibility. A short loin guarantees ribs that carry back well for lateral flexibility, so the potential for suppleness is clearly there with a short loin.
The weakest loin is a long, shallow, narrow one. This type of loin is highly susceptible to damage. It can combine with other traits to make a rather smooth ride because the horse that possesses it often hollows the back and becomes a leg mover, but invariably it breaks down under anything but the lightest of workloads.
Six lumbar vertebrae make up the loin.
There is no specific loin measuring system in terms of garnering a specific percentage. We use various body references to determine its length.
1) The ‘quick and dirty’ hand measurement discussed in the Part 2b – Ribcage article. Greater than a spread hand’s width (8″) and the loin is long; about a spread hand’s width and the loin is medium, and less than a spread hand’s width and the loin is short.
2) The loin should ideally be as deep as the chest. A significant difference and a loin is very likely long. Note: Excellent riding and training can deepen and strengthen a loin.
3) The further behind the point of hip that the LS joint is, the more likely the loin is long.
4) Probably the most telling view for the loin is a top down view. Marking the points of hip, the LS joint and the first lumbar vertebrae, then connecting the points (minus the LS joint) will produce a triangle. An equilateral triangle with the LS joint inside the base line would be a short, broad, deep and strong loin, whereas an isosolese triangle is going to indicate a longer, less broad, less deep and therefore less strength.
Let’s take a look at our six horses, concentrating on their loins.
Horse #1 – QH stallion: This is a short loin with great depth. We don’t have any overhead shots of our horses, but if we did this horse would also be broad across his loin. Our horse with the biggest hip has a loin of more than sufficient strength.
Horse #2 – QH gelding: This loin is longer than our first horse because the LS joint is placed further back. If it was placed in the same location as our first horse, the loins would be identical. Still this loin remains medium in length and has excellent depth and breadth.
Horse #3 – 4yr old QH: This loin is also medium in length, but just. It’s not as deep as our first two horses, but likely possesses good breadth.
Horse #4 – Arabian Stallion: Another short, solid loin. It lacks a bit of depth, which I blame on the table top croup preventing engagement.
Horse #5 – TB Gelding: The shortest loin of our group. It has good depth (don’t let the distended belly fool your eye). This is another one that likely isn’t particularly broad and thus why it isn’t as deep relative to the shortness.
Horse #6 – Paint mare: Here we have a long loin that lacks significant depth and likely breadth as well. This is a highly susceptible construction and we can be thankful that she doesn’t possess the same kind of hip as our first three horses or she’d be in big trouble.
Based on what we have analyzed so far; hip, back, loin, lumbo-sacral joint, ribcage, to a lesser degree the withers, and setting aside any personal or breed biases, or anything else we might know or suspect about the individuals in question, how must this group of horses be ranked? Before you peek, think about it. Which horse at this stage seems to have the most athletic potential AND ability to stay sound through the back and loin doing whatever task they may be asked in the future…all other things being equal and relative. And who appears to have the least? And why?
In reverse order:
6. Horse #6, Paint mare. Her back is long, her loin is long, her ribcage does not carry back well, and neither do her withers. She possesses adequate hip length and might very well produce some easy gaits to sit to by means of hollowing the back and being a leg mover. Of the group, this horse requires the most knowledgeable rider to prevent topline breakdown and improve its strength.
5. Horse #4, Arabian Stallion. There is just no getting around the table top croup, it’s just that severe of a fault and the camel withers don’t help. What saves this horse from breaking down through the topline are the shorter back, the short loin and the ribcage that carries back well, all of which add significant structural strength. While this is no novice ride, this horse is far less likely to succumb to topline breakdown from hollow riding than our Paint mare. For that reason he garners one spot up from the bottom.
4. Horse #2, roan QH gelding. Simply based on having the poorest LS joint placement of the remaining candidates, increasing the difficulty of engagement.
The next two placings are very close and arguments can be made for switching them based on discipline and type of issues a person prefers to deal with.
Tie for 2nd – Horse #1, QH stallion and Horse #3, grey QH gelding. Our stallion is shorter backed, has a short, deep, broad loin, a huge hip, a good LS joint placement, and ribs that carry back well giving us super longitudinal strength, super power potential, super potential to engage, but perhaps lacking a bit of lateral flexibility through the body compared to the grey gelding with a longer (yet still medium) back, a medium loin (that does lack a bit of depth), a big hip, a very good LS joint placement and ribs that carry back well. His withers aren’t as well defined or designed, but still functional. This one may possess a bit more flexibility, but also may tend to evade through the body more. Still plenty of power and engagement ability, this one might very well ride a bit smoother.
1. Horse #5, TB gelding. The horse with the least hip length currently heads our list because there is so much strength in the rest of his topline that that lack of pure power can be overlooked – as long as we’re not going to ask him to be a sprinter, or an International/GP competitor. He has a great short loin and LS joint placement, withers and a ribcage that carry back really well to add longitudinal strength to the medium back and should possess a good amount of lateral flexibility as well. This horse should present as the most viable individual, for the most people, with the widest range of knowledge and ability. There is not so much power or movement potential that a beginner/novice couldn’t handle this horse, and yet there’s enough longitudinal strength to protect the horse against that sack of potato rider. Additionally there’s plenty of lateral flexibility and engagement potential that a more advanced rider could also enjoy this topline. For those reasons this horse takes the top spot – for now.
We’ve only just begun our analysis of this group of horses; there’s so much more to look at and consider. I suspect *wink* that the current rankings may change as we delve deeper into the conformation of these individuals. Will your original choice end up at the top of the list? (Insert appropriate musical cue) Stay tuned for the next series of articles discussing body levelness and shoulders.