Horses Inside Out is on a mission to bust some common anatomical myths and misconceptions. As you know, you never stop learning, especially when it comes to caring for, training and riding horses, and its our passion to make learning fun and easy to understand. In this series we have been debunking a number of misconceptions - the ones that Gillian hears the most when she is lecturing on courses or presenting a lecture demo.
This next common misconception is one that we hear a lot but it’s an important one to discuss as it does cause quite a bit of confusion. With a clearer understanding, you will be in a much better position to help improve the horse’s topline, encourage the correct way of going so your horse is working over their back, improve the quality of work and their ability to carry the weight of the rider.
In this article, we are going to clear up the misconception about which muscles carry the rider. Many of you will be reading this and thinking, I sit on the horse's back when I’m riding, so it is the longissimus dorsi muscle that carries the weight of the rider. Now, that is true – to a point, yes, you sit on the longissimus dorsi, but it is not the muscle that lifts and rounds the back and therefore carries the weight of the rider.
Anatomy of the Longissimus Dorsi
Let’s start with another misconception, many think that the longissimus dorsi is a small muscle that is just in the area where we sit. This is because many pictures of muscles on horses show only a small area of this muscle underneath where the saddle goes. There’s a clue in the name – longissimus dorsi is in fact a very long muscle and you will be surprised just how far it goes!
This muscle doesn't just run along the length of the back, but it carries on further forward underneath the forelimb muscles and the scapula, attaching directly onto the fourth cervical vertebrae.
There are two other branches of longissimus dorsi, called longissimus capitis (capitis means head) and longissimus atlantis – referring to the atlas, the first cervical vertebrae. These two branches attach to the head and to the first cervical vertebra.
The main bulky part of this muscle comes from the fourth neck vertebra, attaching on to every single vertebrae all the way down the lower part of the neck, through the whole thoracic and lumbar region.
Continuing to the back end of longissimus dorsi in the lumbar region, there's the gluteal muscle, which comes over the top of the pelvis, and then we have the gluteal tongue, which attaches into the top part of longissimus dorsi.
As we move even further back, the muscle gets smaller, but it carries on further, through a small gap at the sacrum. The five sacral vertebrae are fused together and so are the transverse processes but there is a lateral ridge on the side of the sacrum, and then we also have the spinous process. Looking at that area in cross section, there's a right-angle shape, and the left and right sides of the sacrum form an upside down T shape. We also have the wings of the Ilium (part of the pelvis) that come up either side, and they come up to the top of the hindquarters at the point of croup creating the tuber sacrali.
We're not done yet - longissimus dorsi carries on both left and right sides underneath the ilium and above and to the sides of the transverse processes and through into the sacrum.
As well as this direct connection to the sacrum, the muscle continues, but becomes the sacrocaudalis dorsalis muscle, which is one of the muscles in the tail. Phew – that’s a very long muscle!
Muscle Atrophy
Atrophy is caused by discomfort or pain, which cause the muscle fibres to become less bulky and wither away. Sometimes, if you have atrophy of the longissimus dorsi, you can clearly see a hollow in the back where the saddle would be. Interestingly, if you also look in front of the scapula at the area above C4 and C5 you can get a hollow in this area as well. This is because, if we have atrophy of longissimus dorsi, it doesn't just show up in the back, it shows up in the neck just in front of the scapula too.
The Biomechanics of Longissimus Dorsi
Although the longissimus dorsi is the muscle under the saddle, its action isn't to round or flex the horse’s back. In fact, it does the opposite and helps to create extension in the horse’s back. Now, you might be thinking, hang on a minute, when I work my horse correctly, we talk about him developing topline. We need to understand more about the action of longissimus dorsi and that when this muscle contracts, it will create extension in the back.
Longissimus dorsi is a gymnastic muscle and is one of the largest muscles in the horse's body.
The main function of longissimus dorsi is to help transfer forces from the hindquarters forwards through to the rest of the body. You can feel this muscle working if you ride bareback. Alternatively, place your hand on your horse’s back and walk alongside him, you will be able to feel the longissimus dorsi contract as the hindlimb on that side pushes out behind him.
This muscle also has a number of different roles. It helps to:-
Create extension in the back, particularly if he's bracing or standing still, for example.
Transfer force from the hindquarters further forward.
Elevate the forehand when the horse is rearing, performing dressage movements when he shifts his weight back onto the hindquarters.
Elevate the hindquarters when he's bucking or jumping a fence.
What Muscles Do Support the Weight of the Rider?
Longissimus dorsi does not lift the middle of the back. If anything, overuse or an unbalanced use and the middle of the back will go down and cause extension in the back.
It’s actually the muscles underneath the spine that help to lift the back up. Longissimus dorsi is above the level of the spine, the vertebral bodies and the ribs, not underneath it.
There are NO muscles! directly attaching onto the underside of the thoracic vertebrae in the middle of the horse's back!
We've got the ventral longitudinal ligament on the other side of the thoracic vertebrae, yes, but in that region, no muscles until we go all the way down to the other side of the ribcage, and reach the abdominal muscles. These muscles when they shorten in length help to increase the pressure in the abdominal cavity, which can help lift the back up.
In terms of which muscles we need to be working on to help lift the back it’s not a matter of looking at the back itself, but the abdominal muscles and the chain of muscles that they're connected to. These include the hip flexors (the iliopsoas) and the thoracic sling muscles. Getting these muscles well-toned is going to help.
These muscles are the other side of the coin to the back muscles. The back muscles and the abdominal muscles work together, and it's important to have a good balance between the two. Sometimes, if there is a weakness from the abdominal muscles, the back muscles will try to take over. However, the back muscles aren’t very good at that role and that's one of the reasons why we see back problems in horses.
At some point in your life, you may have suffered from back pain. You go to see a physiotherapist and they advise you that strengthening your back won’t make the pain go away, but instead, you need to strengthen your core muscles.
Without abdominal muscles, there is no back.
Understanding this common misconception about the horse’s back and the muscles we sit on and support our weight is hugely important. From a welfare point of view, if we want to keep the horse’s back, happy, healthy and performing well for a long period of time, the focus needs to be on the core muscles and to use exercises that are going to be the best for improving the horse’s posture as well as their performance.
The abdominal muscles are the front of your horse’s back.
Building Core Strength
There are many effective exercises, both ridden and different Pilates style, in-hand exercises that will stimulate and strengthen abdominal recruitment.
A favourite has to be backing up. It's an exercise that all horses should do within their daily routine from a relatively young age. It is fantastic at preparing and maintaining their bodies for future and current ridden work.
It's not just about making your horse go backwards, you need to make sure that they're going backwards as well as they possibly can.
To hone your backing up skills and ensure your horse gains all the benefits, there’s a really useful FREE Tutorial Video available in the Horses Inside Out Academy. It's called Top Tips for backing up. You do need to be an Academy member to watch the video - it's FREE to join! Take the time to watch the video and observe how the horse's back moves having gained lots of new information from reading this article.
Online Learning
If you wish to further your knowledge in this area, there are a few on-demand recorded webinars that you will find informative and interesting.
As soon as we sit on the horse's backs we compromise his posture and ability to move and balance, as well as increasing the strain on joints, tendons and ligaments. It's vital to recognise how the horse supports posture and the musculoskeletal system.
From there you can look at ways to strengthen his body in preparation for a rider and performance.
This in-depth on-demand online lecture demonstration looks at Improving your equine partner's fitness, posture, strength and suppleness to future proof the body. It also looks at ways the rider can help to reduce the burden places on the horse's backs.
This on-demand webinar looks, in detail at the anatomy of the thoracic sling muscles and how to assess their strength. Discover which exercises will help to stretch and strengthen them.
This webinar is a must see if you wish to improve your horse’s posture and way of going or if your horse goes:
On the forehand
Pulls himself along rather than pushing from behind
Runs or is strong
Prefers a hollow outline or goes with a high head and neck position
Falls out through the shoulder
Struggles to maintain good balance
This on-demand webinar arms you with a clear and structured postural assessment system. It also looks at how we can determine what is good or bad posture and how through good management practices, in-hand exercises and correct riding, we can improve the horse's musculoskeletal comfort, longevity, flexibility and efficiency.
Gillian explains how good posture minimises the risk of muscular problems, back pain, muscle fatigue and injury. She also looks at how good posture is integral to helping the horse to carry the rider more easily.
Equine Anatomy Brought to Life
At our live painted horse lecture demonstrations we look at many of the common anatomical misconceptions. They are always great fun and bring the topic of equine anatomy and biomechanics to life and easy to understand. You will go home brimming with knowledge about how your horse works and armed with a host of new exercises to try with your own horse - plus a new found appreciation for just how amazing horses are.
Our next lecture demonstration is at Moulton College, Northamptonshire on Saturday 21 September. Book your tickets in advance and save £15!
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