05/18/2025
Atrophy in top lines and performance horses.
Soundness in veterinary science is judged by the horses ability to balance evenly across all four legs, when one leg is sore it presents in a lameness. Traditional one leg lameness is easy to spot, head bobbing and a definite asymmetry in stride. This will definitely be identifiable as lameness in the trot ups for competition and should be pulled up. That being said I am often seeing assymetric movement be passed off as sound. This is soundness grey area, assymetry in my opinion is the stage before lameness, the body is protecting a weakness that is yet to develop to the lameness. Assymetry can be from a plethora of problems from soft tissue to skeletal and very few of these problems are identifiable through imaging for horses. Unless it’s in a distal limb and I would argue that is often a red herring for an issue higher up.
Where it starts to get very tricky is body lameness, one pathway for body lameness is atrophy of muscles but why does it happen? Two main reasons, either the muscles aren’t utilised or the muscles have lost intervation by the nerves. If you’ve never googled “sweeny shoulder”, a common injury in Thoroughbreds I suggest you do that to see how nerves affect muscles. The delicate nerves and vascular systems in the horses body are all
Interconnected, I don’t like to focus on one area because the horse is ONE body. But for efficiency I’ll focus on a few, the trapezius(cervical and thoracic) waste away when horses are ridden on the forehand and behind the vertical. The trapezius is also affected by saddle fit and can impede the shoulders movement, the scapular cartilage is often damaged in horses with poor saddle fit.
Logissimus dorsi, affected by riding behind the vertical and hand dominated posture that impedes lateral spinal movement, easily atrophied if worked in tension.
Multifidus is an over looked muscle group in the back, it has a massive impact on DSP spacing due to the way it attaches and can pull DSPs towards each other(kissing spines) this muscle group can be protective or destructive depending on how you condition them. There are many more important muscle groups I will go in to detail in my book.
The main thing to remember about muscles is they are extremely compliant to their loading, meaning they either develop or atrophy. Just look at the huge range of development in humans, a ballerina and a body builder are both athletes but have developed their bodies in radically different ways.
Competitive eventing horses are judged on two things, their soundness in the trot ups and their ability to complete the three stage course, Dressage, cross country and showjumping. Horses who display atrophy in their top lines, will do dressage behind the vertical, be heavy in the riders hands and movements on the forehand. You don’t need a great topline for this Level of dressage, you can carry your horses front end and still score well enough. Horses with atrophy will display big lofty scope on the cross country to clear fences utilising both speed and hind end power. You don’t need a great top line for cross country. Where atrophy will bite you though is in the showjumping, because you do need healthy top lines to be able to either shorten or lengthen a stride to a show jump. You do need the horse to be up and off the forehand to lift the front end because unlike cross country you can not run at a show jump flat and fast. Show jumping is the leveller in eventing at high level because the fences aren’t solid and clever horses get sloppy knowing they can drop rails with hanging shoulders and lazy hind legs. For a good show jumper you need a horse who can collect well, not just be held together by the rider. This is the stage where healthy toplines matter, whether riders know it or not…..a young horse may get away with it but horses over 10 years old wont have elastic youth on their side.
The horses topline tells me everything about how that horse works, when muscles are atrophied they arent working…..it’s that simple.
Year after year we see these horses in the trot ups and the internet goes wild. Soundness and what can be proven are two very different standards. Vetrinary science is built on a peer reviewed, rigorous and reductive method but I feel the problems are more nuanced than science can explain currently. I see horses in dissection constantly that I’m amazed haven’t just laid down and died. Horses that shouldn’t let humans ride them from massive internal issues. Every single one of those horses displayed behavioural issues that were passed off as quirky, naughty or being difficult. I would argue that competitive horses have the mental grit to do the job even with sub par bodies, they are the David goggins of horses! The argument is that david was self aware enough to understand the impact on his body long term and we expect this servitude from the horse without them understanding the impact.
The argument for top line atrophy and performance is “they wouldn’t be able to do it if their bodies were ruined” unfortunately the evidence I see in dissection is the complete opposite. Horses will endure incredible hardships because they are wired as prey animals with the most incredible survival instincts and competive horses have extreme mental
Fortitude. I dont have any judgements or answers, what you do with your horses is your business but I believe in education and understanding for the things we are yet to learn.
The body keeps the score
