The pecs – more important than you think
The pectorals are an important group of muscles that we tend to overlook. Understanding a bit about how to recognise dysfunction in this area can help us make better training decisions.
The pectorals can tell us a lot. Note the asymmetry between left and right.
When it comes to muscles in horses, we mostly talk about the muscles of the topline, maybe the muscles of the poll or the quadriceps, and that's about it. The pectoral muscles – the ones between the horse's front legs – don't get nearly as much attention as they deserve. But they are really important and knowing a thing or two about them can help you better understand how well your horse's training is progressing.
The pectoral muscles, which are sometimes divided into superficial and deep pectoral muscles, connect the front limb to the chest area. They originate from the sternum and attach to the front limb, making them a part of the thoracic sling. Because of the way they are positioned they play a big role in the horse's ability to lift the trunk up between the front limbs and to absorb the forces created during locomotion. If the pectoral muscles are working well, they act as shock absorbers, saving the lower limb from having to take up too much stress. What this means is that if the pecs aren't working optimally, the risk of lower limb injury is greater. So, you really, really want them to be happy and healthy.
How do you know when the pecs aren't working well? Dysfunction in the pectoral most often goes hand in hand with general thoracic sling dysfunction, so if your horse has trouble engaging through his thoracic sling, most likely his pecs aren't doing great either. Often, the pectorals can become very tight, causing the horse to stand narrower than he should. Tight pectorals can pull the front limb too close to the body, which can cause rotation in the limb, causing hoof imbalances. The girth line or the first rib area can become quite sensitive in these horses, so be careful when palpating this region.
As the pectorals become more functional, the horse starts to show a wider stance.
Tears in the pectorals (especially the transverse pectorals, just behind the elbow) are actually more common than you might think. Most of the time the owners are not aware of them, but they can cause thoracic sling dysfunction so it's important to address them. A muscle tear in this area usually heals pretty well, but it can leave the horse with some scar tissue which can limit the movement of the front limb and function of the thoracic sling. If this is the case, releasing the tightness and softening the scar tissue is the first step. This should be coupled with proprioceptive exercises and exercises to strengthen the thoracic sling. If the horse has been dealing with this for a while, the hooves will likely change too and might need some more attention during rehab time.
Next time we will look at some ways in which we can observe and palpate the pectorals to get an idea of whether or not they are functioning properly.