Assessing the pectoral muscles
The pectoral muscles can become tight with thoracic sling dysfunction, lower limb injury or hoof imbalances. Here are a few ways to check if your horse’s pecs are in trouble.
Slide your hand (gently!) between the scapula and the ribcage. There should be plenty of room here. If you feel like the elbow is in the way, the pecs might be tight.
Last week we talked a little bit about the general importance of the pectoral muscles. This week it's time to look at how we can assess them in order to know if the horse is using them properly or not. Just a general warning, some horses can be a bit sensitive in this area, so approach the pectorals with caution, and make sure to be polite when palpating. Ok, here we go.
First, let's just look at the horse. Observe him from the side. If you can see a dip in front of his withers, if the underside of his neck is developed more than the top of his neck and if he is standing way too far underneath himself with the front legs, chances are his thoracic sling (and with it, his pectorals) aren't working properly. Then look from the front. Do the muscles on the left and right side of the sternum look symmetrical? Often there is asymmetry in the pectoral muscles, which can mean the horse has a hard time using both his front legs in the same manner. Obviously, that is not what we want. Is the horse standing base narrow? Tight, restricted pectorals can cause the horse's chest to appear narrower than it should be, making him stand base narrow. Often, youngsters will have a poorly developed neck and a narrow chest. This is normal, but it needs to change with training. I suggest you take photos from the side and the front, to keep track of your horse's progress.
Next, let's palpate the muscles. Find the sternum and palpate from the edge of it to the left and then the right pectoral muscle. Be gentle at first and then palpate a bit more firmly on each pass. If the horse shows signs of discomfort or if the muscle feels hard to the touch, the pecs might be in trouble. Then palpate from behind the scapula. Find the point of elbow and see if you can slide your palm between the elbow and the ribcage. Go slow and stop if the horse isn't comfortable with it. If the pecs are working well, you should be able to slide your palm all the way in. If not, this will feel impossible and you will get the feeling that the elbow is “glued” to the ribcage.
Palpate the pectorals just off the sternum.
The third thing to do is to assess movement in this area. Pick up your horse's leg as if you were cleaning his hooves. Stay there for a while until the horse relaxes. Keep the angle of the carpus around 90 degrees and place one of your hands on the lower part of the scapula. Using the hand on the scapula, rock the leg backwards a couple of times. If the leg seems stuck and doesn't easily rock, the range of motion in this area is limited. There could be several reasons for this, but very often this will go hand in hand with tight pectorals. Then, bring the leg forward and allow the horse to relax it towards the ground. We are looking for a slow, controlled lowering of the leg, not a jerky movement. You should see the point of the elbow slowly dropping downwards. If the horse can't do this, chances are his pecs (and other muscles of the thoracic sling) are tight.
Pick up the leg and rock it backwards. Does this feel easy or restricted?
This should give you a brief overview of how to assess the pectoral muscles. If you came to the conclusion that the pecs might be dysfunctional (or if you are not sure), it might be a good idea to call a professional to help you make a plan for returning functionality to this very important area of the horse's body.
Associated content:
The pecs – more important than you think