Quo vadis, Pectoralis? - Hands for horses

Quo vadis, Pectoralis?

Social media offer a wide-variety of information. Many therapists use social media to provide information about their work and knowledge. While this is an opportunity for interaction and learning, it also has its challenges because the information is not peer-reviewed and often wrong or deceiving. Half-correct facts spread easy and fast with the consequence that more people share this false information. Especially if therapists implement the wrong information in their therapy patients might get harmed.

The other day, I stumbled over an article about equine M. pectoralis group.

In this statement it says that a tense pectoralis muscles may originate from a mare in heat, when problems with the digestion are present and during breathing problems. Even a girth that annoys the horse creates tensions in the pectoralis muscles. “Feeling”-receptors are extremely sensitive then and it occurs very easy edema. Sensitivity becomes obvious when the horse changes its behavior and is annoyed and volatile. Those muscles should be given a careful massage, with light pressure. In the end, they also warn to be aware for histamine reactions and sweetening which might upcome with massage of this area. (as a rough citation of the original Swedish article).

Interesting facts about the pectoralis muscle in horses

Since horses have no collarbone, they lack a bony connection between their front limbs and the trunk. This gap is filled by a strong muscle group consisting of the serratus ventralis thoracis and the pectoralis muscles. They connect the inside of the shoulder to the rib cage, and act like slings and suspend the chest between the front limbs of the horse. Contraction of this muscle group raises the withers to the same height or higher than the croup resulting in an uphill motion with a reduction of the load on the forehand. If your horse has problems in the pectoral area, it might throw his head up when transition to canter.

Now, coming back to the contribution I found:

It would be important identifying the pectoralis muscles described. According the textbook „Anatomie der Haustiere“ (Anatomy of the house animal“) the pectoralis muscle separates into the superficial and deep muscle groups. Furthermore, the superficial pectoralis muscle divides into three groups of muscles bellies (ascendens, transversus, and descendens). The pectoralis muscle participates in the movement of the front leg, acts on the and the shoulder joint and the body of the horse. The function of the muscle groups differs and tension in the muscle may originate from many sources. To identify the cause for the increased muscle tension will be difficult.
A careful search of available literature from scientists and clinically trained, we have found no evidence for a correlation between estrogen levels and tensions in pectoralis muscle group. The same holds for a correlation or causal connection between pectoralis muscle tension and breathing or digestion problems.
The only fact established in the literature is that in rare instances mares show increased sensitivity in their lower back during the development of the follicles. However, there is no mention or evidence for a tense pectoralis. One rare scenario could be considered: a mare in season, with a lack of force in the hindquarters, a hypersensitivity of the back muscles may stress the pectoralis muscle.
Factors that might contribute to superficial pectoral or subclavius muscle hypertonicity is lower neck pain and forelimb lameness. Girth pain related to cinch or girth tightness or wear often affects the deep pectoral muscle.

How edema develop

Edema originate from an imbalance between fluids leaking from the blood vessels into the tissue and fluids taken up by the blood vessels and fluids removed via lymphatic drainage. While balanced in a healthy body (person or animal), changes in blood proteins, changes in blood pressure, blockage of the lymph drainage, increase in the venous pressure, or inflammation can disturb this balance and result in fluid accumulation in the affected area. Edema are typically seen in subcutaneous tissue as swelling. Gentle pressure leaves visible indentations. The muscle is typically not target for edema.

What about sweating

Local sweating is a sign for enhanced local circulation caused by the release of histamines through the action of interleukins. This histamine release is a natural reaction and should not be confused by histamine release following rigorous massages engaging shear movements and resulting in local tissue damages. Therefore, if horses show local sweating during massage treatment, it is a good sign because it reflects stimulation of the sympathetic nervous system and sudomotor responses. There are some important sympathic ganglion at the base of the neck that might be affected with deeper massage techniques.

The girth pain syndrome

Girth pain syndrome is the most common problem if a horse shows with a tense pectoralis muscle group. In this case I recommend the rider to saddle the horse, set the girth in the lowest hole and drink a cup of coffee or just wait a while. In addition, the rider can before laying the saddle on the horse, perform gentle tapping the area to decrease the sensitivity in this area (it could even be the sensitivity of the horse’s skin). If this approach fails, a closed examination of the trapezius muscle after saddle mount is indicated. The muscle which is often hypertonic or shows sign of atrophy. It is advised to control the saddle position. However, do not pad if an atrophy of the trapezius muscle has been established.