M. Cutaneus Trunci in relation to saddle and girt
Dissections of 12 horse cadavers showed that m. cutaneus trunci is more variable in shape and size than anatomical books imply. The muscle lies beneath the weight-bearing panels of the saddle and the girth in all horses, with the thickest part being directly under the girth and the rider’s leg.
Tactile stimulation of the skin behind the triceps or pressure along the girth line may give ongoing reflex muscular contraction of the cutaneous muscle. Horses that show signs of resentment while saddling or girthing may have learned to react to this nociceptive stimulus that initiates the panniculus reflex.
The muscle was considerably large, weighing 2.6- 4.3 kg and having a 1.5- to 2.7 cm thickness in the girth region. In the scapulair region it was stuck to the underlying fascia (craniodorsally). On the ventral side m. cutaneus trunci was attached by fascia to the tendons of m. latissimus dorsi and m. teres major on the teres major tuberosity and the glenohumeral joint capsule. See figure.
Horsemanship books recommend to protract the forelimbs after tightening the girth to stretch out wrinkles of the skin underlying the girth. Because of the fascial attachment of the cutaneus to the humerus, it is likely that forelimb protraction stretches the fibers of m. cutaneus trunci resulting in a reflex muscular relaxation. Therefore, forelimb protraction may break the cycle of persistent muscle stimulation and relieve the horse’s hypersensitivity to girth pressure.
>A. van Iwaarden et al.,Journal of Equine Veterinary Science 32, 2012, p 519-524. All rights reserved to 2012 Elsevier Inc.