The serratus ventralis muscle can be split into two sections, the cervical and the thoracic.
Origin: from the scapula cartilage.
Insertion: into the last 4-5 cervical vertebrae.
Function: This portion of the muscle is responsible for the backwards and forwards movement of the scapula and therefore moving the limb.
Origin: Underside of the scapula and the intercostal fascia.
Insertion: Across the 1st to the 9th ribs.
Function: This portion of the muscle is part of the thoracic sling which acts to suspend the horses chest between the forelimb and is important in the moment of suspension in the horses natural forelimb movement and lifts the ribcage.
Soreness: The main causes of tightness in this muscle can arise during jumping from the concussive forces of landing and poorly fitting saddles which can restrict shoulder movement. A horse that is tight in this muscle may have a shortened stride, reduced scapula movement, girthing issues, difficulty turning on the forehand, and potentially poor respiration due to the location of the thoracic section where tension may reduce ribcage expansion.
Chin to fetlock carrot stretches can help to stretch the serratus muscles and increase flexibility in the neck and the shoulder blade.