Chain of muscles – The muscles of the back and abdomen work together giving protection to the spine, allowing it to lift and flex, creating motion. For the horse to flex its back it must contract his abdominal muscles and relaxing the muscles will allow the horse to lengthen its back.
When the rectus abdominus muscle contracts this exerts positive force on the sternum and pelvis causing flexion at the sacro-illiac joint and the lumbosacral joint. As the pelvis tilts this allows the horse to reach further forward with his hind leg under his belly. This reaction curves the spine upwards and creates impulsion in the strides.
Initially in the horses training the focus is on rhythm and strengthening the muscles for pushing off the ground. As the horse develops through correct training the increased pushing power of the hind limbs can easily push the horse onto the forehand and so the muscles in the forelimb must maintain the elevation and as the training continues the horse develops further ability and muscle strength in the hind limbs and over its back. For a muscle to improve in tone and strength it must go through activity that stimulates more than 75% of the muscle fibres in maximum tension or stretch to stimulate growth.
Strong muscles stabilise joints and reduce strain on tendons and ligaments which help protect against injury. It is important to know that when muscles are tired the horse must be rested otherwise other incorrect muscles will come into play or the original muscles will be overloaded or injured.
Horses ridden incorrectly, out of balance or with a poorly fitting saddle, hollow their backs away from pressure and in doing so relax their abdominal muscles which become weak, do not work together with the topline muscles. This has extreme consequences for the horse as the spinal processes will collapse towards each other which in turn can become the dreadful condition of kissing spines where the spinal processes jam together causing pain, inflammation, swelling and pressure on nerves. The spinal processes can fuse together causing a permanent loss of motion.
Written by Sam Jamieson © 2015