Therapeutic Exercise Influences on Activity of the Multifidus Muscles in Horses

Back pain is a worldwide debilitating condition that affects humans and animals alike. Lower back pain in humans can be caused by a myriad of conditions, including idiopathic origin. Spinal stability is compromised during disease, and a lack of stability also contributes to pathologic spinal conditions. Regardless of species, the stability of the spine depends on bones, ligaments, tendons and muscles. Muscles provide the only active component that can counteract various loads applied to the body. There are several muscle groups that contribute to spinal mechanics. The erector spinae group are large superficial muscles the lie along each side of the spine and traverse its length. The erector spinae muscles are responsible for major trunk motion in all planes. Motion in the lumbar spine primarily consists of flexion and extension, but also partially contributes to lateral bending. The multifidus muscle group is deep to the erector spinae group and is responsible for postural maintenance of the spine. The multifidus also traverses the entire length of the spine, however its attachments are organized in small bundles or fascicles that only cross a few vertebral levels. Therefore, it is responsible for small finite movements to promote vertebral alignment. In humans, the multifidus is thought to be the main spinal stabilizer.

Spinal disease is associated with alterations in both the erector spinae and multifidus muscle groups. It has been difficult to determine if changes in the muscles alter stability and allow for disease, or if spinal disease induces pathology in the muscles. The majority of muscle changes consist of atrophy and or fat infiltration, both of which compromise the ability of the muscle to produce force.

Human physical therapy strategies have focused on stretching and strengthening both the erector spinae and multifidus muscle groups. These protocols have been extrapolated to quadruped animals without justification or knowledge of the biomechanical function of these muscle groups in quadrupeds.

Overall, we determined that the average and peak levels of activation of the multifidus muscle was increased on soft impressionable footing, while incorporating ground poles, and without the use of the tested training device, in trotting horses.