Back / Lumbar

The spine is the bony structure between the head and the pelvis. It is the skeletal base of the trunk, located dorsally along the midline of the human body. It consists of an average of 33 bones, called vertebrae. Of these 33 vertebrae, 24 are « independent » and 8 to 10 are « fused ». They are divided into 4 distinct regions from top to bottom:

  • The cervical vertebrae (7: independent)
  • The thoracic vertebrae (12: independent)
  • Lumbar vertebrae (5: independent)
  • The sacrococcygeal vertebrae (8 to 10: fused)

The « mal du siècle », or back pain, is generally located in the lumbar vertebrae. The lumbar spine is made up of 5 vertebrae separated from each other by intervertebral discs. These discs have several functions: they absorb shocks and pressures from the spine, they play a role in the mobility and flexibility of the spine, and they also play a role in cohesion; they consolidate the spine and the vertebrae between them.

At the muscular level, it is the erector spinae or spinal muscles that are often linked to back pain. These muscles are often referred to as « lumbar » muscles in everyday language. They are a set of deep muscles that relieve pressure on the intervertebral discs. By contracting, they reduce the anterior pressure on the discs. They therefore play an important role in protecting the spine.


The spinal muscles or erectors of the spine are not limited to the lower back. They extend lengthwise on both sides of the spine. There are four muscle groups among these groups, 6 muscles are very important in this area.

In the transverse spinous group, we find the multifidus. Within the sacrospinous group, we find the thoracic longissimus muscle, the ilio-costal and the thoracic spinous.

Finally, the intertransverse and spinous groups include the interspinous and intertransverse muscles. These muscles are erectors of the spine and therefore responsible for self-erection. As extensors of the spine, they allow for the straightening of the trunk and control the ïexion of the spine. Finally, they control the inclination of the spine.

Function of the muscles


  • Controls the extension of the lumbar spine in trunk rotation
  • Role in the stability of the spine and control of its stability


  • Stretcher and extensor of the spine
  • Participates in the stabilisation of the costo-transverse hinge


  • Stretcher and extensor of the spine


  • Thoracolumbar hinge stabiliser


  • Stabilises the spine and helps control it
  • Extends the spine


  • Important role in maintaining posture by stabilising adjacent vertebrae during spinal movement.
  • Facilitates the action of other muscle groups in the back

The most common MSDs

Low back pain:

It is a very common MSD, characterised by severe pain due to the contraction of the back muscles and can lead to a blocked sensation in the back as well as difficulties in performing certain movements.

The sensations felt by the operators can range from simple discomfort to intense pain. The pain can also in some cases be felt in the upper buttock or thigh, so care must be taken not to confuse it with sciatica.

The erector spinae muscles are often involved in low back pain.

Herniated discs:

This pathology is located at the level of the intervertebral discs seen previously, each disc is made up of a gelatinous nucleus (nucleus pulposus) and has the role of absorbing the tensions undergone by the column.

A hernia is a protrusion of an organ or part, and a herniated disc is a protrusion of the intervertebral disc, most often in the lower back.