By Sue Reive
Ever wear a pair of loose pants without a belt? You feel like you are letting it all hang out! This is what happens when your abdominal muscles are weak; indeed, the abdominal muscles, specifically the transverse abdominis, are like the buckle on your belt. When they contract, they help stabilize your trunk, which is necessary for everyday activities. Many people suffer lower back pain because they lack strong core muscles, i.e., the deep back muscles and abdominals.
The spinal column consists of 33 vertebrae, of which 24 are moveable. They are connected by discs and ligaments allowing both movement and stability. The discs consist of a ligament-like outer ring which houses a soft gel-like inner nucleus. The discs act as shock absorbers but at the same time allow spinal movement, while adjacent ligaments help to stabilize the vertebrae.
There are seven vertebrae in the neck (cervical), 12 vertebrae in the thorax, to which the ribs attach and form the ribcage, and five vertebrae in the lumbar spine. The remaining vertebrae are fused together to form the tailbone (sacrum and coccyx).
The vertebrae sit on top of each other and form a distinctive S curve with the neck and lower back being slightly concave and the thorax convex. These curves help the spine to withstand the force of gravity and loading; any deviation from the normal S-curve will reduce the spine’s ability to shock absorb and transmit load.
The surrounding spinal muscles provide the stabilization necessary for a healthy spine. The spine has muscles that move the spine forward (flexion) and muscles that move the spine backwards (extension).
The extensors keep us upright. There are three layers of back extensor muscles: the most superficial muscles include the powerful latissimus muscle; the middle layer consists of the erector spinae muscles which keep us erect; and the deepest muscles include the multifidus, which functions to prevent excessive movement of the spinal joints. The latissimus and erector spinae muscles function as prime movers and are responsible for large spinal movements such as bending and generating power for activities such as shovelling.
In addition to the muscles, the thoracolumbar (TL) fascia, a diamond-shaped ligament-like structure, provides core stability. It covers and surrounds the lower back muscles (multifidus, erector spinae) and serves as the attachment site for the large buttock muscle (gluteus maximus) and the latissimus and trapezius muscle in the neck and upper back. Thus, the TL fascia helps transfer the force between the arms and legs. The abdominal muscles in the front (transversus abdominus) attach to the TL fascia. When the abdominals contract, they pull on the TL fascia and help support and stabilize the spine. It is like tightening the buckle on the belt.
The ligaments, discs and deep muscles send messages to the brain about joint position. The nervous system then makes specific muscles contract to maintain trunk stability. The deep muscles are extremely important in stabilizing the vertebrae during movement. Sometimes people have good core muscle strength but poor motor patterning; they exhibit what is referred to as a faulty movement pattern and therefore lack stability.
Some people have spinal segments with increased spinal joint movement due to injury or lax ligaments. One such example is anterolisthesis where one vertebra slides forward on the adjacent vertebra. This causes more stress on the spine which leads to pain and dysfunction.
Spinal stability requires good alignment of the vertebrae, good strength in the spinal muscles and correct muscle control by proper firing of the nervous system. Treatment focuses on strengthening and motor patterning.
Without good spinal stabilization, lower back pain can ensue, and simple activities of daily living become difficult. So, take care of your spine and start a good strengthening program.
Susan Reive is a physiotherapist at Ottawa Physiotherapy and Sport Clinics – Glebe.