Sitting and Standing Activities as a "Pain Generator" in Lower Back Pain

Many studies show that lower back pain (LBP) is one of the biggest causes of disability in the world. About 80% of the population experiences at least one episode of LBP in their lifetime. This condition can interfere with daily activities, and have an impact not only for physical but also psychological. Statistical data shows that about 76% of patients complain of LBP when sitting activity, and about 70% complain when standing activity. The data illustrates that simple daily activities such as sitting and standing can trigger LBP symptoms. In scientific terms, activity as a trigger for one of the symptoms in an illness is often called a “pain generator”. As in this article will discuss how the activity of sitting and standing as a pain generator in LBP.

LBP is a pain syndrome that occurs in the lower back region and is a work related musculoskeletal disorders. The most common cause of LBP is muscle tension caused by improper posture. Things that can affect the onset of LBP are sitting activities, prolonged bending, lifting weights with an un-ergonomic attitude, abnormal spine, or due to certain diseases such as degenerative diseases.

Anatomically, it can be imagined that the lower back of the spine, called the lumbar vertebra, is a pile of short tubular segments where there are several supporting structures both in front and behind the spine. In the back, between these segments, there are small cavities on the right and left sides of the segment called the intervertebral foramen as a place for the pair of nerve roots to emerge from the spinal cord. Behind the segment, there are a pair of facet joints that provide the movement in the spine. At the front, between one segment and another, there is a soft structure called the intervertebral disc as a cushion that can absorb the force that applied through the spine. Under normal conditions, the piles of these segments are not straight, but rather form a convex curve on the front side and concave on the back side called the lordotic curve. This curve is flexible which always changes with changes in body position.

Simple activities like sitting and standing influence how the shape of the curve in the lumbar vertebra. In the upright activity, the lordotic curve in the lumbar vertebrae will increase and vice versa, sitting activity reduce the lumbar vertebral lordotic curve by approximately 50% which causes the loss of the normal curvature of the spine to become flat which is often referred as flat back. If the decrease is more than 50%, the lordotic curve will reverse towards a kyphotic curve which is a convex curve on the back side and concave on the front side.

Based on simple laws of physics, an object that is bent, will produce two forces together, namely the compression force on the side in the direction of the bend, and the pulling force (tension) on the opposite side of the bend direction. Increased lordotic curves in the spine during standing activity produce compression forces on several structures in the back, such as the facet joints and intervertebral foramen (as well as the slackness of the back musculature), and the pulling force (tension) on structures in the front such as the intervertebral discs. And conversely, the reduced spinal lordotic curve during seated activity results in compression forces in the frontal structures such as the intervertebral discs and traction forces in some structures in the back such as facet joints and intervertebral foramen (and stretched back musculature).

Based on this understanding, the activity of standing and sitting as a pain generator on LBP can be seen in the following tissues: 1) Para-spinal muscles - Sitting activity reduces the lordotic curve which will cause the extending of the paraspinal muscle located behind. Prolonged stretching for a long time will trigger lower back pain; 2) Facet Joint and Intervertebral Foramen - Standing activity increases the lordotic curve which will produce compression on the facet joints and intervertebral foramen. When a process of inflammation of the joints occurs, the compression force will trigger pain in the lower back that experienced in a long standing activity; 3) Intervertebral discs - Intervertebral discs are compressed when the lordotic curve is reduced. Excessive compression of the intervertebral discs to the point where there is a herniation in the tissue inside, may compress the nerve roots behind it and cause pain radiating from the lower back to the legs. In this case, long sitting as a pain generator and standing activity tend to reduce symptoms.

Based on the explanation above, both sitting and standing activities can exacerbate complaints on LBP caused by compression or pulling force. Sitting and standing activities can help identify a number of tissues as pain generators in the LBP as well as help in choosing the right education for LBP conditions.