Sitting posture and lower back pain

Abstract:

An imbalanced lateral bend becomes a static posture.This article analyzes the relationship between the shift of the center of gravity in sitting posture and lower back pain.

1. This article analyzes the relationship between the shift of the center of gravity in sitting posture and lower back pain.
2. In a proper sitting posture, the spine is centered and maintained by the coordinated effort of the abdominal oblique muscles and the erector spinae muscle group.
3. When the center of gravity shifts towards one side of the buttocks while sitting, the balance of the four major abdominal oblique muscle groups is gradually lost.
4. The imbalance of the large muscle groups forces the smaller stabilizing muscles around the spine to work excessively to maintain stability.
5. The overworked small muscles lose their elasticity over time, leading to a lateral shift of the lumbar spine.
6. Once the spine is laterally displaced and compresses the nerves, it can cause pain, numbness, and even incontinence.
7. Professional assessment and targeted training are recommended, or one can try to adjust the center of gravity in the sitting posture.

In the previous discussion, we talked about how prolonged compensation by unilateral small muscles can eventually lead to injury. Due to the inability to make fine adjustments, the joint will inevitably deviate over long periods of imbalance. Prolonged unilateral sleeping, unilateral exercise, and side-leaning when using computers or watching TV can easily cause excessive spinal rotation to one side, resulting in lower back pain.

In this episode, we discuss common sitting postures in daily life, such as crossed-leg sitting, single-leg resting, desk work, napping while lying down, single-hand phone holding, leaning on chair armrests, and single-leg driving. These unilateral, prolonged sitting postures can lead to a shift in the center of gravity to one side, causing lateral spinal curvature and lower back pain.

Please simulate the above sitting posture and feel the pressure on your buttocks. Are both sides the same?

In the above sitting posture, the center of gravity is shifted to the left side, and the pelvis is tilted to the left. If the spine does not curve laterally, the body will lean to the left side.

When the pelvis is laterally tilted, the lateral curvature of the spine can occur in any region of the lumbar, thoracic, or cervical spine. This can result in a C-shaped curvature or a combination of multiple C-shaped curvatures, forming an S-shaped curve, as shown in the picture below.

How the spine moves in lateral bending

In our daily lives, we need the function of lateral bending of the spine, such as when getting dressed, lifting heavy objects, and playing sports.

The main muscles involved in the lateral bending of the spine include:

• The external oblique and internal oblique muscles of the abdomen
• The erector spinae muscle group in the back

The muscle fibers of the unilateral (single-sided) internal and external oblique abdominal muscles are angled outward towards the sides of the body. The fibers of the internal and external oblique muscles run in the opposite direction.

During lateral bending of the spine, the backward and forward forces generated by the ipsilateral (same-sided) internal and external oblique muscle layers precisely counteract each other.

The net combined force acts to bend the spine downward and to the side.

The erector spinae muscle group is attached to the sides of the spine, maintaining the stability of the spine. They work in coordination during lateral bending of the spine.

An imbalanced lateral bend becomes a static posture.

Any movement involves certain muscles actively contracting while others are passively lengthened. During right lateral bending, the right internal and external oblique muscles shorten, while the left ones lengthen. The opposite occurs during left-lateral bending. If the time and force of left vs. right lateral bending are relatively balanced, the contracting and lengthening muscles can achieve alternating regulation and balance. However, if one side is favored long-term, the contracted muscles become stronger while the lengthened muscles weaken. This muscle recruitment habit then carries over to other postures and movements, with the stronger muscles being recruited first, faster, and more forcefully, leading to an imbalance of muscle forces.

From anatomical diagrams, we can clearly see that the cross-sectional area of the abdominal oblique muscles is larger than that of the erector spinae group, as they wrap around the front and sides of the abdomen. If there is an imbalance in the forces between these four major muscle groups, the smaller erector spinae muscles have to compensate. Long-term compensation gradually weakens the fine motor control and flexibility functions of this muscle group, affecting the stability and mobility of the spine. Severe cases can lead to lateral spinal curvature and nerve compression, causing pain. Lateral curves below 10 degrees can often be corrected through training, while those above 40 degrees typically require surgical intervention, with various treatment options for intermediate cases.

Frequently observe and adjust your seated posture and weight distribution.

Each person has habitual seated postures and a tendency to favor one side. While sitting for work or daily activities, you may unconsciously shift your center of gravity to one side of your pelvis. Starting now, take a few seconds to observe your center of gravity when driving, in meetings, working, streaming, gaming, riding the subway, and during other daily activities, and consciously adjust it as needed. You can also seek guidance from professionals to correct any pelvic tilt.

When your center of gravity is balanced between your feet and sitting bones, you can experience a sense of physical comfort and integrate this into your everyday life. This not only helps prevent and alleviate low back pain but can also address any coldness in your lower limbs.