Abstract:
1. This article analyzes the relationship between side sleeping and lower back pain.
2. During side sleeping, the rotation of the torso is mainly achieved through the cooperation of the large muscles, including the four major muscles of the internal and external obliques, as well as the small muscles of the transverse processes.
3. Prolonged rotation to one side (including daytime movement patterns) gradually disrupts the balance of these four major muscles.
4. Imbalance in the major muscles forces the nearby small muscles to overwork in order to maintain stability.
5. Prolonged overuse of the small muscles leads to a loss of flexibility, resulting in misalignment of the lumbar spine.
6. Once the misalignment compresses the nerves, it can cause pain, numbness, and even incontinence.
7. It is recommended to consult professionals for testing and assistance in correcting the issue, or consider changing the sleeping position before bedtime.
Waking up with lower back pain, difficulty getting out of bed, and even immobility can often be attributed to side sleeping positions. It is possible that issues arising from daytime activities are magnified and become apparent during several hours of sleep.
For example, in golf, when the right-handed player swings, the spine rotates forcefully to the left. If the preferred sleeping position is still on the left side, the chances of experiencing lower back pain are higher than for the average person. If your workstation is located on the left side, which side should you choose to sleep on? The right side!
Taking the right side sleeping position as an example
when lying on the right side, the left leg is on top, causing internal rotation of the left hip and external rotation of the right hip joint. According to the principle of a pulley system, in this position, the pelvis rotates to the left, and the thoracic cavity rotates to the right. So, what is the state of the four major muscles of the internal and external obliques in this position? It’s important to understand whether these muscles are in a shortened or lengthened state.
Imbalance of the internal and external obliques during side sleeping (right side example):
- The left external oblique and the right internal oblique, as agonist muscles, are responsible for rotating the thoracic cavity to the right in this position, and they are in a shortened state.
- The left internal oblique and the right external oblique, as antagonist muscles, are lengthened in this position.
- Over time, this habitual imbalance strengthens the shortened muscles and weakens the lengthened muscles.
- This muscle recruitment pattern affects other postures and movements in daily life, where the strong muscles are recruited first, faster, and stronger.
Balanced state of the internal and external obliques on the same side:
| Spinal rotation | Left internal oblique abs | Left external oblique abs | Right internal oblique abs | Right exnternal oblique abs |
| Spinal left rotation | Concentric contraction ＋ | Antagonistic deceleration － | Concentric contraction ＋ | Antagonistic deceleration － |
| Spinal right rotation | Antagonistic deceleration － | Concentric contraction ＋ | Antagonistic deceleration － | Concentric contraction ＋ |
The fibers of the internal and external obliques on the same side have opposite directions and movements. The same applies to the left and right sides of the same layer. This forms an X-shaped structure (as shown in the diagram) with two opposing forces and mutual balancing. The forces along the diagonal direction are consistent. These four muscles play different roles: two are responsible for rotating the spine, and the other two act as antagonists to slow down the rotation (like brakes), making the spine both flexible and stable. For more details, refer to the attached explanation at the end of the article.
Compensation relationship between large and small muscles during spinal rotation:
The large superficial muscles of the body are mainly responsible for major movements and postures, while the deep, small muscle groups are responsible for fine adjustments during movements and postures. Once the superficial muscles become imbalanced, the deep, small muscles have to exert more effort to maintain balance. This is the compensation of the small muscles for the imbalances caused by the large muscles.
The major muscles involved in spinal rotation are the abdominal internal and external obliques (large muscles) and the small muscle group of the transverse processes in the back.
Excluding congenital diseases, our bodies are designed to be balanced and have clear divisions of labor. However, the combination of the sense of security in infancy and the habits of the caregiver, along with the habits developed during growth and professional activities, gradually forms a unique structural pattern. If the daytime movement pattern already involves rotation to the right, then sleeping on the right side at night exacerbates the compensation of the small transverse process muscles.
When the small muscles compensate for a prolonged period and become strained, their function weakens, and they lose the ability to finely adjust balance. As a result, joint imbalance occurs, leading to abnormalities in the lumbar spine. The degree and intensity of rotation vary, resulting in different diagnoses on magnetic resonance imaging reports, such as lumbar disc slippage or herniation (possibly anterior or posterior protrusion).
How to test whether the internal and external obliques are imbalanced:
Lie flat on your back with your legs straight and your arms at your sides.
1. Place your hands on your lower ribs, just above your hips, with your fingertips pointing towards your head.
2. Slowly roll onto your right side, keeping your legs straight and your feet stacked on top of each other.
3. Pay attention to the sensation in your abdominal muscles. Do you feel more tension or engagement on the right side compared to the left side?
4. Repeat the test on the left side and compare the sensations.
If you notice a significant difference in tension or engagement between the right and left sides, it may indicate an imbalance in the internal and external oblique muscles.
Correcting the issue:
If you suspect an imbalance in the internal and external oblique muscles or experience lower back pain during side sleeping, it is recommended to consult with a healthcare professional such as a physical therapist, chiropractor, or orthopedic specialist. They can provide a comprehensive evaluation and recommend specific exercises or treatments to address the imbalance and alleviate lower back pain.
Additionally, considering changing your sleeping position may also be beneficial. Experimenting with different sleep positions, such as sleeping on your back or using supportive pillows to align your spine during side sleeping, may help reduce strain on the lower back and promote better spinal alignment.
Conclusion:
The relationship between side sleeping and lower back pain lies in the imbalance created by prolonged rotation to one side. This imbalance affects the major muscles responsible for spinal rotation, leading to compensation by the small muscles, which can result in misalignment of the lumbar spine and subsequent lower back pain. Seeking professional assistance and considering changes in sleeping position may help address this issue and alleviate lower back pain associated with side sleeping.
Post time: May-11-2024