Stabiliser Muscle Disuse as a Result of Poor Posture

Several mechanisms have been proposed as contributing factors to the relationship between low back pain and posture, including a possible spinal overload arising from changes in vertebral orientation and motor control, as well as decreased muscle activity that leads to muscle atrophy due to disuse and deconditioning.

 

Guo et al (2014) has looked at paravertebral muscle (such as multifidus, erector spinae and psoas muscle) changes in patients with degenerative lumbar instability by MRI to observe and assess the degeneration of paravertebral muscles. The study was also interested in the analysis of the relationship between paravertebral muscle degeneration and lumbar curvature.

 

The cross-sectional area (CSA) and percentage of fat infiltration area (FIA) of the paravertebral muscles at the L4-S1 levels were measured using MRI, and lumbar curvature (expressed as lumbar lordosis angle) was measured in lumbar X-ray.

 

The difference of multifidus cross-sectional area and the percentage of fat infiltration in the patients of degenerative lumbar instability at the L4-L5, L5-S1 level, compared with the control group, was statistically significant. The percentage of fatty infiltration in erector spinae also showed significant differences. It was noted that the lumbar lordosis angle in patients with degenerative lumbar instability was higher than in the control group.

 

Pezolato et al (2012) states that individuals with sway-back posture have an identified decreased lumbar stabiliser muscle activity. Muscle disuse, as consequence of the posture adopted, can lead to atrophy, which is characterised by a reduced cross-sectional area and by fat infiltration.

 

Increased intramuscular fat deposits affect the contractility of the muscles with stabilising functions and makes individuals prone to segmental instability. The effect of decreased contractility of these muscles required for control of spinal orientation and intervertebral motion may result in pain and disability. The minimum amount of fat required to predict the onset of pain and functional limitations is not yet known.

 

Pezolato et al study results indicate that “individuals with sway-back posture may be susceptible to morphological changes in their lumbar erector spinae and lumbar multifidus muscles, both due to the presence of pain and as a consequence of their habitual posture.”

 

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Ref: Guo X, Zhang X, Ding W, Yang D, Ma L, Xie D, Wang H, Wang H, Lu K, Yang S. [Imaging study of paravertebral muscle degeneration in degenerative lumbar instability]. Zhonghua Wai Ke Za Zhi. 2014 Aug;52(8):571-5
Adriano Pezolato, Everaldo Encide de Vasconcelos, Helton Luiz Aparecido Defino, Marcello Henrique Nogueira-Barbosa. Fat infiltration in the lumbar multifidus and erector spinae muscles in subjects with sway-back posture. Eur Spine J (2012) 21:2158–2164

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