Does Muscular Flexion–relaxation Response Change Due to Static Flexion?

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A study 1 in the journal of Clinical Biomechanics shared results pointing toward the relationship between the muscular flexion-relaxation response in humans and period of static flexion. The aim was to further understand the phenomenon and its link to muscular modification (including low back pain).

Understanding Static Lumbar Flexion

Research has shown that workers are at risk of static lumbar flexion. However, not a lot of data is present that experimentally addresses the physiological biochemical and histological processes that are active in the evolutionary progression of the resulting low back disorder. Studies, involving animals, have shared that static lumbar flexion is responsible for the development of creep in associated viscoelastic tissues. This leads to elicit spasms and even modifies muscle function.

The current study set out to investigate neuromuscular changes while assessing normal (health-wise) human participates through the flexion-relaxation phenomenon.

The Study

The current research included male and female participants. There were 24 males and 25 female participants. The males ranged from 22 to 40 in age (the mean being 23.7 years old). The females were 19 to 30 in age (with the mean being 23.3 years). None of the participants reported issues in their spinal functions. Take note, six additional participants served as a control group.

They were asked to perform three bouts of lumbar flexion-extension before as well as after a 10 minutes long period of static flexion. The researchers recorded the surface electromyographic from the erector spinae muscles along with the flexion angle.

ANOVA was utilized on the angle in which electromyographic was reduced during flexion and initiated during the extension stage.

The Results

The study saw that the human erector spinae were active through a significantly larger angle during the flexion stage and were able to initiate activity significantly earlier during the extension stage (after static flexion). More pronounced changes were seen in the female participants (compared to the male participants). Furthermore, spasms were recorded by the researchers in more than 50% of the participants during the static flexion period.

What does it all mean?

According to the study, it was concluded that creep which was developed during a short static lumbar flexion was able to elicit a significant change in the flexion-relaxation phenomenon’s muscular activity pattern (in humans). It was observed that due to the loss of tension in the lumbar viscoelastic tissues, the muscles offered some compensation. The recorded spasms suggested minor micro-damage due to the viscoelastic tissues. The data was helpful in understanding why static lumbar flexion was an activity that was a risk factor for the development of the low back disorder in humans.

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