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The following is a summary of “Understanding the flexion-relaxation phenomenon in non-specific chronic low back pain patients throught immersive virtual reality feedback approach,” published in the July 2024 issue of Rheumatology by Kevin et al.

The flexion-relaxation phenomenon (FRP) is missing in patients with non-specific chronic low back pain (NSCLBP).

Researchers conducted a retrospective study using immersive virtual reality (IVR) to explore if the absence of FRP in patients with NSCLBP is due to the pathology or limited trunk flexion.

They enrolled 15 patients with NSCLBP and 15 participants with no symptoms and similar characteristics. Using IVR combined with a motion capture system, avatars were created to mirror participants’ movements. Participants’ trunk kinematics and lumbar muscle electromyography were also measured. The IVR environment displayed a closed room with a mirror reflecting the avatar and a target line for trunk flexion. The avatars’ trunk movements were adjusted to exceed the participants’ maximum trunk flexion, encouraging controls to flex more than the normal voluntary limit.

The result showed that under IVR conditions, patients with NSCLBP significantly increased the trunk flexion angles, which led to a marked improvement in the FRP. The increase in trunk flexion under IVR conditions was not observed in the participants with no symptoms.

Investigators concluded that the lack of FRP in the population with NSCLBP was mainly due to limited trunk flexion.

Source: nature.com/articles/s41598-024-65983-5