Individuals With and Without Low Back Pain Use Different Motor Control Strategies to Achieve Spinal Stiffness During...

Area of Science:

• Biomechanics
• Motor Control
• Orthopedics

Background:

• The prone instability test is a clinical tool to identify low back pain (LBP) patients who may benefit from trunk stabilization exercises.
• The underlying mechanism of pain reduction during this test, specifically muscle activation and spinal stiffness, requires further investigation.

Purpose of the Study:

• To compare changes in pain and spinal stiffness across different positions of the prone instability test.
• To analyze and contrast trunk and limb muscle activation patterns during the leg-raising component of the test in individuals with and without LBP.

Main Methods:

• A case-control laboratory study involving 10 participants with LBP and 10 without.
• Spinal stiffness was quantified using a beam-bending model and 3D kinematic analysis.
• Surface electromyography (sEMG) captured muscle activity, with principal-component analysis used to identify muscle synergies.

Main Results:

• Spinal stiffness increased significantly across test positions in all participants.
• Participants with LBP reported reduced pain during the test.
• No significant difference in spinal stiffness was observed between groups during leg raising.
• Individuals without LBP utilized 3 distinct muscle synergies, while those with LBP employed 2, indicating a simpler activation pattern.

Conclusions:

• While spinal stiffness increases in all individuals during the prone instability test, those with LBP demonstrate a less differentiated muscle synergy pattern.
• The observed global stabilization strategy in LBP participants may represent a maladaptive response to enhance spinal stability.