Thoracolumbar fascia mobility and chronic low back pain: Phase 1 of a pilot and feasibility study assessing repeated measures and the influence of paraspinal muscle contraction.

BACKGROUND

Differential movement, or shear strain (SS), between layers of thoracolumbar fascia is reduced with chronic low back pain. To provide a foundation for clinical research involving SS, this study assessed temporal stability and the effect of paraspinal muscle contraction on SS in persons with chronic low back pain.

METHODS

We used ultrasound imaging to measure SS in adults self-reporting low back pain ≥1 year. Images were obtained by placing a transducer 2-3 cm lateral to L2-3 with participants lying prone and relaxed on a table moving the lower extremities downward 15°, for 5 cycles at 0.5 Hz. To assess paraspinal muscle contraction effects, participants raised the head slightly from the table. SS was calculated using 2 computational methods. Method 1 averaged the maximum SS from each side during the third cycle. Method 2 used the maximum SS from any cycle (2-4) on each side, prior to averaging. SS was also assessed after a 4-week no manual therapy period.

RESULTS

Of 30 participants (n = 14 female), mean age was 40 years; mean BMI 30.1. Mean (SE) SS in females with paraspinal muscle contraction was 66% (7.4) (method 1) and 78% (7.8) (method 2); 54% (6.9) (method 1) and 67% (7.3) (method 2) in males. With muscles relaxed, mean SS in females was 77% (7.6) (method 1) or 87% (6.8) (method 2); 63% (7.1) (method 1) and 78% (6.4) (method 2) in males. Mean SS decreased 8-13% in females and 7-13% in males after 4-weeks

CONCLUSION

Mean SS in females was higher than males at each timepoint. Paraspinal muscle contraction temporarily reduced SS. Over a 4-week no-treatment period, mean SS (with paraspinal muscles relaxed) decreased. Methods less likely to induce muscle guarding and enabling assessment with broader populations are needed.