1 Department of Health, Kinesiology & Applied Physiology, Concordia University, Montreal, Canada.
2 Western Sydney University, Richmond, Australia.
3 Department of Health, Kinesiology & Applied Physiology, Concordia University, Montreal, Canada. maryse.fortin@concordia.ca.
4 School of Health, Concordia University, Montreal, Canada. maryse.fortin@concordia.ca.

Purpose: The purpose of this study was to investigate the relationship between different characteristics of the Thoracolumbar Fascia (TLF) (e.g., length, epimuscular fat distribution) with pain status and lumbar extension strength in a sample of participants with and without chronic low back pain (CLBP).

Methodology: This cross-sectional study included 27 individuals with CLBP (10 males, 17 females; mean age 41.45 ± 11.21 year) and 25 healthy controls (12 males, 13 females; mean age 36.56 ± 11.43 year). The length of the posterior (pTLF), middle (mTLF), and anterior (aTLF) TLF layers, the TLF circumference, and the distribution of epimuscular fat around the paraspinal muscles were assessed at L4 and L5 using MRI. Pain severity was collected using a visual analogue scale (VAS), and lumbar extension strength was measured using the MedX lumbar extension machine. ANCOVA testing and multiple regression models were used to assess possible differences in TLF characteristics between participants with and without CLBP, and partial correlations were used to assess the relationship between TLF characteristics and extension strength.

Results: We found no significant differences in TLF morphological characteristics between participants with and without CLBP. None of the TLF characteristics or epimuscular fat characteristics investigated were correlated with pain severity. Participants with CLBP showed no correlation between pTLF length and strength (r_avg = 0.276, r_max = 0.421, p > 0.05) contrary to healthy controls (r_avg = 0.527, r_max = 0.554, p < 0.05). The TLF circumference (r_maxL4 = 0.495 r_maxL5 = 0.571, p < 0.05) and fat surface of contact (r_avgL4 = 0.709, r_maxL4 = 0.596, p < 0.05) in CLBP participants were significantly correlated with back extension strength, contrary to healthy controls.

Conclusion: Future studies investigating TLF characteristics at multiple spinal levels while also considering the multidirectional and multilayered implications of the TLF are needed to better clarify the role of TLF morphology in spine biomechanics.