Association between lumbopelvic motion and muscle activation in patients with non-specific low back pain during forward bending task: A cross-sectional study.

Background: Evidence suggests patients with non-specific low back pain (NSLBP) have altered lumbar and pelvic movement patterns. These changes could be associated with altered patterns of muscle activation.

Objective: The study aimed to determine: (1) differences in the relative contributions and velocity of lumbar and pelvic movements between people with and without NSLBP, (2) the differences in lumbopelvic muscle activation patterns between people with and without NSLBP, and (3) the association between lumbar and pelvic movements and lumbopelvic muscle activation patterns.

Methods: Subjects (8 healthy individuals and 8 patients with NSLBP) performed 2 sets of 3 repetitions of active forward bending, while motion and muscle activity data were collected simultaneously. Data derived were lumbar and pelvic ranges of motion and velocity, and ipsilateral and contralateral lumbopelvic muscle activities (internal oblique/transverse abdominis (IO/TA), lumbar multifidus (LM), erector spinae (ES) and gluteus maximus (GM) muscles).

Results: Lumbar and pelvic motions showed trends, but exceeded 95% confidence minimal detectable difference $($ MDD ${}_{95})$ , for greater pelvic motion $(p=0.06)$ , less lumbar motion $(p=0.23)$ among patients with NSLBP. Significantly less activity was observed in the GM muscles bilaterally $(p<0.05)$ in the NSLBP group. A significant association $(r=-0.8$ , $p=0.02)$ was found between ipsilateral ES muscle activity and lumbar motion, while moderate, but statistically non-significant associations, were found between GM muscle activity bilaterally and lumbar velocity $($ ipsilateral: $r=-0.6$ , $p=0.14$ ; contralateral: $r=-0.6$ , $p=0.16)$ in the NSLBP group.

Conclusion: Findings indicated patients had greater pelvic contribution, but less lumbar contribution which was associated with less activation of the GM bilaterally.