Backward walking exercise improvs lumbopelvic movement control in patients with chronic non-specific low back pain classified as lumbar flexion syndrome

Title
Backward walking exercise improves lumbopelvic movement control in patients with chronic non-specific low back pain classified as lumbar flexion syndrome

Author information
Ellen CHAN, [email protected]
Lok Yi CHAN, [email protected]
Hung Kit FONG, [email protected]
Yiu To MAK, [email protected]
Eliza Rui Sun, [email protected]
Sharon Man Ha TSANG, [email protected]
Affiliation: Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Kowloon, Hong Kong

Abstract
Background and purpose:
Low back pain is the most prevalent yet heterogenic musculoskeletal disorder globally. Non-specific low back pain (NSLBP) patients with lumbar flexion syndrome experience an increase in symptoms during lumbar flexion and tend to acquire a relatively flexed posture. Backward walking which promotes the preferential recruitment of lumbar extensors for reversing the flexed spinal posture has been advocated as a therapeutic intervention for this LBP subgroup. This prospective, cross-sectional, randomized clinical trial aims to examine the a) real-time changes of muscle activation during backward-walking, and b) the immediate effect after backward-walking exercise on movement control and muscle activation in chronic NSLBP patients classified as lumbar flexion syndrome.

Methods:
Thirty participants with chronic NSLBP with flexion syndrome received the assessments of their movement control during the five-minute forward walking test, before and immediately after a 15-minute treadmill walking training in either forward or backward direction, and real-time during the walking training. Primary outcome measures included pain intensity, normalized electromyography (EMG) of lumbopelvic muscles during walking, and performance of the lumbar movement control tests (LMC). Two-way repeated measures analysis of variance (ANOVA) was used to investigate the between- and within-subject effects differences for the a) immediate and b) real-time effects of the single session of walking training designated in forward versus backward direction.

Results:
Maximum tolerable gait speed was found to be a covariate for normalized EMG of lumbopelvic muscles. Gender was found to be a covariate for pain intensity and performance in LMC tests. To eliminate the confounding effect from covariates, two-way repeated measures analysis of covariance (ANCOVA) was adopted accordingly. Significant overall between-group effect (p=0.022-0.026) and time-and-group interaction effect (p=0.004-0.022) of ipsilateral internal oblique (IO) to multifidus (MF) ratio were found in swing phases of both legs, with real-time decreasing trend during backward walking training. For ipsilateral erector spinae (ES) to rectus abdominus (RA) ratio, significant time effect (p=0.022), between-group differences (p=0.031), and real-time reduction during forward walking in left swing phase, and significant between-group differences (p=0.024), time-and-group interaction effect (p=0.009), and real-time increase during backward walking in right swing phase were noted. Real-time increasing trend during backward walking and real time decreasing trend of ipsilateral MF to ES ratio during forward walking were observed in stance phase of both legs, with time-and-group interaction effect at sixth (p=0.007) and twelfth minute (p=0.006) during walking training in left stance phase. Significant real-time increase in co-contraction index (CCI) of ipsilateral IO and MF during backward walking in right swing phase was observed (p<0.0083). Significant post-training reduction in pain intensity (p=0.014) and improvement in overall performance of the LMC tests (p=0.006) was found after backward walking training.

Conclusions:
Backward walking exercise benefited LBP patients with lumbar flexion syndrome by inducing real-time enhancement in back extensors and stabilizing muscle recruitment and immediate post-training improvement in pain intensity as well as LMC test performance. Further research with longer treatment duration is recommended to better understand if greater and more sustainable therapeutic effect can be achieved with the walking exercise in backward direction for this specified LBP subgroup.

Keywords
Backward walking, lumbopelvic movement control, chronic non-specific low back pain, lumbar flexion syndrome

Funding acknowledgement
There was no funding received for this study.

Ethics approval
Ethical approval was obtained from the Institutional Review Board of The Hong Kong Polytechnic University (Reference no.: HSEARS20220928003).