Objective To investigate associations between deep abdominal muscle activation and long-term pain outcome in chronic non-specific low back pain (LBP).
Methods Recruitment of transversus abdominis and obliquus internus abdominis during the abdominal drawing-in manoeuvre was recorded by B-mode ultrasound and anticipatory onset of deep abdominal muscle activity with M-mode ultrasound. Recordings were done before and after 8 weeks with guided exercises for 109 patients with chronic non-specific LBP. Pain was assessed with a numeric rating scale (0–10) before and 1 year after intervention. Associations between muscle activation and long-term pain were examined by multiple linear and logistic regression methods.
Results Participants with a combination of low baseline lateral slide in transversus abdominis and increased slide after intervention had better odds for long-term clinically important pain reduction (≥2 points on the numeric rating scale) compared with participants with small baseline slide and no improvement in slide (OR 14.70, 95% CI 2.41 to 89.56). There were no associations between contraction thickness ratios in transversus abdominis or obliquus internus abdominis and pain at 1-year follow-up. Transversus abdominis lateral slide before intervention was marginally associated with a lower OR for clinically important improvement in pain at 1-year follow-up (OR 0.76, 95% CI 0.62 to 0.93). Delayed onset of the abdominal muscles after the intervention period was weakly associated with higher long-term pain.
Conclusion Improved transversus abdominis lateral slide among participants with low baseline slide was associated with clinically important long-term pain reduction. High baseline slide and delayed onset of abdominal muscles after the intervention period were weakly associated with higher pain at 1-year follow-up.
Clinical Trial Registration number The study was preregistered in ClinicalTrials.gov with identifier NCT00201513.
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Funding The trial was funded by the Norwegian fund for postgraduate training in physiotherapy.
Competing interests None.
Patient consent Obtained.
Ethics approval The study was approved by the regional ethics committee.
Provenance and peer review Not commissioned; externally peer reviewed.