The effect of pelvic compression on deep abdominal muscle thickness during the active straight leg raise test

Abstract

Background/Aims: The estimated prevalence of sacroiliac joint (SIJ) pain is 13–30% in patients with non-specific low back pain. One common presentation is pain at or near the SIJ, and common physical therapy interventions include lumbopelvic stabilisation programmes and pelvic compression belts. The aim of this study was to: i) assess how compression of the SIJ affects the thickness of the deep abdominal muscles during the active straight leg raise (ASLR); ii) determine between-day intra-tester reliability of ultrasound imaging to assess percentage change in thickness of the deep abdominal muscles. Methods: Participants (n=15) with unilateral symptoms near the SIJ and age-matched and sex-matched controls (n=15) were recruited for this study. Ultrasound imaging was used to obtain the thickness of the transverse abdominis (TrA) and internal oblique (IO) muscles. Measurements were taken at rest and during the ASLR, with and without pelvic compression. Results: Two separate two-way (group × pelvic compression) analysis of variance (ANOVA) designs with repeated measures were used to analyse the thickness of the TrA and IO muscles; interactions were not significant for percentage change in the TrA (p=0.57) or IO (p=0.10) muscles. Intra-tester reliability was higher when testing with pelvic compression and in the control group (ICC: 0.85–0.89 vs 0.70–0.76). Conclusions: Pelvic compression did not immediately affect the muscular response of the TrA or IO muscles during the ASLR. Pelvic compression belts may be used to address the passive systems of the pelvis by increasing stability; however, specific localised exercises may be needed to improve the percentage change in thickness of the deep abdominal muscles during the ASLR.