An investigation into the effects of manual technique targeted towards psoas major muscle on lumbar range of motion

Abstract

Background and objective: The relationship between the psoas muscle and lumbar range of motion has been little investigated. Limited literature exists that has investigated its role in lumbar range of movement. The aim of this study was to determine changes in lumbar range of motion following an osteopathic treatment of the psoas muscle versus a sham intervention.

Design: Randomized, assessor blinded, placebo controlled trial.

Methods: Twenty-five subjects (16 males, 9 females; mean age=38.3yrs, SD=10.8) met the inclusion/exclusion criteria and were enrolled in the study. Subjects were screened for clinical evidence of slight-to-moderate psoas dysfunction (low-to-moderate back pain, groin pain, or limitation in hip extension). Subjects were randomly assigned to receive either a psoas treatment intervention or a sham intervention. The primary outcome measure was change in lumbar range of motion (in flexion, extension, right- and left-side-bending) using the double-inclinometer method.

Results: There was little change post-intervention in lumbar flexion, extension, right- and left-side-bending. The effect size for post-intervention measures was ‘trivial to small’ (d=0.06 to 0.35) for the treatment group in all movements, and trivial to small (d=0.08 to 0.35) for the sham group. The percentage of subjects with changes less than the smallest detectable difference (SDD) was less than 10% for the treatment group, and approximately eight to 15% for the sham group in all ranges. The percentage of subjects with changes greater than the SDD was less than 10% for the treatment group, and less than 8% for the sham group in all ranges. Due to the difference noted between pre-conditioning and pre-intervention measures, a secondary analysis was undertaken based on a revised pre-intervention measure made up of an average of pre-conditioning means and pre-intervention means. The percentage of subjects measuring less than, within, or greater than the SDD were comparable to original measures. The effect size for these post-intervention measures for the treatment group was ‘trivial to small’ (d = 0.14 to 0.36), and for the sham group was ‘trivial to medium’ (d=0.06 to 0.53).

Conclusions: The results indicate that treatment of the psoas, as performed in this study, does not influence lumbar range of motion in flexion, extension, and right- and left-side-bending in subjects with mild dysfunction of the psoas muscle.