Reliability and validity of standing back extension test for detecting motor control impairment in subjects with low back pain

Introduction: Low back pain is a chronic health problem with high socioeconomic impact. Specific diagnosis or treatment approach has not yet effectively established to treat chronic low back pain. Standing Back Extension Test is one of the clinical measures to detect the passive extension subgroup of Motor Control Impairment (MCI); which could have an impact on spinal stability leading to recurrent chronic low back pain. Reliability and validity of this test is not fully established.Aim: To determine the intra-rater and inter-rater reliability and concurrent validity of the Standing Back Extension Test for detecting MCI of the lumbar spine.Materials and Methods: A total of 50 subjects were included in the study, 25 patients with Non Specific Low Back Pain (NSLBP) (12 men, 13 women) and 25 healthy controls (12 men,13 women) were recruited into the study. All subjects performed the test movement. Two raters blinded to the subjects rated the test performance as either ‘Positive’ or ‘Negative’ based on the predetermined rating protocol. The thickness of Transverse Abdominis (TrA) muscle was assessed using Rehabilitative Ultrasound Imaging (RUSI).Statistical test used: For reliability, the kappa coefficient with percent agreement was calculated and for assessing the validity Receiver Operator Characteristic (ROC) curves and Area under the Curve (AUC) were constructed.Results: The standing back extension test showed very good intra-rater (k=0.87 with an agreement of 96%) and good inter- rater (k=0.78 with an agreement of 94%) reliability and high AUC for TrA muscle.Conclusion: The standing back extension test was found to be a reliable and a valid measure to detect passive extension subgroup for MCI in subjects with low back pain.