LUMBAR SPINE MOBILIZATION: MEASUREMENT AND EFFECTS

Abstract

Low Back Pain (LBP) is the second most common cause of disability in the United States, and it is associated with abnormal high activity of Erector Spinae (ES) and low activity of Lumbar Multifidus (LM) muscles. This abnormal activity of muscles has shown to be associated with pain and dysfunction in people with LBP. Lumbar mobilization is a common physical therapy intervention for LBP. Yet, there is a lack of knowledge about the effects of lumbar mobilization on the activity of back muscles in both healthy subjects and in people with LBP. Investigating such effect of mobilization on the activity of back muscles may lead to a better understanding of the physiological effects of mobilization, and a better application of mobilization to normalize the abnormal activity of back muscles in LBP. This may improve the intervention outcomes and decrease the disability in people with LBP. Furthermore, there is a need to measure lumbar mobilization in clinical settings due to the inconsistency in applying mobilization, which may affect the intervention outcomes. Current laboratory methods like Optotrak and force plate to measure mobilization are expensive and not portable. Inertial Measurement Unit (IMU) is a potential device to measure the clinician’s hand movement during mobilization. IMU is inexpensive and portable. However, the validity and reliability of IMU in measuring mobilization need to be determined before its application is considered in clinical and research settings. In chapters two and three, the effect of mobilization on the activity/contraction of back muscle was investigated. Ultrasound imaging and surface electromyogram (EMG) were used to measure LM contraction and activity of ES respectively at low isometric contraction (arm lift task). In chapter two, the effect of lumbar mobilization on both LM and ES muscles in healthy subjects was investigated. Healthy subjects received three intervention sessions (no intervention, placebo, and grade IV mobilization) on different days. Contraction of LM and the EMG amplitude of ES activity were measured at two time points (before and immediately after the intervention) in each session. The only significant effect of lumbar mobilization was found on LM contraction compared to the placebo effect (the mobilization increased the LM contraction), whereas there was no significant effect of mobilization on LM contraction compared to no intervention. In chapter three, the effect of lumbar mobilization on both LM and ES muscles in people with LBP was investigated. LBP subjects were randomly assigned into two groups (grade III mobilization or placebo/light touch group). Subjects received intervention based on their assigned group and for two sessions. Contraction of LM, the activity amplitude and the activity onset of ES were measured at two time points (before and immediately after the intervention) in each session. Compared to the placebo group, there were significant effects of lumbar mobilization on the activity amplitude and the activity onset of ES, and on LM contraction. The mobilization decreased both activity amplitude and activity onset of ES, and increased the contraction of LM. The findings support the use of lumbar mobilization to decrease the activation impairment of back muscles and decrease the disability in people with LBP In chapter four, the validity and reliability of IMU in measuring clinician’s hand displacement during mobilization were investigated. Healthy subjects received four different amplitudes of lumbar mobilization by two clinicians in two sessions. The validity of IMU was tested by comparing the IMU measurements (displacement) to the measurements of Optotrak (displacement), and calculating the correlation between IMU measurements (displacement) and the force plate measurement (force). The reliability of IMU was tested by comparing the IMU measurements between two clinicians (inter-rater reliability) and between two sessions (intra-rater reliability). Our results showed that IMU had high agreement with Optotrak and high correlation with force plate. Therefore, IMU was found to be a valid device to measure the amplitude of displacement of clinicians’ hand during lumbar mobilization. The reliability of IMU was moderate (both inter-reliability and intra-reliability), which can be due to inconsistency in applying mobilization between sessions and between clinicians. The findings suggest that lumbar mobilization may change the activity/contraction of back muscle in people with LBP but not in healthy subjects during the arm lift task used to collect outcomes. That might be because healthy subjects do not have an impairment in activity/ contraction of back muscle to be corrected by mobilization. Therefore, the findings further support the use of mobilization as an integral intervention for people with LBP, and emphasize a new therapeutic effect of lumbar mobilization to normalize back muscle impairment in LBP. Though IMU was found as a valid device to measure lumbar mobilization, the reliability of IMU needs to be tested with more accurate methods of replicating the mobilization between sessions and between clinicians.