Development of Test Protocols for Analysis of Low Back Exertions in Standing Position

Abstract

More than 80 percent of people suffer from low back pain at some point in their lifetime costing losses of up to $9 billion because of treatment and loss of work hours in the US alone. Kinematics and kinetics of body movements can be affected by low back pain and may result in spinal instability. The aim of this study was to develop testing procedure to quantify stability of the spine during low back motion using both traditional and non-linear methods in standing position. The objective was to quantify movements that are performed repetitively in flexion - extension (FE), lateral bending (LB), and rotation (ROT) of the trunk using traditional and non-linear methods. The study was approved by Institutional Review Boards (IRB) of Auburn University, AL as well as Palmer College of Chiropractic, IA. Nine healthy test subjects were recruited for the study using word of mouth and screened for eligibility by licensed clinicians. Participants were asked to perform 10 cycles of flexion - extension, lateral bending and rotation motion against no resistance, 5 lb, 10 lb and 15 lb resistance. Motion data was recorded at a frequency of 120 Hz for each exertion and for each resistance. Range of Motion (ROM) and non-linear techniques (Correlation Dimension (CoD), Approximate Entropy (ApEn)) were employed to analyze the motion data. EMG data was recorded at a frequency of 1200 Hz from six muscle groups: Erector Spinae, Multifidus, Latissimus Dorsi, Internal Obliques, External Obliques and Rectus Abdominis. Mean and median frequency of the recorded signals were analyzed to see the effect of increasing load on muscle fatigue. The ROM values varied from 7.5 – 40.2 Deg. For FE, 9.06 – 44.6 Deg. for LB and 6.68 – 21.3 Deg. for ROT, the ApEn values ranged from 0.133 – 0.40 while the CoD values ranged from 1.79 – 2.47. The overall results indicated that variability did not change significantly with increasing loads. The EMG results indicated that fatigue was not induced in participant’s muscles which might have helped them provide required neuromuscular response to increasing loads. However it is important to keep in mind that the main objective of the thesis was development of test protocol for analysis of low back motion. The test protocol developed herein needs to be further fine tuned before it can be applied for larger studies. Testing method for data recording during rotations needs improvement as there might be inaccuracy involved due to skin motion altering the position of sensors. Also, once the protocol is perfected, further testing needs to be carried out on a larger sample size so that the results can be generalized. Future studies need to consider the following recommendations for obtaining more meaningful data based on healthy subjects. 1) Increase the resistance to motion so that higher fatigue is induced in the participant. 2) Ask the participant to perform the exertions at two different fixed speeds. 3) To minimize the effect of skin stretching during rotation, a plastic plate can be attached to the skin before motion sensors are attached. Once the data base on healthy subjects is obtained, studies on low back pain subjects can be undertaken.