|dc.description.abstract||The pathology of low back pain (LBP) is often unclear, despite the fact that it is the most common musculoskeletal disorder (MSD) with hundreds of thousands of workers afflicted. One underlying mechanism that may contribute to LBP is muscular imbalance (MI) among the lumbar paraspinal and core muscles. It has been hypothesized that MI contributes to LBP, and that MI may be more pronounced in subjects that present with LBP than those without. It follows that, if MI can be reduced, LBP may subsequently be mitigated. It is possible that certain exercise regimens may reduce imbalance and therefore LBP related to such imbalances. The purpose of this doctoral work was to examine this relationship between MI and LBP. Specifically, this work sought to establish a novel method of quantifying MI, assess the linear relationship between MI and LBP, investigate physiological changes in trunk musculature and its relationship with MI-related LBP over time, and evaluate the effects of various forms of MI on MSDs using an epidemiological database of workers while controlling for psychosocial factors.
Magnetic Resonance Imaging (MRI) was used to collect scans of the low back and core muscles in subjects to precisely measure cross-sectional areas (CSAs) and mechanical lever arm lengths (MLALs). These scans were then used to quantify the degree to which muscles were imbalanced. Data regarding pain and exercise were collected via weekly subject survey on exercise intensity and duration, and LBP ratings. A cross-sectional analysis of the data examined MRI-derived lumbar paraspinal and core muscle CSAs from female subjects was conducted to assess the correlation between MI and LBP. A prospective analysis was used to evaluate how MI and LBP may change over time. A cross-sectional analysis was conducted to validate the proof of concept of physical imbalance and its impact on MSDs using an epidemiological ergonomic database consisting of health data on several measures of imbalance and their associations with LBP and the likelihood of LBP related medical attention sought.
A new measure of MI was established (MInew) and compared to previously accepted measures of MI (MICSA). MInew incorporates MLALs in combination with CSAs to correct for the individual mechanical advantages of paraspinal and core muscles to provide a more inclusive measure of MI than CSA difference alone. Linear regression found that exercise was not significantly related to LBP development and symptoms. Linear regressions determined that the L3/L4 spinal level was more associated with LBP than other levels. Tai Chi exercise was found to have some protective effect for MI and LBP. Different definitions of MI were investigated to test the underlying hypothesis that MI is causally related to pain. Significant odds ratios were found with respect to LBP and imbalance in an occupational setting, Age was shown to be strongly associated with imbalance.
This work is important in that it investigated novel models for measuring core muscle imbalances to provide input for evidence-based practice (EBP) guidelines. Establishing a model for measuring MI may help improve biomechanical models by introducing a new type of personal characteristic that may impact MSD risk, and subsequent pain. Exercises designed to stabilize and strengthen the core muscles have been shown to not only strengthen the paraspinal muscles but may also reduce LBP. This work adds to the growing body of literature suggesting the clinical benefits of incorporating low impact exercise in daily life to prevent/treat LBP. Meaningful results such as these provide evidence to conduct larger, more inclusive research studies on MI related LBP, and potential MI exercise interventions to prevent or alleviate LBP symptoms.||en_US