Award Date

May 2023

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Interdisciplinary Programs

First Committee Member

Szu-Ping Lee

Second Committee Member

Kai-Yu Ho

Third Committee Member

Richard Tandy

Fourth Committee Member

Jaclyn Sions

Fifth Committee Member

Hans Rawhouser

Number of Pages



Many people with lower extremity amputation (LEA) experience lower back pain (LBP). The amount of pain they experienced can be debilitating and severely interferes with activities of daily living. Previous studies have explored LBP in populations without LEA, and the evidence is also growing within the limb loss population. However, the mechanism for the high prevalence of LBP after LEA remains unclear. The lower back muscles, specifically the multifidi muscles, play an important role in stabilization of the spine during motion, and LBP has been associated with decreased mobility in patient populations, but the degree of dysfunction in the spinal muscles related to the presence of LBP has not been quantified in individuals with LEA. Therefore, in this dissertation, we first developed and tested the reliability of a clinical-based test that may help clinicians to see where mobility deficits may be present in the LEA population with and without LBP (Chapter 2), thus potentially guiding treatment plans to incorporate targeted training. We also assessed the multifidi muscle activity to determine if there are differences in activity levels between those who have LBP and those who do not have LBP during a functional task.One of the characteristics of a muscle that is associated with strength and stability is its thickness. Generally, the thicker the muscle, the stronger it is. Understanding the thickness and activity of these multifidus muscles during submaximal contractions is key to understand the morphology of the paraspinal muscle in response to LBP. One readily available tool to assess muscle thickness is musculoskeletal ultrasound imaging (USI). USI has not been widely used to examine this population, specifically those with LEA and LBP. Therefore, in Chapter 3, we first sought to establish reliability of USI in this population. We then used USI to measure the thickness of the multifidus muscles in those with LEA and LBP and those without LBP, both at rest and during submaximal contractions, to compare between groups to see if there are differences in the thicknesses of the muscles associated with the presence of LBP. Two key aspects of muscle performance are strength and fatigability, especially in muscles that are designed for stability like the multifidi muscles. Thus, in Chapter 4, we tested spinal extensor strength and endurance using standardized clinical tests. We then examined the multifidi activity level during the endurance test as a percentage of their maximal activation. In this study, we examined whether those who reported LBP experienced fatigue earlier than those who do not have pain. We also compared muscle activation between the groups. Overall, our findings suggest that there may be differences in the multifidi muscles between those with LEA and LBP and those with LEA and no LBP. The two tests (i.e., reaching tests and USI measurement for muscle thickness) we implemented in this population were shown to be reliable. Furthermore, our results showed that individuals with LEA and LBP exhibited significant deficits in reaching and muscle endurance performance. We believe these data are valuable as benchmarks for continuing to build the evidence in this area.


amputee; endurance; Low back pain; reaching; strength; ultrasound


Physical Therapy | Physiotherapy

Degree Grantor

University of Nevada, Las Vegas




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