Background: Comminuted supracondylar femur fractures in the elderly are often treated with either retrograde femoral nailing or locked plating. Early weight-bearing is typically restricted after fixing supracondylar fractures, thereby impairing the patient's mobilization. In general, surgeons are more comfortable allowing early weight-bearing of long bone fractures after nailing rather than plating, but early studies of retrograde nails for supracondylar fractures using standard distal locking showed poor fixation compared with locked plating. Newer generation distal locking techniques, such as the spiral blade, may demonstrate improved fixation, potentially allowing early weight bearing. The purpose of this study is to biomechanically compare locked plating with retrograde nailing of osteoporotic supracondylar femur fractures with simulated physiologic weight-bearing in the post-operative period. Methods: The Locking Condylar Plate (LCP) and Retrograde/Antegrade EX Femoral Nail (RAFN) with spiral blade locking were tested using 10 paired elderly cadaveric femurs, divided into normal and low BMD groups, with a simulated AO/OTA type 33-A3 supracondylar femur fracture. Each specimen was subjected to 200,000 loading cycles simulating six weeks of postoperative recovery with full weight-bearing for an average individual and the construct subsidence and axial stiffness were measured. Results: LCP fixation compared to RAFN showed higher axial stiffness for normal and low BMD groups (80% and 57% respectively). After cyclic loading, axial stiffness of both constructs decreased by 20% and RAFN fixation resulted in twice as much subsidence (1.9±0.6 mm). Two RAFN constructs with low BMD failed after a few cycles whereas the matched pairs fixed with LCP failed after 68,000 and 100,000 cycles. Conclusions: The LCP construct was stiffer than RAFN construct. Early weight bearing may cause 3-4 mm of subsidence in elderly patients with low BMD. However, because of the observed failures in two of the samples treated with RAFN in the low BMD group, early weight bearing is not recommended in osteoporotic bones treated with RAFN. / Mechanical Engineering

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Maintaining effective performance under stress can be challenging, especially in the dangerous environments encountered by the police and military personnel. This document reviews the impact of stress on performance, discusses breath interventions as a means of stress mitigation, suggests an approach for exploring the value of a breath intervention in police cadets, tests, analyzes, and discusses a test of this method and results. Biofeedback training can be used to produce resonance breathing that is synchronized with heart rate and optimizes heart rate variability (HRV). This intervention was expected to alleviate physiological and subjective stress responses. Studies reviewed confirm that higher HRV is associated with lower stress and better cognitive performance. Training resonance breathing produces similar results when studies are well-designed. Relative to controls, resonance breathing training should improve the performance of police cadets on a series of cognitive and physical tests included in their curriculum, and on a simulated operational scenario given at the end of training. Research also tested whether personality traits associated with resilience predict higher baseline HRV and better performance during training.

Obesity is the primary risk factor for the development and progression of medial compartment knee osteoarthritis. Laterally-wedged insoles reduce many of the biomechanical risk factors for disease development and progression in osteoarthritis patients and lean individuals but it is unknown how efficacious they may be for asymptomatic, but at-risk, obese women. 14 Obese and 14 Control women participated. The purpose of the first study was to examine how an 8° laterally-wedged insole affected the kinetics and kinematics of the lower extremity. The results of a gait analysis indicated that the insole reduced the peak external knee adduction moment and the impulse of the moment in both groups while minimally affecting the kinematics of surrounding joints. A second study examined the benefits of the wedge on the mediolateral shift in the center of pressure on the tibial plateau. A musculoskeletal modeling analysis estimated muscle forces and joint contact forces. The results showed that the wedge laterally shifted the center of pressure of the joint contact force and redistributed a portion of the mechanical load off the medial compartment of the knee joint. This partial unloading of the medial compartment has critical implications for medial knee osteoarthritis prevention. The final study quantified the coordination patterns between articulating segments of the lower extremity. The purpose of this study was to determine if the insole detrimentally affected the coupled rotations. The results of a vector coding analysis indicated similar coupled transverse rotations of the leg and thigh segments and of the transverse rotations of the leg and frontal plane rotations of the foot. In conclusion, the insole may be used to relieve a biomechanical problem at the knee joint without detrimentally affecting the coordinated rotations of the lower extremity segments. The results of these studies suggest that biomechanical benefits may be achieved through the use of laterally-wedged insoles in obese populations. Thus, obese individuals who are at risk for medial compartment knee osteoarthritis may be able to use the wedged insole to delay or prevent disease onset.

The arms and thorax are integral parts of the human body for locomotion. However, the legs have been the focus of study in a majority of research on human walking and running. The human body functions best when all the parts work together as a cohesive unit. The overall aim of these studies was to analyze changes in arm, thorax and pelvis interactions under various manipulations, and to relate those findings to angular momentum control. Manipulations used were: gait speed, arm and thorax kinematics (removal of arm swing and reduction of axial rotation), age and mode of locomotion (walking and running). In the first study, manipulating arm swing and axial rotation led to changes in thorax-pelvis coordination and upper and lower body angular momentum that were designed to maintain angular momentum control through adapted arm swing. Walking without arm swing resulted in an increase in the range of whole-body angular momentum. This increase in angular momentum could potentially lead to problems in maintaining balance. In the second study, older adults demonstrated a smaller change than young adults did in thorax-pelvis coordination with increasing speed. However angular momentum differences were apparent at slower speeds but not faster, indicating that older adults regulate angular momentum independently of coordination, and do so differently than young adults. In the third study, walking and running locomotion modes led to a different organization of thorax-pelvis coordination and arm swing. This resulted in an inverse relationship between coordination and angular momentum regulation. The more out-of-phase coordination pattern in walking had smaller arm swing, while a more in-phase coordination pattern in running was associated with greater arm swing. In both modes of locomotion, arm swing was used to generate angular momentum to counter that of the legs. The general finding from these studies is that angular momentum is a factor of human locomotion that is regulated regardless of the degree of thorax-pelvis coordination in order to allow the momentum of the arms to counter that of the legs. This balance of angular momentum is likely important for the energetics and control of walking, and is an indirect result of the linking of upper and lower body movements. Arm swing is important for regulating angular momentum and plays a key role in countering the momentum generated by the legs.

Obesity is a well-defined mechanical factor for osteoarthritis (OA). More than one-third of adults in the United States are obese, and one in three obese adults has arthritis. In obese individuals, knee pain is highly prevalent and is often thought to be the first symptom of knee OA. In the pathomechanics of knee OA, altered kinematics and contact location in the knee joint are potent contributors to OA initiation and progression. However, such kinematics and cartilage contact location in obese individuals, and how the knee joint responses to excess load due to obesity are not clear and understudied, mainly limited by the instrumentations. Therefore, we conducted a series of dissertation studies to investigate the effect of weight on the knee joint kinematics in six degrees of freedom (6DOF) and cartilage contact location using a fluoroscopic imaging system with magnetic resonance-based morphological models. In Study 1, the 6DOF kinematic analysis showed that obese individuals with knee pain walked with a reduced range of flexion-extension motion and a reduced medial-lateral translation compared with non-obese controls. In Study 2, the cartilage contact analysis showed that obese individuals experienced different contact location on both the tibial and femoral cartilage surfaces during walking when compared with a healthy group, while pain had a minimal effect on the cartilage contact location. In Study 3, we followed up with the obese individuals in Study 1 and the kinematic analysis showed that the change in range of the flexion-extension and adduction-abduction motion during gait were associated with the change in body weight; however, knee pain was not associated with the kinematic change. In conclusion, this series of dissertation studies suggests that the kinematics of the knee in obese individuals with knee pain was modifiable through weight loss. Weight management should be addressed more than controlling for pain in obese individuals with pain, as pain management might not able to restore the contact locations. / 2020-07-06T00:00:00Z

BACKGROUND: Knee osteoarthritis is a debilitating disease largely affecting the elderly population, impacting their quality of life through joint pain and decreased mobility. Shock attenuation at the knee has been one measure associated with increased pain due to the inability to properly absorb shock as one performs physical activities such as walking and running. Although there is currently no cure to knee osteoarthritis, there are many treatments ranging from exercise to surgical interventions that aim to minimize these negative symptoms and prevent further joint degradation and disease severity. RESEARCH QUESTION/PURPOSE: This thesis aims to examine shock attenuation at the knee during walking and its association with muscle activation and disease severity in people with knee osteoarthritis. In addition, this study will investigate the effects of exercise intervention on shock attenuation at the knee in this population of individuals. METHODS: 295 individuals with confirmed knee osteoarthritis were recruited from surrounding communities in this study. Of these 295 participants, 58 participants were included in a 12-week follow-up study to compare the effects of exercise therapy. All muscle activation and shock attenuation data were collected using a 13-camera motion capture system and muscle co-contraction was measured using electromyography (EMG) sensors. A multivariate regression model accounting for age, sex, and BMI was sued to analyze the association between shock attenuation at the knee and disease severity as well as with muscle activation. A linear mixed model was also used to the difference between repeated measures in analyzing the effects of exercise intervention on shock attenuation. RESULTS: Shock attenuation from shank to thigh and as calculated by coupled vector angle had a significant negative correlation with disease severity characterized by an increase in Kellgren-Lawrence grade as well as a positive correlation with Knee Injury and Osteoarthritis Outcome (KOOS) pain scores. An increase in vastus lateralis and left hamstring muscle co-contraction was also associated with a decrease in coupled vector angle. In analyzing the effects of exercise intervention on shock absorption, there was a significant decrease in shock attenuation from the shank to thigh after a 12-week follow-up study. DISCUSSION: As the knee osteoarthritis disease severity progresses, patients will also experience lower shock attenuation and increased pain. In addition, increased muscular co-contraction between the vastus lateralis and left hamstring corresponded with a decrease in coupled vector angle. Our results also suggest that exercise may decrease a patient’s ability to absorb shock at the knee. / 2026-03-15T00:00:00Z

Stroke survivors define the recovery of safe, efficient, and independent walking as a top research priority after stroke. Eighty percent of stroke survivors experience significant and lasting walking challenges with approximately 1/4 of survivors unable to achieve independent walking by three months after stroke. The heterogeneous nature of post stroke recovery presents a significant challenge in developing more targeted, personalized walking interventions after stroke. The effectiveness of neurorehabilitation to facilitate motor recovery is predicated on the ability of the nervous system to reorganize and remodel (i.e., neuroplasticity) in response to an intervention. Aerobic exercise generates neuroplastic potential meaningful for motor learning; this is largely evidenced by improvements in motor skill acquisition, accuracy, and retention in neurologically-intact individuals following an acute bout of high intensity exercise. The beneficial priming effect of high intensity aerobic exercise suggested by these results is exciting, especially in the context of stroke motor recovery, yet the exact mechanisms contributing to the beneficial priming effect of exercise on learning are not well defined. In contrast, it is well-recognized that, along with task-specificity and amount of practice, aerobic intensity is a critical training parameter for walking recovery interventions after stroke. Indeed, higher aerobic training intensities have generally contributed to greater improvements in walking function, as measured by improvements in functional measures of walking speed and endurance, in addition to cardiovascular fitness. Given the evidence, recent clinical practice guidelines for stroke gait rehabilitation emphasize training intensity to not only drive cardiovascular benefits but to also promote neuroplastic changes that maximize the potential for motor learning after stroke. That is, beyond the amount of practice, the intensity of practice is considered a critical component of the “dose” of training. However, strategies to optimize the dosage of training parameters for a given stroke survivor remain largely undefined. Taken together, there is a recognized need to (i) expand the evidence-base of performance measures that may aid in optimizing training dose, including the (ii) use of biomarkers, and to (iii) explore promising interventions focused on optimizing the intensity of practice. Study 1 of this dissertation is meant to expand the evidence-base of performance measures that may aid in optimizing training dose by improving the ability to monitor training intensity—a critical component of training dose—during walking after stroke. To that end, I developed and validated five equations that can be used by clinicians at point-of-care to more accurately and reliably measure training intensity compared to the current standard proxy measure, heart rate monitoring. Study 2 of this dissertation is meant to evaluate the effects of a novel soft robotic exosuit-assisted walking intervention focused on optimizing training intensity, as well as the value of an intensity-dependent molecule, brain-derived neurotrophic factor (BDNF), as a biomarker of treatment efficacy. Results suggest that exosuit-assistance may promote high intensity walking training, at a level that elicits an increase in serum BDNF levels, and in a manner that may reduce the reliance on propulsion-based compensatory walking mechanics that worsen peak propulsion symmetry. / 2024-01-17T00:00:00Z

BACKGROUND: Lumbar spinal stenosis (LSS) in older adults is a leading cause of pain and limitations to mobility. Compression of the spinal nerves can result in neurological symptoms that can decrease walking capacity and overall quality of life. It is clinically believed that patients with LSS alter their gait pattern to be able to increase their walking capacity but biomechanical assessment of spinal and pelvic motion during walking compared to healthy older adults is lacking. The purpose of this study was to gain further insight into how patients with LSS move and how their posture affects spinal loading compared to healthy older adults. METHODS: Whole body motion data was collected on 9 patients with LSS and 10 healthy older adults. Both cohorts completed a 3D opto-electronic motion analysis during standing and walking trials and patients with LSS were measured during both asymptomatic and symptomatic states. Pelvis, knee, and spine kinematics and spinal loading were obtained via subject-specific musculoskeletal models. RESULTS: In the LSS group, both asymptomatic and symptomatic trials, the average pelvic tilt was more posteriorly rotated than the healthy adults during standing and walking. Lumbar spine angles in the LSS group adopted a more flexed posture compared to the healthy group’s normal lordotic angle. This coincided with higher C7/S2 angles and distances compared to the healthy group. Lumbar spine loading doubled in both LSS groups compared to the healthy group’s standing trials, though little difference was seen during walking. Knee flexion angle increased greatly during both standing and walking. CONCLUSIONS: My results indicate that LSS patients both stand and walk with greater posterior pelvic tilt and lumbar flexion which greater knee flexion to counterbalance compared to healthy counterparts. While the provocation of symptoms did not affect their kinematics, both asymptomatic and symptomatic states showed significant modification from older healthy adults. The clear differences in gait and posture can aid in therapeutic interventions but additional work is needed to better understand the biomechanical differences between these two groups.

Blood pressure waveform (BPW) can be used to characterize changes in the cardiovascular system due to diseases and aging. The BPW morphology is largely determined by both the total mechanical impedance of the vasculature and the flow waveform produced by the left ventricle. The BPW can be further decomposed into its two primary components: the forward and reflected waveforms. It is known that under several conditions, such as aging, arterial wall stiffening, and increased cardiovascular risk, the magnitudes and phases of these waves change and therefore distort the aggregate BPW. Previous studies of the BPW has yielded mixed results, largely due to the insensitivities of the primary wave morphology index, augmentation index (AI). To this end, a new method of morphology characterization was developed which takes into account the overall harmonic content of the BPW. Harmonic distortion (HD), derived from Fourier-transformed BPW, was first used to characterize changes in the aortic wall. Utilizing mice subjected to normal and high fat, high-sucrose diets, the results demonstrate that HD exhibits a linear relationship with both systolic blood pressure (SBP) and arterial stiffness. Next, a transmission line model of arterial impedance was developed to study physiologically realistic BPWs under various arterial tree sizes and stiffness. Comparison of HD and other indexes reveals that HD correlates strongly with arterial stiffness, surpassing AI in accuracy for higher stiffness values. Finally, HD analysis was applied to BPWs collected clinically on a diverse group of participants. HD emerges as a more sensitive indicator than AI, notably correlating with diabetes and demonstrating stability across heart rate variations. The superior statistical performance of HD over AI in hemodynamic variables underscores its potential as a robust measure for cardiovascular risk assessment. This research offers a comprehensive framework for assessing arterial health, highlighting the potential of HD as a stable, sensitive, and noninvasive measure. This integrated approach contributes to a nuanced understanding of the intricate factors influencing BPW morphology and its implications for cardiovascular health in the context of aging and disease.