Matching Items (7)
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- All Subjects: Biomechanics
- Creators: Abbas, James
Description
Gait and balance disorders are the second leading cause of falls in the elderly. Investigating the changes in static and dynamic balance due to aging may provide a better understanding of the effects of aging on postural control system. Static and dynamic balance were evaluated in a total of 21 young (21-35 years) and 22 elderly (50-75 years) healthy subjects while they performed three different tasks: quiet standing, dynamic weight shifts, and over ground walking. During the quiet standing task, the subjects stood with their eyes open and eyes closed. When performing dynamic weight shifts task, subjects shifted their Center of Pressure (CoP) from the center target to outward targets and vice versa while following real-time feedback of their CoP. For over ground walking tasks, subjects performed Timed Up and Go test, tandem walking, and regular walking at their self-selected speed. Various quantitative balance and gait measures were obtained to evaluate the above respective balance and walking tasks. Total excursion, sway area, and mean frequency of CoP during quiet standing were found to be the most reliable and showed significant increase with age and absence of visual input. During dynamic shifts, elderly subjects exhibited higher initiation time, initiation path length, movement time, movement path length, and inaccuracy indicating deterioration in performance. Furthermore, the elderly walked with a shorter stride length, increased stride variability, with a greater turn and turn-to-sit duration. Significant correlations were also observed between measures derived from the different balance and gait tasks. Thus, it can be concluded that aging deteriorates the postural control system affecting static and dynamic balance and some of the alterations in CoP and gait measures may be considered as protective mechanisms to prevent loss of balance.
ContributorsBalasubramanian, Shruthi (Author) / Krishnamurthi, Narayanan (Thesis advisor) / Abbas, James (Thesis advisor) / Buneo, Christopher (Committee member) / Arizona State University (Publisher)
Created2014
Description
Spinal cord injury (SCI) disrupts the communication between supraspinal circuits and spinal circuits distal to the injury. This disruption causes changes in the motor abilities of the affected individual, but it can also be used as an opportunity to study motor control in the absence or limited presence of control from the brain. In the case of incomplete paraplegia, locomotion is impaired and often results in increased incidence of foot drag and decreased postural stability after injury. The overall goal of this work is to understand how changes in kinematics of movement and neural control of muscles effect locomotor coordination following SCI. Toward this end, we examined musculoskeletal parameters and kinematics of gait in rats with and without incomplete SCI (iSCI) and used an empirically developed computational model to test related hypotheses. The first study tested the hypothesis that iSCI causes a decrease in locomotor and joint angle movement complexity. A rat model was used to measure musculoskeletal properties and gait kinematics following mild iSCI. The data indicated joint-specific changes in kinematics in the absence of measurable muscle atrophy, particularly at the ankle as a result of the injury. Kinematic changes manifested as a decrease in complexity of ankle motion as indicated by measures of permutation entropy. In the second study, a new 2-dimensional computational model of the rat ankle combining forward and inverse dynamics was developed using the previously collected data. This model was used to test the hypothesis that altered coordination of flexor and extensor muscles (specifically alteration in burst shape and timing) acting at the ankle joint could be responsible for increases in incidence of foot drag following injury. Simulation results suggest a time course for changes in neural control following injury that begins with foot drag and decreased delay between antagonistic muscle activations. Following this, beneficial adaptations in muscle activation profile and ankle kinematics counteract the decreased delay to allow foot swing. In both studies, small changes in neural control caused large changes in behavior, particularly at the ankle. Future work will further examine the role of neural control of hindlimb in rat locomotion following iSCI.
ContributorsHillen, Brian (Author) / Jung, Ranu (Thesis advisor) / Abbas, James (Committee member) / Muthuswamy, Jit (Committee member) / Jindrich, Devin (Committee member) / Yamaguchi, Gary (Committee member) / Arizona State University (Publisher)
Created2012
Description
Olecranon fractures account for approximately 10% of upper extremity fractures and 95% of them require surgical fixation. Most of the clinical, retrospective and biomechanical studies have supported plate fixation over other surgical fixation techniques since plates have demonstrated low incidence of reoperation, high fixation stability and resumption of activities of daily living (ADL) earlier. Thus far, biomechanical studies have been helpful in evaluating and comparing different plate fixation constructs based on fracture stability. However, they have not provided information that can be used to design rehabilitation protocols such as information that relates load at the hand with tendon tension or load at the interface between the plate and the bone. The set-ups used in biomechanical studies have included simple mechanical testing machines that either measured construct stiffness by cyclic loading the specimens or construct strength by performing ramp load until failure. Some biomechanical studies attempted to simulate tendon tension but the in-vivo tension applied to the tendon remains unknown. In this study, a novel procedure to test the olecranon fracture fixation using modern olecranon plates was developed to improve the biomechanical understanding of failures and to help determine the weights that can be safely lifted and the range of motion (ROM) that should be performed during rehabilitation procedures.
Design objectives were defined based on surgeon's feedback and analysis of unmet needs in the area of biomechanical testing. Four pilot cadaveric specimens were prepared to run on an upper extremity feedback controller and the set-up was validated based on the design objectives. Cadaveric specimen preparation included a series of steps such as dissection, suturing and potting that were standardized and improved iteratively after pilot testing. Additionally, a fracture and plating protocol was developed and fixture lengths were standardized based on anthropometric data. Results from the early pilot studies indicated shortcomings in the design, which was then iteratively refined for the subsequent studies. The final pilot study demonstrated that all of the design objectives were met. This system is planned for use in future studies that will assess olecranon fracture fixation and that will investigate the safety of rehabilitation protocols.
Design objectives were defined based on surgeon's feedback and analysis of unmet needs in the area of biomechanical testing. Four pilot cadaveric specimens were prepared to run on an upper extremity feedback controller and the set-up was validated based on the design objectives. Cadaveric specimen preparation included a series of steps such as dissection, suturing and potting that were standardized and improved iteratively after pilot testing. Additionally, a fracture and plating protocol was developed and fixture lengths were standardized based on anthropometric data. Results from the early pilot studies indicated shortcomings in the design, which was then iteratively refined for the subsequent studies. The final pilot study demonstrated that all of the design objectives were met. This system is planned for use in future studies that will assess olecranon fracture fixation and that will investigate the safety of rehabilitation protocols.
ContributorsJain, Saaransh (Author) / Abbas, James (Thesis advisor) / LaBelle, Jeffrey (Thesis advisor) / Jacofsky, Marc (Committee member) / Arizona State University (Publisher)
Created2015
Description
Injuries and death associated with fall incidences pose a significant burden to society, both in terms of human suffering and economic losses. The main aim of this dissertation is to study approaches that can reduce the risk of falls. One major subset of falls is falls due to neurodegenerative disorders such as Parkinson’s disease (PD). Freezing of gait (FOG) is a major cause of falls in this population. Therefore, a new FOG detection method using wavelet transform technique employing optimal sampling window size, update time, and sensor placements for identification of FOG events is created and validated in this dissertation. Another approach to reduce the risk of falls in PD patients is to correctly diagnose PD motor subtypes. PD can be further divided into two subtypes based on clinical features: tremor dominant (TD), and postural instability and gait difficulty (PIGD). PIGD subtype can place PD patients at a higher risk for falls compared to TD patients and, they have worse postural control in comparison to TD patients. Accordingly, correctly diagnosing subtypes can help caregivers to initiate early amenable interventions to reduce the risk of falls in PIGD patients. As such, a method using the standing center-of-pressure time series data has been developed to identify PD motor subtypes in this dissertation. Finally, an intervention method to improve dynamic stability was tested and validated. Unexpected perturbation-based training (PBT) is an intervention method which has shown promising results in regard to improving balance and reducing falls. Although PBT has shown promising results, the efficacy of such interventions is not well understood and evaluated. In other words, there is paucity of data revealing the effects of PBT on improving dynamic stability of walking and flexible gait adaptability. Therefore, the effects
of three types of perturbation methods on improving dynamics stability was assessed. Treadmill delivered translational perturbations training improved dynamic stability, and adaptability of locomotor system in resisting perturbations while walking.
of three types of perturbation methods on improving dynamics stability was assessed. Treadmill delivered translational perturbations training improved dynamic stability, and adaptability of locomotor system in resisting perturbations while walking.
ContributorsRezvanian, Saba (Author) / Lockhart, Thurmon (Thesis advisor) / Buneo, Christopher (Committee member) / Lieberman, Abraham (Committee member) / Abbas, James (Committee member) / Deep, Aman (Committee member) / Arizona State University (Publisher)
Created2019
Description
Nearly one percent of the population over 65 years of age is living with Parkinson’s disease (PD) and this population worldwide is projected to be approximately nine million by 2030. PD is a progressive neurological disease characterized by both motor and cognitive impairments. One of the most serious challenges for an individual as the disease progresses is the increasing severity of gait and posture impairments since they result in debilitating conditions such as freezing of gait, increased likelihood of falls, and poor quality of life. Although dopaminergic therapy and deep brain stimulation are generally effective, they often fail to improve gait and posture deficits. Several recent studies have employed real-time feedback (RTF) of gait parameters to improve walking patterns in PD. In earlier work, results from the investigation of the effects of RTF of step length and back angle during treadmill walking demonstrated that people with PD could follow the feedback and utilize it to modulate movements favorably in a manner that transferred, at least acutely, to overground walking. In this work, recent advances in wearable technologies were leveraged to develop a wearable real-time feedback (WRTF) system that can monitor and evaluate movements and provide feedback during daily activities that involve overground walking. Specifically, this work addressed the challenges of obtaining accurate gait and posture measures from wearable sensors in real-time and providing auditory feedback on the calculated real-time measures for rehabilitation. An algorithm was developed to calculate gait and posture variables from wearable sensor measurements, which were then validated against gold-standard measurements. The WRTF system calculates these measures and provides auditory feedback in real-time. The WRTF system was evaluated as a potential rehabilitation tool for use by people with mild to moderate PD. Results from the study indicated that the system can accurately measure step length and back angle, and that subjects could respond to real-time auditory feedback in a manner that improved their step length and uprightness. These improvements were exhibited while using the system that provided feedback and were sustained in subsequent trials immediately thereafter in which subjects walked without receiving feedback from the system.
ContributorsMuthukrishnan, Niveditha (Author) / Abbas, James (Thesis advisor) / Krishnamurthi, Narayanan (Thesis advisor) / Shill, Holly A (Committee member) / Honeycutt, Claire (Committee member) / Turaga, Pavan (Committee member) / Ingalls, Todd (Committee member) / Arizona State University (Publisher)
Created2022
Description
Introduction. Intervertebral disc degeneration (DD) is one of the most common diagnoses in patients with neck pain and contributes to worldwide disability. Despite the advances in diagnostic imaging today, little is known about functional status of cervical DD. The purpose of this research was to 1) develop and validate an ovine model of cervical spine DD, 2) to quantify and compare the effect of disc lesions on dynamic spinal stiffness, and 3) study the effect of disc lesions on spinal accelerations and displacements during two types of spinal manipulative therapy (SMT). Methods. Fifteen sheep received surgically induced disc injury to the mid-cervical spine via scalpel wound a minimum of five months earlier and 15 sheep served as controls. All animals were biomechanically assessed at the level of the lesion using swept-sine mechanical loads from 0-20 Hz under load control to quantify dynamic dorsoventral (DV) spine stiffness (load/deformation, N/mm). The effect of disc lesion on stiffness was assessed using a one-factor repeated measures ANOVA comparing 32 mechanical excitation frequencies. Tri-axial accelerometers rigidly attached to adjacent vertebrae across the target level further evaluated the effect of disc lesion on spinal motion response during two types of SMTs. A 2x6x2 repeated measures ANOVA examined the effect of disc lesion and SMT force-time profile on spine motion response. Postmortem histological analysis graded specimens at the target site and comparison was made with descriptive statistics. Results. Annular disc tears were only observed in the disc lesion group and the mild degeneration identified was localized to the injured annular tissue that did not progress to affect other areas of the disc. No difference in overall DD grading was found among the groups. DV stiffness was significantly increased in the disc lesion group by approximately 34% at 31 of 32 frequencies examined (p<.05). SMTs resulted in decreased displacements in the disc lesion group (p<.05), and SMT type significantly influenced spinal accelerations for both the DV and axial planes. Conclusion. Disc lesions in the ovine cervical spine produce localized annular degenerative changes that increase the cervical spine dynamic stiffness and reduce its spinal motion response during manual examination and treatment that is further augmented by the force-time profile administered by the clinician.
ContributorsColloca, Christopher (Author) / Hinrichs, Richard N (Thesis advisor) / Abbas, James (Committee member) / Ringenbach, Shannon (Committee member) / Hooker, Steven (Committee member) / Arizona State University (Publisher)
Created2015
Description
This dissertation aimed to evaluate the effectiveness and drawbacks of promising fall prevention strategies in individuals with stroke by rigorously analyzing the biomechanics of laboratory falls and compensatory movements required to prevent a fall. Ankle-foot-orthoses (AFOs) and functional electrical stimulators (FESs) are commonly prescribed to treat foot drop. Despite well-established positive impacts of AFOs and FES devices on balance and gait, AFO and FES users fall at a high rate. In chapter 2 (as a preliminary study), solely mechanical impacts of a semi-rigid AFO on the compensatory stepping response of young healthy individuals following trip-like treadmill perturbations were evaluated. It was found that a semi-rigid AFO on the stepping leg diminished the propulsive impulse of the compensatory step which led to decreased trunk movement control, shorter step length, and reduced center of mass (COM) stability. These results highlight the critical role of plantarflexors in generating an effective compensatory stepping response. In chapter 3, the underlying biomechanical mechanisms leading to high fall risk in long-term AFO and FES users with chronic stroke were studied. It was found that AFO and FES users fall more than Non-users because they have a more impaired lower limb that is not fully addressed by AFO/FES, therefore leading to a more impaired compensatory stepping response characterized by increased inability to generate a compensatory step with paretic leg and decreased trunk movement control. An ideal future AFO that provides dorsiflexion assistance during the swing phase and plantarflexion assistance during the push-off phase of gait is suggested to enhance the compensatory stepping response and reduce more falls. In chapter 4, the effects of a single-session trip-specific training on the compensatory stepping response of individuals with stroke were evaluated. Trunk movement control was improved after a single session of training suggesting that this type of training is a viable option to enhance compensatory stepping response and reduce falls in individuals with stroke. Finally, a future powered AFO with plantarflexion assistance complemented by a trip-specific training program is suggested to enhance the compensatory stepping response and decrease falls in individuals with stroke.
ContributorsNevisipour, Masood (Author) / Honeycutt, Claire (Thesis advisor) / Sugar, Thomas (Thesis advisor) / Artemiadis, Panagiotis (Committee member) / Abbas, James (Committee member) / Lee, Hyunglae (Committee member) / Arizona State University (Publisher)
Created2019