Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 424-439). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Oregon, 2002. / Includes bibliographical references (leaves 178-188). Also available online.

To understand how falls occur during walking in older adults, we need to understand how the nervous system maintains stability, and how aging affects walking. Four studies were conducted to better understand the effect of age on gait. Older adults display higher gait variability compared to young adults, possibly because of their slower walking. We compared gait stability at multiple controlled walking speeds. Greater gait variability in healthy elderly existed independent of slower walking. Their diminished strength and flexibility partly explained this difference. To explain slower walking in the elderly, some have suggested that muscle weakness and stiffness may force people to walk slower. Others have suggested that people choose to walk slower to be more stable. We compared dynamic stability of gait at multiple speeds. Healthy older adults also exhibited more stability at slower speeds, yet walked at speeds comparable to young adults despite the lower strength and flexibility. Therefore, weakness and stiffness may not force healthy older adults to walk slower. The goal of the nervous system during walking may be to maintain stability of superior segments. We tested whether superior segments are more stable than inferior segments during walking. Superior segments exhibited less orbital stability during preferred walking speed, in contrast to previous suggestions. This highlighted the importance of trunk control during gait. The effects of aging on the fluctuations in the muscle activity during gait are not well understood. We quantified the stride-to-stride fluctuations of EMG as a measure of muscle activation patterns in state-space. Variability increased with speed except in the gastrocnemius. Orbital stability was less in older adults, suggesting that deviations in the EMG amplitude pattern were not readily corrected. Less local stability was seen in older adults, suggesting that older adults were more sensitive to perturbations. Together, these findings suggest that trunk control is important during gait. Strength and flexibility deficits help explain higher variability and lower stability in older adults. Future work will need to address the effect of strength interventions, neurophysiological decline on gait stability and fall risk.

Recorded on July 27, 2007 by Eugene Barsky, Physiotherapy Outreach Librarian, UBC / N/A

Objective: gait of patients after stroke. Stroke is acute vascular disturbance in the brain, which involves sensory and motor systems of the opposite side to the brain lesion. Inability to walk or abnormal gait pattern is one of the biggest problem after cerebral vascular accident, which predispose the stoke survivors to a sedentary lifestyle, which further limits the individual’s activities of daily living and reduces cardiovascular reserves. One of the primary goals for physical therapy is to restore the ability to walk. It is the first step in becoming independent. In this case the main purposes of this study – to evaluate the influence of the physical therapy of gait of stoke patients. The tasks to reach the purpose of this study were: 1) to assess the effectiveness of special active walking exercises in order to regain the gait; 2) to assess the effectiveness of balance exercises in order to regain the gait; 3) to compare the effectiveness of different physiotherapy methods. The study was performed in physical medicine and rehabilitation department of Virsuziglis rehabilitation hospital. Thirty patients after cerebral vascular stoke, took part in this study. They were divided in two groups. The first group’s patients besides the traditional physical therapy performed special active walking exercises. The second group’s patients additionally were applied balance exercises. These used research methods: “Up and Go” test, Berg balance scale, motor assessment scale, Smidt... [to full text]

Knee osteoarthritis (OA) is a progressive disease and a leading cause of morbidity in older adults, resulting in severe mobility limitations. While the osteoligamentous and neuromuscular systems are altered in knee OA, little data is available to illustrate an association among these systems. The objective of this dissertation was to improve our understanding of how muscle activation patterns during gait are altered across the knee OA severity spectrum and to examine how factors related to the OA process are associated with these alterations. Three independent but related studies were conducted. Muscle activation of the medial and lateral orientations of the gastrocnemii, quadriceps and hamstrings were recorded during gait using surface electromyography for all three studies. Key activation features were identified using principal component analysis. First, participants selected from a large group (n=272) of individuals classified as asymptomatic, ii) moderate ii) severe knee OA were matched for walking velocity. Significant amplitude and temporal activation characteristics were found, supporting that differences among OA severities exist and were not the result of walking velocity only. Secondly, individuals with moderate OA were sub-grouped based on structural severity determined using Kellgren-Lawrence radiographic scores (II-IV) and were compared to a velocity-matched asymptomatic group. Medial gastrocnemius, lateral hamstring and quadriceps amplitudes and temporal patterns were significantly altered by structural severity where significant activation imbalances between the lateral:medial gastrocnemii and hamstrings were found with greater structural impairment (score>II). Thirdly, individuals with moderate OA were prospectively evaluated and divided into knee effusion and no effusion groups, based on a positive bulge test. A significantly higher knee flexion angle during mid-stance, higher quadriceps amplitudes and prolonged hamstrings amplitudes were found when effusion was found. These studies showed that muscle activation patterns during walking were related to i) OA presence and severity based on functional, symptoms and radiographic evidence, ii) structural severity and iii) knee joint effusion. These findings improve our understanding of the interrelationships between alterations in joint structure and function associated with knee OA and muscle activation patterns during gait. These data can contribute to the development of gait-based metrics that can facilitate knee OA diagnosis and monitor progression.

Knee osteoarthritis is a debilitating disease causing pain and disability in adults. Biomechanical factors including obesity, abnormal magnitude and load distribution have been cited to play a role in its initiation and progression with its definite cause being multi-factorial. Total knee arthroplasty has become the treatment of choice for knee osteoarthritis and although the procedure is mostly successful, there are some patients who experience implant failures which necessitates revision surgery. Revision surgery is more complicated and thus there is the need to monitor patients who have undergone TKA so as ensure better outcomes and also address problems much earlier. Objective methods like Radiostereometric Analysis (RSA) has proven to be a good tool at diagnosing these implant failures. Inducible displacement with RSA has the potential to serve as a one-time measure to diagnose implant failures. Previous studies have applied loads to induce motion to the knee in various ways- squatting, exercising and weight-bearing on the affected limb. This was not standardized and caused wide variations in the data. This work looked at refining a device used to apply standardized loads to the knee resulting in a more portable and faster way of applying load to the joint. Gait analysis is used to assess implant function pre and post surgery. Some gait patterns have also been related to implant failure. Previous works have focussed primarily on associations between well-working implants (non-revised patients) and these gait patterns (adduction moments and flexion angles). This work focussed on any differences in the gait patterns between patients who did not undergo revision surgery and those that did. Although most parameter differences did not reach statistical differences, they point to important trends that may explain the causative factors (adduction moments) whiles others may point to the effects of disease progression (external rotation).

The overall objective of this thesis was to compare compensatory reactions in young and older adults following unexpected platform perturbations in the frontal and sagittal planes during gait. Eleven young (aged 18-30) and ten community-dwelling older adults (aged 65+) completed a general health questionnaire, Mini BESTest, hip strength tests, and 45 walking trials on a motion platform. The walking trials were completed in a randomized block design on a 5 m pathway that moved following right heel contact after at least two steps. Young adults had stronger hips and performed better on the Mini BESTest than older adults. Compensatory reactions (measured through gait parameters and centre of mass motion) indicated that lateral perturbations were more difficult for both groups. These measures showed that young adults were able to recover more quickly than older adults. This could be attributed to altered base of support changes that occurred immediately following platform motions. / Ontario Graduate Scholarship

The progression of knee osteoarthritis (OA), the most common cause of physical disability in older adults, is influenced by muscular and biomechanical factors. Reliability of muscular and biomechanical measures, including knee muscle strength and limb alignment, is critical. Furthermore, conservative interventions that slow the course of OA disease progression and prevent disability are urgently needed. The objectives of this thesis were to: 1) investigate the reliability of measures of knee muscle strength and alignment in persons with knee OA, and 2) determine the influence of an exercise intervention targeting hip muscles on knee joint loading in those with medial knee OA. In the first study reliability of knee muscle strength measures was evaluated within one testing session in 40 persons with knee OA. Isometric and isokinetic peak torque values for the quadriceps and hamstring muscles demonstrated high degrees of intra-session reliability. Reliability of lower limb alignment measures was determined following a bone landmark-based approach with use of a computer program. Excellent reliability coefficients were found which compared favorably with reliability of manual measures from schematics of limb deformities drawn with AutoCAD® software. When the computer method was applied to 100 full-limb radiographs of persons with or at risk for knee OA, alignment measures demonstrated high inter- and intra-reader reliability. Hip muscle weakness may influence loading of the medial knee compartment. Hip abductor strength was evaluated in 40 individuals with medial compartment knee OA in comparison to a control group of 40 healthy older adults. The effect of an 8-week home-based hip abductor strengthening program on the knee adduction moment was also assessed in this group with knee OA, compared with the control group which received no intervention. Following the exercise program the OA group demonstrated improvements in hip abductor strength and functional performance on a sit-to-stand task. There were no changes in the knee adduction moment. Thus, hip muscle strengthening did not influence joint loading, but may improve function in persons with knee OA. Results from this thesis provide increased understanding of knee OA, from muscular and biomechanical perspectives, in the areas of measurement reliability and exercise intervention. / Thesis (Ph.D, Rehabilitation Science) -- Queen's University, 2008-09-25 01:29:13.675

Spinal adaptive response in the frontal plane was investigated in relationship to pelvic unleveling during gait. Kinematic data were collected from 10 healthy adult subjects (5 male, 5 female) for walking and running on the treadmill at self-selected speeds. Spine and pelvic kinematic patterns and ranges of motion (ROM) were investigated with gender, speed and slope as factors. Speed and slope had the greatest impact on changes in the amplitude of the spine's kinematic patterns. Interaction effects were seen for speed and slope for the ROM, particularly of the greater trochanter (p < .047), PSIS (p < .011) and for the shoulders (p < 0.077). Gender presented more changes in the pelvic kinematics than the spine's kinematics. A significant trend in the females of greater ROM for T8 with increases in speed and slope was shown (p < 0.001). From this study it was concluded that speed, slope and gender were significant factors that affect the spine's ability to adapt to pelvic unleveling. In all conditions there was a coupled relationship found between the thoracic spine, lumbar spine and pelvis. In particular there was an oppositional movement found within the spine such that as the lumbar spine had convexity towards the swing leg then the thoracic spine had the opposite convexity. Hence, these factors are important when assessing posture and biomechanics of running and walking.