Darbo tikslas: įvertinti jauno amžiaus, fiziškai aktyvių asmenų, patyrusių kelio sąnario priekinių kryžminių raiščių plyšimą apatinių galūnių funkcinius rodiklius. Uždaviniai: 1) įvertinti vyrų ir moterų apatinių galūnių funkcijos rodiklius po PKR rekonstrukcijos uždaroje kinetinėje grandyje atliekant horizontalius šuolių testus; 2) Nustatyti vyrų ir moterų po PKR rekonstrukcijos judesio stereotipo ypatybes uždaroje kinetinėje grandyje atliekant vertikalius šuolių testus; 3) įvertinti vyrų ir moterų dinaminės pusiausvyros rodiklius po PKR rekonstrukcijos; 4) palyginti vyrų ir moterų operuotos kojos funkcijos rodiklius su sveikosios kojos rodikliais po PKR rekonstrukcijos. Tiriamieji ir metodika: tyrime ištirti 38 jauno amžiaus asmenys iš kurių 30 – vyrai (28,77 ± 7,9 metai) ir 8 moterys (26,50 ± 7,1 metai). Tiriamieji buvo padalinti į dvi grupes: 30 vyrų bei 8 moterys ir atliktas vienkartinis testavimas (tiriamiesiems buvo vertinama tiek operuota, tiek sveika koja). Siekiant įvertinti jauno amžiaus fiziškai aktyvių asmenų kelio sąnario funkcinę būklę buvo naudojami šie funkciniai testai: nužengimo nuo pakylos ir maksimalaus šuolio testas, dinaminio stabilumo “Y” testas bei šuolių viena koja testas. Tyrimo rezultatai ir išvados: 1. Įvertinus vyrų, patyrusių priekinių kryžminių raiščių traumą funkcinę apatinių galūnių būklę šuolių viena koja testais nustatyta, jog operuotosios kojos rodikliai buvo mažesni nei sveikosios tik trijų maksimalių šuolių viena koja testo metu. Moterų... [toliau žr. visą tekstą] / Aim: to assess the lower limbs’ function indexes of young active people, who suffered a tear of anterior cruciate ligament. Objectives: 1) to assess the lower limbs’ function indexes of females and males after the ACL reconstruction in a close kinetic chain with horizontal hop tests; 2) to identify peculiarities of movement stereotype of females and males after the ACL reconstruction in a close kinetic chain with vertical hop tests; 3) to assess the dynamic balance indexes of females and males after the ACL reconstruction; 4) to compare indexes of the leg after the ACL reconstruction surgery of females and males with ones of a healthy leg. Respondents and methodology: 38 young people, inc. 30 males (28,77 ± 7,9 y. o. ) and 8 females (26,50 ± 7,1 y. o. ). The respondents were divided into two groups: 30 males and 8 females and have underwent a single test (for a leg after surgery and a healthy one). In order to assess the lower limbs’ function indexes of young active people, the following tests have been used: drop vertical jump test, dynamic stability “Y” test and single leg hop test. Results and conclusions: 1. After assessment of the lower limbs’ function of males, who suffered a tear of anterior cruciate ligament with single leg hop tests, it has been identified that indexes of a leg after surgery were lower, compared to a healthy one only during the test of three maximum single leg hop test. Functional indexes of lower limbs for females were the same. 2. According to the... [to full text]

abstract: Fall accident is a significant problem associated with our society both in terms of economic losses and human suffering [1]. In 2016, more than 800,000 people were hospitalized and over 33,000 deaths resulted from falling. Health costs associated with falling in 2016 yielded at 33% of total medical expenses in the US- mounting to approximately $31 billion per year. As such, it is imperative to find intervention strategies to mitigate deaths and injuries associated with fall accidents. In order for this goal to be realized, it is necessary to understand the mechanisms associated with fall accidents and more specifically, the movement profiles that may represent the cogent behavior of the locomotor system that may be amendable to rehabilitation and intervention strategies. In this light, this Thesis is focused on better understanding the factors influencing dynamic stability measure (as measured by Lyapunov exponents) during over-ground ambulation utilizing wireless Inertial Measurement Unit (IMU). Four pilot studies were conducted: the First study was carried out to verify if IMU system was sophisticated enough to determine different load-carrying conditions. Second, to test the effects of walking inclinations, three incline levels on gait dynamic stability were examined. Third, tested whether different sections from the total gait cycle can be stitched together to assess LDS using the laboratory collected data. Finally, the fourth study examines the effect of “stitching” the data on dynamic stability measure from a longitudinally assessed (3-day continuous data collection) data to assess the effects of free-range data on assessment of dynamic stability. Results indicated that load carrying significantly influenced dynamic stability measure but not for the floor inclination levels – indicating that future use of such measure should further implicate normalization of dynamic stability measures associated with different activities and terrain conditions. Additionally, stitching method was successful in obtaining dynamic stability measure utilizing free-living IMU data. / Dissertation/Thesis / Masters Thesis Biomedical Engineering 2017

Title: Evaluation of the dynamic postural stability of competitive epee fencers. Objectives: The aim of this work is to objectively evaluate and compare postural stability of fencers by Neurocom EquiTest computerized dynamic posturography. Methods: The work has the character of a quantitative observational study, the aim of which was to assess and compare postural stability in sport fencers. A total of 63 probands took part in the research. The experimental group consisted of 9 fencers and 7 fencers in the age range of 20-29 years (average age = 24.19, SD = 2.70). The remaining 47 individuals formed a control group (23 men, 24 women, mean age = 25.22, SD = 2.20). Postural stability was assessed using a Neurocom SMART EquiTest. A complete range of 7 tests was used - Sensory organization test (SOT), Adaptation test (ADT), Motor control test (MCT), Unilateral stance (US), Limits of stability (LOS), Rythmic weight shift (RWS) and Weight bearing squat (WBS). In the experimental group, then additional balance tests - Single leg standing test and Stork test. The measured data were statistically processed and compared in the program R. Descriptive elements were determined for the data used for this work - mean, median, standard deviation. Data normality was assessed by the Shapiro-Wilk test. The...

Society of today is struggling with both large amounts of emissions as well as congestion on the roads. For this reason, AFRY in collaboration with Volvo GTT is working on develop and implement longer and heavier transports in traffic network. These combinations are called high capacity transport and have high performance-based demands. Dynamic stability is one demand that can be improved for the DUOCAT, which is a high capacity transport combination. The hypothesis is that a displacement backward in the direction of travel of the v-stay can improve the dynamic stability. The v-stay is a component of the rear wheel suspension and has an important function regarding dynamic stability by absorbing lateral forces. To achieve better dynamic stability, the goal is to create counter steering on the rear axle of the DUO-CAT through small design changes on the v-stay. The suggestion from Volvo is to move the v-stay backward in the direction of travel, which in this thesis has become the focus in both concept generation and design work. The thesis includes development of new concepts of the v-stay. An extensive evaluation process consisting of dynamic analysis was carried out in PTC Creo Parametric, which made it possible to compare the new concepts with the current v-stay. An important part of the thesis is to obtain a simplified model that simulate the physical conditions. The delimitations are to examine lateral acceleration with load on the axle and friction between asphalt and wheels. The maneuver in the analyses emulates a quick lane change at 80 km/h. This has resulted in a new concept that includes the current v-stay where only the position on the frame and axle is changed with the help of new fastening components. The new concept provides an increased counter steering of 6%. The conclusion is that a displacement backwards in the direction of travel of the vehicle gives an increased counter steering. Future work is required to achieve the desired improved steering and safety requirements.

The primary goal of human locomotion is to translate the body from point A to point B, but humans must have the variability and stability to adapt and recover from constraints they may encounter. The overarching aim of this dissertation was to investigate how constraints arising from external factors (i.e., military load carriage and speed) and internal factors (i.e., hip pain) affect kinematic variability and local dynamic stability of gait. In study 1, I focus on using traditional biomechanical measures to investigate if females and males use different gait mechanics when carrying military-relevant loads, as females and males are known to use different mechanics when walking with no load. In this study, I found that females and males do use different gait mechanics when walking with military-relevant loads. Females make kinematic adaptations at the ankle and knee while males make kinematic adaptations at the hip. The differences in adaptations between females and males may be related to females’ greater risk of injury when carrying load. In study 2, I used the same cohort to investigate how military-relevant loads affect the kinematic variability and local dynamic stability of gait. I found that kinematic variability and local dynamic stability were similarly affected by load. Participants had greater kinematic variability and decreased local dynamic stability when carrying loads, which may indicate an increased risk of falling while carrying load. I also found that local dynamic stability increased with increased walking speed at all loads in the mediolateral and anteroposterior directions. However, decreased stability was detected in the vertical direction, which may require increased energy expenditure. The results of this study indicate that walking faster with increased loads may be more stable, but less energy efficient. In study 3, I investigated the how kinematic variability and local dynamic stability were affected in individuals with hip pain and a history of developmental dysplasia. I found that kinematic variability and local dynamic stability were not similarly affected in these individuals. I found that kinematic variability was greater in individuals with hip pain compared to healthy controls, but there was no difference in local dynamic stability between groups. The overall finding of this dissertation is that the relationship between kinematic variability and local dynamic stability may be dependent on the factor investigated. / 2020-07-06T00:00:00Z

While tremendous advances have been made in prosthesis technology, a greater understanding of amputee gait is needed, especially among amputees in developing countries. Field studies as well as prosthesis technology in developing countries are limited due to barriers associated with equipment and resources availability. Furthermore, individuals with lower limb amputation experience increased difficulty walking and a higher fall rate compared to non-amputees, which may be exacerbated by environment, terrain, or prosthesis componentry. Due to the importance of walking on various terrain for increased quality of life as well as the differences between prosthesis technology available in developing and developed countries, a better understanding of amputee gait on underdeveloped outdoor terrain is needed. We began to address these needs with three studies that explored factors that influenced and predicted amputee gait on realistic end-user outdoor terrain. First, we investigated the effects of environment (i.e. indoor laboratory or outdoor natural walking path), terrain, and amputation level on energy expenditure and dynamic stability while walking among lower limb amputees and non-amputees. We found that terrain and amputation level affected amputee energy expenditure and stability while environment and specific uneven terrain type had minimal effects. These results may guide future work investigating the effects of terrain in laboratory-based studies. Second, we investigated the ability to predict quantitative measures of amputee gait on outdoor underdeveloped terrain from laboratory-based measurements. We found individual participant characteristics and easily accessible measures of indoor gait were as or more effective at predicting energy expenditure and dynamic stability than gait measures requiring greater experimental and analytical resources. These results may offer a tool for researchers to assess performance among amputees in various settings without the need for expensive and technical equipment. Third, we examined the effect of a low-cost prosthetic knee joint on amputee gait. Specifically, we investigated the effects of on energy expenditure, gait stability, and perceptions of the low-cost prosthetic knee joint while walking on indoor and outdoor terrains. We found evidence that the low-cost knee increased energy expenditure and increased some characteristics of dynamic stability while decreased others. Furthermore, we also identified key insights among amputees about the performance of the low-cost prosthetic knee joint that could aid in future design modifications of the knee. Together, these studies help to clarify differences in walking performance between laboratory and outdoor terrains among lower limb amputees, help circumvent the challenges of obtaining quantitative gait measures during field studies in developing countries and may help guide the future design and use of low-cost prosthetic knee technology. / Doctor of Philosophy / While tremendous advances have been made in prosthesis technology, a greater understanding of how lower limb amputees walk (i.e. amputee gait) is needed, especially among amputees in developing countries. Studies in the field as well as the devices that amputees where to walk (prosthesis technology) in developing countries are limited due to barriers associated with equipment and resources availability. Furthermore, individuals with lower limb amputation experience increased difficulty walking and a higher fall rates compared to non-amputees, which may be exacerbated by environment, terrain, or components of the prosthesis. Due to the importance of walking on various terrain for increased quality of life as well as the differences between prosthesis technology available in developing and developed countries, a better understanding of how amputees walk on uneven outdoor terrain is needed. We began to address these needs with three studies that explored factors that influenced and predicted how amputees walk on realistic end-user outdoor terrain. First, we investigated the effects of environment (i.e. indoor laboratory or outdoor natural walking path), terrain, and amputation level on energy expenditure and walking stability among lower limb amputees and non-amputees. We found that terrain and amputation level affected amputee energy expenditure and stability while environment and specific uneven terrain type had minimal effects. These results may guide future work investigating the effects of terrain in laboratory-based studies. Second, we investigated whether we could predict amputee walking performance on outdoor underdeveloped terrain from laboratory-based measurements. We found individual participant characteristics and easily accessible performance measures were as or more effective at predicting energy expenditure and stability than performance measures requiring greater experimental and analytical resources. These results may offer a tool for researchers to assess performance among amputees in various settings without the need for expensive and technical equipment. Third, we examined the effect of a low-cost prosthetic knee joint on amputee gait. Specifically, we investigated the effects of on energy expenditure, gait stability, and perceptions of the low-cost prosthetic knee joint while walking on indoor and outdoor terrains. We found evidence that the low-cost knee increased energy expenditure and increased some characteristics of stability while decreased others. Furthermore, we also identified key insights among amputees about the performance of the low-cost prosthetic knee joint that could aid in future design modifications of the knee. Together, these studies help to clarify differences in walking performance between laboratory and outdoor terrains among lower limb amputees, help circumvent the challenges of obtaining quantitative gait measures during field studies in developing countries and may help guide the future design and use of low-cost prosthetic knee technology.

Introduction: Asymmetric gait is prevalent among older adults as well as in people with gait pathologies (e.g., Parkinson’s disease, following a stroke) and has been linked to a higher risk of falls. While a certain level of gait asymmetry is present in healthy young adults, the simulation of larger asymmetry in this population provides information about efficient strategies to regulate dynamic stability. Research investigating gait asymmetry has described spatiotemporal and kinematic strategies. However, limited information is available regarding changes in gait kinetics. Research objectives: This thesis aims to determine the gait control strategies utilized by young adults to regulate simulated gait asymmetry combined with different arm movement amplitude. We hypothesized that the hip joint would be the most affected by different arm swing conditions and asymmetric gait. We also hypothesized that asymmetric gait and active arm swing would lead to increased variability in the lower-limb movements. Methods: Fifteen healthy young adults (23.4±2.8 years, 7 Females) walked with three arm swing conditions (held, normal, and active) during symmetric and asymmetric walking conditions. The CAREN-extended System (Motek Medical, Amsterdam, NL) was used for data collection. Outcome measures included step length and width mean and variability (meanSD), vertical ground reaction forces, and lower-limb joint moment impulse mean and variability (meanSD) in the sagittal and frontal planes. Results: When comparing arm swing conditions, the active arm swing led to an increase in step width variability, vertical ground reaction forces, hip and knee variability in the sagittal plane, ankle abduction moment for the fast leg, as well as in knee variability in the frontal plane. As for gait symmetry, the asymmetric condition led to increased step width for the fast and slow legs and increased vertical ground reaction forces for the slow leg. The asymmetric condition further prompted adjustments in the frontal and sagittal planes, particularly at the ankle and hip joints during the braking phase, and in the knee joint during the propulsion phase phases when compared to the symmetric walking condition. Conclusion: Findings suggest that participants increased hip activity to control the effect of arm motion on the trunk to minimize adaptations in the lower-limb joints. The asymmetry condition demonstrated that participants searched for flexible lower-limb strategies aimed at minimizing bilateral differences between the fast and slow legs during asymmetric walking.

PURPOSE. To determine the effects of blurring vision on whole-body center-of-mass (CM) dynamics and foot-clearance parameters in elderly individuals performing a single step up to a new level. METHODS. Twelve healthy subjects (mean age, 72.3 ±4.17 years) performed a single step up to a new level (heights of 73 and 146 mm). Trials were undertaken with vision optimally corrected and with vision diffusively blurred by light-scattering lenses (cataract simulation). CM and foot-clearance parameter data were assessed by analyzing data collected by a five-camera, three-dimensional (3-D) motion analysis system. RESULTS. When vision was blurred, subjects took 11% longer to execute the stepping task (P < 0.05), mediolateral displacement of the point of application of the ground reaction force vector (i.e., weighted average of all pressures over the area in contact with the ground; the so called center of pressure, CP) decreased from 37.6% of stance width to 28.3% (P < 0.01), maximum distance between the mediolateral position of the CM and CP decreased by 9.8 mm (P < 0.01), and toe clearance (distance between tip of shoe and edge of step) increased in both the horizontal (28%) and vertical (19%) direction (P < 0.05). CONCLUSIONS. These findings suggest that when vision was blurred, subjects used a twofold safety-driven adaptation: First, to increase dynamic stability they ensured that the horizontal position of their CM was kept close to the center of the base of support and second, they increased horizontal and vertical toe clearance while swinging their lead limb forward to reduce the risk of tripping.

When a power system is subjected to a disturbance, the power flow changes, leading to deviations in the synchronous generator rotor angles. The rotor angle deviations propagate as electromechanical waves (EMWs) throughout the power system. These waves became observable since the development of synchrophasor measurement instruments. The speed of EMW propagation is hundreds of miles per second, much less than the electromagnetic wave propagation speed, which is the speed of light. Recently, with the development of renewable energy resources and a growth in using HVDC and FACTS devices, these waves are propagating slower, and their impacts are more considerable and complicated. The protection system needs a control system that can take suitable action based on local measurements to overcome the results of power system faults. Therefore, the dynamic behavior of power systems should be properly observed. The EMW propagation in the literature was studied using assumptions such as constant voltage throughout the entire power system and zero resistances and equal series reactances for the transmission lines. Although these assumptions help simplify the power system study model, the model cannot capture the entire power system's dynamic behaviors, since these assumptions are unrealistic. This research will develop an accurate model for EMW propagation when the system is facing a disturbance using a continuum model. The model includes a novel inertia distribution. It also investigates the impacts of voltage changes in the power system on EMW behaviors and when these impacts are negligible. Furthermore, the impacts of the internal reactances of synchronous generators and the resistances of transmission lines on EMW propagation are explored. / Doctor of Philosophy / Power systems, essential for electricity supply, undergo disturbances causing changes in power flow and synchronous generator behavior. These disturbances create electromechanical waves (EMWs) that influence system dynamics. Recent advancements, including renewable energy integration and new technologies, alter EMW behavior, posing challenges for control and protection systems. Existing studies simplify models, limiting their accuracy. This research aims to develop a realistic EMW propagation model considering factors like novel inertia distribution, voltage changes, and internal generator properties. This work addresses the evolving power landscape, enhancing our understanding of power system dynamics for improved control and reliability.

Older adults, especially older women, produce less muscular power than young adults, due primarily to slower maximal contractile velocity. These decrements may lead to increased fall risk in older women and can be exacerbated by fatigue. Recently, a 32 min walking task (32MWT) was shown to elicit fatigue in older women. The purpose of this study was to determine whether knee extensor (KE) maximal velocity is related to dynamic stability (margin of stability, MoS) in young and older women pre- and post-32MWT. METHODS: Nine young (Y; 24.3+1.1years, mean±SE) and 17 older (O; 71.1±1.1years) healthy women completed 2 testing sessions on separate days: 1) electrically-stimulated and voluntary KE muscle characteristics were measured to determine rates of force development and relaxation (RFD, RFR) and half-relaxation times (T1/2) as well as peak isometric torque, power generated at 270 deg∙s-1, and maximal contractile velocity of the dominant leg; 2) MoS was measured using a forward fall test at 25% body weight; 10 baseline trials were performed. On both testing days, the 32MWT was performed following baseline measures. All variables of interest were then collected during 30 min of recovery. RESULTS: MoS was higher in young than older women (Y: 0.044±0.021m, O: -0.130±0.033m, p=0.001) and increased over the 10 baseline trials in both groups (p=0.01). Post-32MWT, both groups showed decreased isometric torque (Y: p=0.04, O: p-1 (Y: p=0.05, O: p=0.01), and unaltered MoS (Y: p=0.34, O: p=0.52) and maximal velocity (Y: p=0.22, O: p=0.54). Additionally, T1/2 was lower post-32MWT in older (p20.32) or post-32MWT (r20.22) in either group. CONCLUSIONS: The 32MWT elicited fatigue in some contractile variables, but improved or had no effect on others. Maximal KE contractile velocity was not associated with MoS in young or older women. Future studies are needed to determine other potential mechanisms of lower MoS in older than young women. The increase in MoS over 10 baseline trials should be considered by researchers when using the forward fall test to evaluate real-world fall risk.