The purpose of this thesis is to investigate the reaction to a purely unexpected slip during gait termination and subsequent experiences stopping on the slippery surface in participants who are young and healthy, older and healthy and who have Parkinson’s disease while on traditional dopamine-replacement medication. Gait termination requires control of the forward momentum of the body’s centre of mass (COM). This forward momentum must be dissipated and the COM held within a newly formed base of support. The challenge of stopping on a slippery surface involves maintaining stability while transitioning from steady-state locomotion to steady-state stance. Experience with a slippery surface changes postural and gait characteristics to diminish the perturbing effect of the slip. The magnitude of the slip response diminishes quickly as the movement becomes more efficient. Our investigations revealed a typical slip response to a purely unexpected slip during gait termination including a lowering of the COM, an increased muscular response to support the body, a shortened step and an arm raise. Knowledge of and experience with the slippery surface quickly changed the slip response to reduce the perturbing effect of the slip and also to increase the efficiency of the response while smoothly transitioning from steady-state locomotion to gait termination. Parkinson’s disease impairs balance control, the ability to switch between motor tasks and also to stop within two steps. The need for a voluntary change in motor programs along with difficulty stopping and increased instability makes gait termination a potentially difficult task for someone with Parkinson’s disease (PD). The participants with PD used a slower, safer strategy to stop on non-slippery surfaces to compensate for their instability compared to age-matched controls. When a slip was first introduced during gait termination, the participants with PD continued to be less stable in the plane of progression than the control group. Despite the instability, the PD group was still able to integrate a balance-correcting response into a voluntary gait termination program. The ability to generate adaptive strategies to integrate the balance-correcting response into a voluntary gait termination program over multiple trials does not appear to be affected by PD; both the control group and PD group showed behavioural modifications according to repeated exposures to the slippery surface. Although participants with PD seemed slightly less stable and walked slower, their behavioural adaptations were similar to the control group.

The purpose of this thesis is to investigate the reaction to a purely unexpected slip during gait termination and subsequent experiences stopping on the slippery surface in participants who are young and healthy, older and healthy and who have Parkinson’s disease while on traditional dopamine-replacement medication. Gait termination requires control of the forward momentum of the body’s centre of mass (COM). This forward momentum must be dissipated and the COM held within a newly formed base of support. The challenge of stopping on a slippery surface involves maintaining stability while transitioning from steady-state locomotion to steady-state stance. Experience with a slippery surface changes postural and gait characteristics to diminish the perturbing effect of the slip. The magnitude of the slip response diminishes quickly as the movement becomes more efficient. Our investigations revealed a typical slip response to a purely unexpected slip during gait termination including a lowering of the COM, an increased muscular response to support the body, a shortened step and an arm raise. Knowledge of and experience with the slippery surface quickly changed the slip response to reduce the perturbing effect of the slip and also to increase the efficiency of the response while smoothly transitioning from steady-state locomotion to gait termination. Parkinson’s disease impairs balance control, the ability to switch between motor tasks and also to stop within two steps. The need for a voluntary change in motor programs along with difficulty stopping and increased instability makes gait termination a potentially difficult task for someone with Parkinson’s disease (PD). The participants with PD used a slower, safer strategy to stop on non-slippery surfaces to compensate for their instability compared to age-matched controls. When a slip was first introduced during gait termination, the participants with PD continued to be less stable in the plane of progression than the control group. Despite the instability, the PD group was still able to integrate a balance-correcting response into a voluntary gait termination program. The ability to generate adaptive strategies to integrate the balance-correcting response into a voluntary gait termination program over multiple trials does not appear to be affected by PD; both the control group and PD group showed behavioural modifications according to repeated exposures to the slippery surface. Although participants with PD seemed slightly less stable and walked slower, their behavioural adaptations were similar to the control group.

Yes / To terminate gait, the mechanical work-done by the lower-limbs is likely to be predominantly negative but how such work is produced/completed has not previously been investigated. The aim of this study was to determine the amount of negative mechanical (external) work-done by the lower-limbs, along with the associated joints (muscle) work, to terminate gait and how these work contributions were affected by a change in surface angle. Eight males completed terminations on the level floor and a declined ramp. Negative mechanical limb-work (limbW(−ve)) was computed (each orthogonal direction) as the dot-product of the ground-reaction-force and centre-of-mass (CoM) velocity. Inverse dynamics was used to calculate ankle, knee and hip negative joints (muscle) work (Wj(−ve)). Measures were determined for each limb for the two-locomotor steps of gait termination. The trailing-limb did 67% (−0.386 J/kg) of the overall limbW(−ve) to terminate gait on the level; and this increased to 74% (−0.451 J/kg) for ramp trials. Wj(−ve) was greater for the trailing- (ankle −0.315; knee −0.357; hip −0.054 J/kg) compared to terminating- limb (ankle, −0.063; knee −0.051; hip −0.014 J/kg), with the increases in ankle Wj(−ve) being temporally associated with increases in perpendicular limbW(−ve). Wj(−ve) increased on both limbs for declined compared to level surface, particularly at the knee (declined −0.357, level −0.096 J/kg), with such increases being temporally associated with increases in parallel limbW(−ve). These findings provide new perspectives on how the limbs do work on the CoM to terminate gait, and may be helpful in designing prosthetic limbs to facilitate walking on ramps. / ZA was funded by the Higher Committee of Education Development in IRAQ (HCED).

Yes / Walking down ramps is a demanding task for transfemoral-amputees and terminating gait on ramps is even more challenging because of the requirement to maintain a stable limb so that it can do the necessary negative mechanical work on the centre-of-mass in order to arrest (dissipate) forward/downward velocity. We determined how the use of a microprocessor-controlled limb system (simultaneous control over hydraulic resistances at ankle and knee) affected the negative mechanical work done by each limb when transfemoral-amputees terminated gait during ramp descent. Methods: Eight transfemoral-amputees completed planned gait terminations (stopping on prosthesis) on a 5-degree ramp from slow and customary walking speeds, with the limb's microprocessor active or inactive. When active the limb operated in its ‘ramp-descent’ mode and when inactive the knee and ankle devices functioned at constant default levels. Negative limb work, determined as the integral of the negative mechanical (external) limb power during the braking phase, was compared across speeds and microprocessor conditions. Findings: Negative work done by each limb increased with speed (p < 0.001), and on the prosthetic limb it was greater when the microprocessor was active compared to inactive (p = 0.004). There was no change in work done across microprocessor conditions on the intact limb (p = 0.35). Interpretation: Greater involvement of the prosthetic limb when the limb system was active indicates its ramp-descent mode effectively altered the hydraulic resistances at the ankle and knee. Findings highlight participants became more assured using their prosthetic limb to arrest centre-of-mass velocity. / ZA is funded by the Higher Committee of Education Development in IRAQ (HCED student number D13 626).

The major objective of this thesis was to investigate how the use of a recently developed microprocessor-controlled limb system altered the negative mechanical work done by the intact and prosthetic limb when trans-femoral amputees terminated gait. Participants terminated gait on a level surface from their self-selected walking speed and on declined surface from slow and customary speeds, using limb system prosthesis with microprocessor active or inactive. Limb negative work, determined as the integral of the negative mechanical (external) limb power during the braking phase, was compared across surface, speed and microprocessor conditions. Halting gait was achieved predominantly from negative work done by the trailing/intact. Trailing versus leading limb mechanical work imbalance was similar to how able body individuals halted gait. Importantly, the negative limb work performed on the prosthetic side when terminating gait on declined surface was increased when the microprocessor was active for both slow and customary speeds (no difference on level surface) but no change on intact limb. This indicates the limb system’s ‘ramp-descent mode’ effectively/dynamically altered the hydraulic resistances at the respective joints with evidence indicating changes at the ankle were the key factor for increasing the prosthetic limb negative work contribution. Findings suggest that trans-femoral amputees became more assured using their prosthetic limb to arrest body centre of mass velocity when the limb system’s microprocessor was active. More generally findings suggest, trans-femoral amputees should obtain clinically significant biomechanical benefits from using a limb system prosthesis for locomotion involving adapting to their everyday walking where adaptations to an endlessly changing environment are required. / Higher Committee of Education Development in IRAQ (HCED)

Made available in DSpace on 2016-06-02T20:19:14Z (GMT). No. of bitstreams: 1 3062.pdf: 2064067 bytes, checksum: 9736110404bad178c5bdecf3fbb8c52a (MD5) Previous issue date: 2010-02-14 / Financiadora de Estudos e Projetos / The gait initiation is set to transition from standing posture to the first step to reversing cyclical, and involves a motor program mediated by adjustments preparations necessary to propel the body forward (MELOUIN ET AL, 2000). Studies that approach the initialization mostly in the adult population have aimed to understand the limitations in postural disorders, aging and what little is in the child population also has a focus on disease and how this process occurs not because of the development of walking independent. This study aimed to describe how the gait initiation process occurs and how it changes as occurs the development of independent walking. We evaluated 29 subjects into three groups: G1 (15 months - 10 subjects), G2 (3 years - 9 subjects) and GA (Adult - 10 subjects). The variables were analyzed: amplitude of oscillation of the center of force toward the average side (COFML) and anterior posterior (COFAP) and average speed and VELAP VELML. The nonparametric Kruskal Wallis test was used to detect differences between groups; the significance level was p &#8804; 0.05%. Results of gait initiation: COFAP (cm) there was no statistically significant differences between groups. However, both groups showed significant differences in the COFML behavior (7.79cm = G1, G3 = 7.46cm, GA = 3.25cm, p = 0.01). Furthermore the variable VELAP (cm / s), showed no statistically significant difference between groups, as well as the variable VLML. Results of gait termination: variables results COFAP (G1 = 11.15 cm, G3 = GA = 8.69 cm and 5.17 cm) and COFML (G1 = 7.83 cm, G3 = 8 cm and 4.86 cm = GA) showed no statistically significant differences when purchased between the three groups proposed both as a platform to platform 2. VELAP (G1 = 4.13 cm / s, G3 = 3.16 cm / GA = 3.26 cm / s) and VELML (G1 = 9.74 cm / s, G3 = 5.72 cm / s and GA = 2, 49 cm / s) were not statistically different during the completion of the gait termination, the results indicated the importance that the strength center behavior and the ability to deal with the gravitational field during the gait initiation and how this process changes with the experience of walking independently. / A inicialização de marcha é definida como transição da postura em pé ao primeiro passo a marcha cíclica, e envolve um programa motor mediado por ajustes preparatórios necessários para propulsionar o corpo para frente (MELOUIN ET AL,2000). Os estudos que abordam a inicialização em sua maioria em população adulta têm como objetivo compreender as limitações posturais em patologias e no envelhecimento e o pouco que se encontra em população infantil também tem o foco em patologias e não como este processo ocorre em função do desenvolvimento do andar independente. Este estudo teve por objetivo descrever como ocorre o processo de inicialização da marcha e como este muda à medida que ocorre o desenvolvimento do andar independente. Foram avaliados 29 sujeitos em três grupos G1 ( 15 meses 10 sujeitos), G2 ( 3 anos 9 sujeitos) e GA (adulto 10 sujeitos). As variáveis analisadas foram: amplitude de oscilação do centro de força na direção médio lateral (COFML) e antero posterior (COFAP) e velocidade média VELAP e VELML. O teste não paramétrico de Kruskal Wallis foi utilizado para detectar diferenças entre os grupos, o nível de significância foi de p &#8804; 0,05%. Resultados Inicialização da marcha: COFAP (cm) não houve diferenças estatisticamente significativas entre os grupos. Porém, ambos os grupos apresentaram diferenças significativas para o comportamento da COFML (G1 = 7.79cm, G3 = 7.46cm, GA= 3.25cm e p= 0.01). Por outro lado a variável VELAP (cm/s), não apresentou diferença estatisticamente significativa entre os grupos,assim como a variável VLML. Resultados Finalização da marcha os resultados das variáveis COFAP (G1 = 11,15cm, G3 = 8,69 cm e GA = 5,17 cm) e COFML (G1 = 7,83cm , G3 = 8cm e GA = 4,86 cm) não apresentaram diferenças estatisticamente significativas quando compradas entre os três grupos propostos tanto para a plataforma 1 quanto para a plataforma 2. VELAP (G1 = 4,13cm/s, G3 = 3,16cm/s e GA = 3,26cm/s) e VELML(G1 = 9,74 cm/s, G3 = 5,72 cm/se e GA = 2,49 cm/s), não foram estatisticamente diferentes durante a finalização do marcha Como conclusão, os resultados indicaram importância que o comportamento do centro de força e a capacidade de lidar com o campo gravitacional durante a inicialização da marcha e como este processo muda de acordo com a experiência do andar independente.