Tesis sobre el tema "Cost of walking"

Diabetes mellitus is a serious worldwide disease characterised by pathological metabolism of sugars. Diabetic peripheral neuropathy (DPN) is a common complication of diabetes involving dysfunction of peripheral nerves. Diabetes is known to alter a number of biomechanical aspects of gait, but it remains unknown as to whether these alterations could impact upon the metabolic cost of walking (CoW). The aim of this thesis was to investigate the CoW in people with diabetes and examine biomechanical factors that could contribute to explaining any potential differences. Data were generated from three groups: patients with DPN (n=14), patients with diabetes but without peripheral neuropathy (DM, n=22), and controls without diabetes (Ctrl, n=31). Gait assessment was performed using a Vicon motion analysis system and Kistler force plates while participants walked at a range of matched speeds (between 0.6 and 1.6 m/s). Oxygen consumption was measured continuously whilst participants walked on a motor-driven treadmill at the range of matched walking speeds. Ultrasonographic imaging data from the plantarflexor muscle-tendon complex (MTC) were collected in vivo during walking to determine MTC properties. Magnetic resonance imaging of the ankle joint in the standing position was used to quantify the internal leverage around the ankle. Isometric plantarflexor maximal voluntary contraction strength was measured using a dynamometer. The CoW was significantly higher in the DPN group across a range of matched walking speeds and also in the DM group at selected speeds, compared to Ctrl. Despite the higher CoW in patients with diabetes, concentric lower limb joint work was significantly lower in DM and DPN groups compared to Ctrl. A greater value for the effective mechanical advantage (EMA) at the ankle joint was found in the DPN and DM groups compared to Ctrl, meaning that the ankle plantarflexor muscles developed relatively lower forces to generate a given joint moment compared to Ctrl. The increased EMA was mainly caused by a smaller external moment arm of the ground reaction force in the DPN and DM groups compared to Ctrl. The DPN group reduced the joint moment at the ankle during walking by applying the ground reaction force more proximally on the foot, or at an angle directed more towards the ankle, thereby reducing the external moment arm and increasing the EMA around the ankle. The DPN group demonstrated significantly less Achilles tendon elongation during walking, higher stiffness and higher hysteresis compared to Ctrl. These properties mean that the Achilles tendon would store and release less energy in the DPN group during walking, requiring more work from the plantarflexor muscles. Vertical displacement of the centre of mass during walking was not different between groups and is therefore unlikely to be a factor in itself that contributes towards the increased CoW in people with diabetic neuropathy. A higher cumulative joint work resulting from an increased cadence may contribute to the higher CoW in patients with diabetes, along with a reduced elastic energy contribution from the Achilles tendon.

This thesis investigated the cost-effectiveness of a 12-month supervised aerobic walking program with or without a behavioural intervention and an educational pamphlet, compared to an unsupervised/self-directed educational pamphlet intervention, among individuals with moderate osteoarthritis (OA) of the knee. Analyses included an economic evaluation to assess the cost effectiveness of the two walking interventions from both the societal and Canadian provincial/territorial health care payer perspectives. A value of information analysis exploring the potential value of future research was also performed. Results revealed that the unsupervised/self-directed intervention was the most cost-effective approach given that it cost the least to implement and participants had higher quality-adjusted life years (QALYs). Walking, either supervised in a community setting, or unsupervised in a setting such as the home, may be a favourable non-pharmacological option for the management of OA of the knee. The thesis concludes with a policy discussion relating to the funding of non-pharmacological therapies.

The physiological energy requirements of prosthetic gait in lower-limb amputees have been observed to be significantly greater than those for able-bodied subjects. However, existing models of energy flow in walking have not been very successful in explaining the reasons for this additional energy cost. Existing mechanical models fail to capture all of the components of energy cost involved in human walking. In this thesis, a new model is developed that estimates the physiological cost of walking for an able-bodied individual; the same cost of walking is then computed using a variation of the model that represents a bi-lateral below-knee amputee. The results indicate a higher physiological cost for the amputee model, suggesting that the model more accurately represents the relative metabolic costs of able-bodied and amputee walking gait. The model is based on a two-dimensional multi-body mechanical model that computes the joint torques required for a specified pattern of joint kinematics. In contrast to other models, the mechanical model includes a balance controller component that dynamically maintains the stability of the model during the walking simulation. This allows for analysis of many consecutive steps, and includes in the metabolic cost estimation the energy required to maintain balance. A muscle stress based calculation is used to determine the optimal muscle force distribution required to achieve the joint torques computed by the mechanical model. This calculation is also used as a measure of the metabolic energy cost of the walking simulation. Finally, an optimization algorithm is applied to the joint kinematic patterns to find the optimal walking motion for the model. This approach allows the simulation to find the most energy efficient gait for the model, mimicking the natural human tendency to walk with the most efficient stride length and speed.

Human legged locomotion has been widely studied from both mechanical and bioenergetics points of view, however some aspects are still unaddressed and this thesis aimed to analysed some of them. One of the two methods for calculating muscular work during locomotion, which is an interesting parameters that can describe locomotion and subjective featuring, concerns the body centre of mass (BCoM) movements. The BCoM is the ideal point of the body where all forces act, and especially in a multi segment body as the human body, it is much easier and useful to calculate and follow its trajectory as the movement of the whole body. In order to compute BCoM two methods can be used: a double integration of the ground reaction forces, the forces exerted by feet when in contact to the ground, based on Newton’s second law, which is considered the gold standard, and called Direct Dynamics; and the weighted mean of segments centre of mass (COM) obtained by motion analysis, called Inverse Dynamics. Segments mass and COM location are based on anthropometric tables, which are scaled on subjects’ lengths; this is an approximation and assumes that segments are rigid, introducing potential errors. Even if there is not a complete 3D validation of Inverse Dynamics as a function of speed in the human gaits, Inverse and Direct Dynamics are often used interchangeably. In the first part of the thesis Inverse and Direct Dynamics in the human locomotion repertoire were compared in order to analyse different models, based on different anthropometric tables, and validate Inverse Dynamics. BCoM trajectory in walking, running and skipping is well described by Inverse Dynamics models employing a whole body marker set, where the main body segments are considered for BCoM calculation. On the contrary, simplified estimation models employing few markers, such as just one marker on the trunk or the mean of the pelvis, poorly match Direct Dynamics trajectory. Same results come from the further analysis of muscular work, where whole body models better describe and match Direct Dynamics data. Some interesting observations emerged from these analyses: i) two anthropometric tables with quite different segments definition reach the same results; ii) whole body models of Inverse Dynamics well matched Direct Dynamics values, validating this methods, whereas poor models should not be employed anymore; iii) the difference between Inverse and Direct Dynamics in the same gait is almost speed independent highlighting a systematic error, and among gaits it shows the same trend; iv) race walking BCoM trajectory cannot be described with any Inverse Dynamics models, therefore only ground reaction forces should be used for computation. Skipping is the third paradigm of human locomotion. Differently from walking and running, it was only investigated on level ground, addressing the much expensive cost of transport as the reason for its under use in day life activity; conversely it was displayed by astronauts of Apollo missions on the Moon. In the second part of this thesis the mechanics and bioenergetics of skipping on gradient was investigated since Ed Mitchell during Apollo 14 mission explicitly said “That nice skipping gait that I liked was very easy to do going downhill”. Gradient range was ±15%, the range of gradient presents on the Moon. On Earth skipping cost is higher than walking and running at all gradients and it decreases with speed, differently from the other gaits no minimum was found during downhill skipping, and it is impossible to skip at positive gradient steeper than 5% due to muscular demand and consequent fraction of metabolic power. When analysing mechanical parameters, the work done by muscles to move BCoM (WEXT) and the work done to accelerate limbs with respect to BCoM (WINT), skipping changes are similar to running with WEXT decreasing with downhill gradient and increasing speed, whereas WINT increases with speed. These results show that skipping on gradient can be performed on Earth only downhill due to the great metabolic demand. However, skipping cost of transport is always higher than walking and running at the same slopes. Based on these findings and astronauts’ choices, we could expect that gravity plays an important role on skipping and locomotion cost of transport, which are analysed and discussed in the third part of this thesis. Low gravity locomotion can be studied on Earth with different methods, the gold standard is the parabolic flight, since with the adequate angle of the airplane parabola it is possible to obtain gravity levels ranging from hypo-gravity (including 0 g) to hyper-gravity. However the time available at low gravity simulation is only about 30 seconds, which is too short for metabolic measurements. The second most used method is based on the body weight suspension, where subjects are unloaded of the desired body weight by the suspension of the body via bungee cords or springs. We re-vamped the Margaria’s low- gravity ‘cavedium’ with a treadmill and two bungee cords free to stretch until 16 m and let subjects walk, run and skip on a range of speed with Moon and Mars gravity, in order to study cost of transport and biomechanical parameters. Walking range of speed decreases with gravity and cost of transport decreases by 18% in hypo-gravity; higher decrements are shown in bouncing gaits, running and skipping. On the Moon their cost is the same and comparable with terrestrial walking values. Being on Earth was almost 40% higher than running, skipping shows the best decrease and a threefold gain in operative speed. This means that on the Moon human can skip three times faster than on Earth with the same metabolic power, whereas running gain is only twofold. Mechanically these cost changes can be explained by a reduction in pendulum-like recovery of energy in walking that needs a higher muscular work, whereas in skipping it is not shown. Moreover WEXT is lower in low gravity and a greater reduction of WINT in skipping compared with running can partially explain the major reduction in skipping cost. Another interesting aspect related to gait mechanics regards stability, and when the surface is slippery, as on the Moon due to regoliths, balance during support phase becomes an important issue. Skipping, compared to running, involves a shorter stance phase and also a double support, in which the trajectory of the flight can be adjusted. Moreover higher vertical forces on the ground and a greater angle at take off let the foot to be less slippery when pushing the body forward. Based on this biomechanical and bioenergetics analyses it can be concluded that human locomotion on hypo-gravity planets will be a bouncing gait and probably skipping could be preferred to running. Secondly the decrease of skipping cost up to walking values on Earth can explain the astronauts’ choice of skipping during Apollo missions.

Introduction Children with cerebral palsy (CP) often have to wear orthoses to help them walk. There is a growing body of evidence that orthotic tuning, that is, optimisation of the ground reaction forces in the lower limbs during walking, is recommended to ensure the maximum potential benefit for each child. Research demonstrates that orthoses can reduce the energy cost of walking for children with CP, but to-date there is no evidence as to whether this tuning process results in further energy efficiency or not [1]. Aim The aim of this research programme was to validate a method that would help to determine when an orthosis was optimised for each child; and then to investigate whether the use of orthoses that were optimally tuned for each child allowed a further reduction in energy cost during walking, compared with orthoses that had not been optimally tuned. Method A video vector system was used to allow visualisation of the alignment of ground reaction forces in relation to the lower limbs during walking. A simple measurement tool was validated that allowed quantification of the moment arm at the knee in stance, which was used to confirm when optimal alignment had occurred following orthotic tuning. The energy cost of walking was measured using the Total Heart Beat Index (THBI). Data were collected barefoot, with the original ‘un-tuned’ orthosis and with the final ‘tuned’ orthosis. Results Analysis of energy cost showed that for some children, energy cost was further reduced through orthotic tuning, but that this was not the case for all children. Preliminary findings suggest the influence of underlying level of disability, as determined by the GMFCS. Conclusion Orthotic tuning may help to reduce the energy cost of walking for some children with CP, especially those with greater levels of disability. Further studies with large participant numbers are warranted to further investigate this area.

Coronary heart disease (CHD) is the single largest cause of death in Australia. Lack of physical activity is a primary risk factor for CHD. The thesis aimed to quantify the efficacy of walking in reducing CHD risk. Meta-analyses were performed for the quantification with the application of random-effect meta-regression models. The thesis also aimed to quantify reductions in CHD-related direct healthcare costs, productivity loss and disease burden resulting from walking interventions in Australia, using the population attributable fraction model, the work and leisure models, and the consumer surplus model. Economic evaluations were also conducted to estimate CHD-related productivity loss using the human capital and the friction methods. The results indicated that 30 minutes of normal walking a day for 5-7 days a week compared to physical inactivity reduced CHD risk by 24%. There existed a dose-response relationship between walking and CHD risk reduction. An increment of approximately 30 minutes of normal walking a day for 5 days a week reduced CHD risk by 19%. The annual productivity loss resulting from CHD was estimated at AU$1.79 billion based on the human capital method and AU$25.05 million under the friction method. 30 minutes of normal walking a day for 5-7 days a week by the country???s ???sufficient??? walking population was shown to generate an estimated $126.73 million in net direct healthcare savings annually. The net economic savings could increase to AU$419.9 million if the whole inactive population engaged in ???sufficient??? walking. The study also found that 30 minutes of normal walking a day for 5-7 days a week reduced the burden of CHD by an estimated 25,065 DALYs and the productivity loss by AU$162.65 million annually under the leisure model. If the whole inactive population engaged in such walking, the total disease burden and productivity loss could be reduced by approximately one third. The findings present epidemiological and economic evidence in support of the national physical activity guidelines, which encourage the general public to engage in moderate physical activity including walking for a minimum of 30 minutes a day for 5-7 days a week.

A caminhada humana é um movimento importante utilizado pelo homem, porém extremamente complexo em relação aos mecanismos energéticos e mecânicos que geram este movimento. O custo energético é maior na caminhada de amputados quando comparada a caminhada de indivíduos sem restrições físicas. Variáveis mecânicas e energéticas de amputados não foram extensivamente estudadas. Nosso objetivo foi avaliar a influência de diferentes velocidades, no recovery, no custo de transporte (C), na eficiência mecânica (Eff), na transdução pendular (Rint), trabalho mecânico, na estabilidade dinâmica, bem como verificar a associação entre a estabilidade dinâmica com recovery, custo de transporte e eficiência mecânica. Participaram do estudo 10 indivíduos amputados transfemurais (com joelho hidráulico e pé em fibra de carbono). Foi realizada cinemetria 3D (quatro câmeras de vídeo) e simultaneamente a análise do consumo de oxigênio. Foram determinadas cinco velocidades de caminhada, após definir a velocidade auto selecionada. Além da velocidade auto selecionada foram definidas duas velocidades acima e abaixo das VAS. Para os dados de Recovery, custo de transporte, eficiência mecânica, transdução pendular, trabalho total, trabalho externo, travalho vertical, trabalho horizontal, trabalho interno e estabilidade dinâmica foram utilizadas rotinas desenvolvidas em Matlab®. A velocidade influencia nos parâmetros mecânicos e energéticos da caminhada de amputados transfemurais. Os maiores valores para: economia de caminhada, Recovery, transdução pendular, eficiência mecânica, trabalho mecânico interno e vertical, e estabilidade dinâmica foram obtidos na máxima velocidade de caminhada dos sujeitos. As correlações entre o coeficiente de variação do comprimento da passada e Recovery, custo de transporte e potência metabólica foram moderadas. Esses resultados são de grande relevância para a área clínica e ponderados durante o processo de reabilitação desses indivíduos.
The human walking is an important movement used by man, but extremely complex in relation to the energetic and mechanical mechanisms that generate this movement. The energy cost of gait is greater in amputees than in normal subjects. Mechanical and energetics variables in amputees have not been extensively studied. Our objective was to assess the influence of speed in recovery, cost of transport (C), mechanical efficiency (Eff), pendular transduction (Rint), mechanic parameters, dynamical stability, well as to verify agreement between dynamical stability with recovery, C, Eff and metabolic power. Materials and Methods: ten transfemoral amputees (with hydraulic knee and carbon fiber foot) were selected in the study. Simultaneously three-dimensional (3D) kinematics data (four cameras) and oxygen consumption were collected at five speeds, two above and two below self-select one. The Recovery, C, Eff, Rint, dynamical stability, were processed using Matlab software. Mechanics and energetics of amputee walking were influenced by speed. In maximal speed of amputee walking were reported greatest values, like: recovery, cost of transport (C), mechanical efficiency (Eff), pendular transduction (Rint), internal and vertical mechanical work and dynamical stability. Pearson correlation between dynamical stability and Recovery, C, Eff and metabolic power were moderate. These results are clinical relevance and should be considered during the rehabilitation of these individuals.

O acidente vascular encefálico (AVE) do tipo isquêmico representa 80% dos casos de AVE no Brasil; este é resultante da interrupção do suprimento sanguíneo ao tecido cerebral. Uma sequela decorrente da lesão do neurônio motor superior é a hemiparesia, estado caracterizado pela perda parcial da força muscular de um lado do corpo. Por sua vez, a locomoção hemiparética é característica comum após o episódio de AVE. Clinicamente os pacientes apresentam alterações no controle motor, excessiva co-ativação muscular e espasticidade, assim como mudanças nas propriedades passivas dos músculos. Além disso, os padrões cinemáticos alterados acarretam em diminuição da amplitude de movimento e consequentemente redução na velocidade de caminhada e maior dispêndio energético. Dessa maneira, um melhor entendimento de como os acometimentos segmentares afetam o trabalho mecânico total (Wtot) e o custo de transporte (C) da caminhada de indivíduos com AVE pode auxiliar na avaliação da eficácia das intervenções terapêuticas. Assim, este estudo tem como objetivo mensurar e comparar o Wtot e o C em cinco diferentes velocidades de caminhada entre sujeitos hemiparéticos crônicos decorrente do AVE e sujeitos saudáveis. A amostra foi composta por 6 pacientes com diagnóstico clínico de AVE do tipo isquêmico e 10 sujeitos saudáveis (grupo controle). Foi utilizada a cinemetria tridimensional e um sistema de análise metabólica para aquisição dos dados. Os resultados indicaram que os pacientes com AVE apresentaram Wtot e C significativamente maior em relação aos sujeitos do grupo controle. O aumento no Wtot se deve principalmente ao maior trabalho mecânico vertical (Wv) e trabalho mecânico interno (Wint), e.g., Wint rotacional do membro não acometido teve contribuição de até 50% para o resultado de Wint. Os pacientes AVE apresentaram C significativamente maior nas baixas velocidades de caminhada; enquanto nas demais velocidades os grupos foram similares. Pode-se concluir que em reposta ao prejuízo para o sistema de movimento em decorrência ao AVE, os pacientes adaptam a marcha e realizam compensações com o objetivo de minimizar os déficits funcionais.
Ischemic stroke represents 80% of stroke cases in Brazil, and it is result of a blood flow interruption into brain tissue. This upper motor neuron injury leads to hemiparesis, state characterized by partial loss of muscle strength at one side of the body. Hemiparetic gait is a common feature after stroke episode. Clinically, patients present alterations in motor control, excessive co-activation and muscle spasticity, as well as changes in passive properties of muscles. Moreover, kinematic deviations lead to a decreased range of motion and consequently a reduction in walking speed and a higher energy expenditure. Thus, a better understanding of how segmentar impairments affect total mechanical work (Wtot) and cost of transport (C) in stroke patients allows verifying the efficacy of therapeutic interventions. Therefore, this study aims to measure and compare Wtot and C at five different walking speeds between hemiparetic post-stroke patients and healthy subjects. Six patients with clinical diagnostic of ischemic stroke and ten healthy subjects (control group) participated in the present study. Three-dimensional motion analysis system and metabolic analysis system were employed for data acquisition. Results indicated that stroke group showed significantly higher Wtot and C than control group. The increased Wtot is mainly due to higher vertical mechanical work (Wv) and internal mechanical work (Wint), i.e., higher Wint rotational of uninvolved limb; accounted for a 50% contribution to Wint results. The stroke group had significantly higher C at lower speeds, while for other speeds both groups were similar. In conclusion the stroke group showed a compensatory response in the neuromuscular system, on which stroke patients adapted their gait mechanics in order to minimize functional deficits.

O objetivo do presente estudo foi comparar o comportamento dos parâmetros mecânicos (Wext, Wint, Wtot, CP, FP), parâmetros energéticos (Pmet, C, Eff, Vótima) e do mecanismo pendular (R, Rint, %Cong) durante a caminhada com carga no plano (0%), nas inclinações (+7% e +15%) e em distintas velocidades de caminhada. A amostra foi composta por 10 homens jovens, saudáveis, fisicamente ativos e não adaptados ao transporte de carga em mochilas. Os sujeitos caminharam em uma esteira rolante durante 5 min, em cinco diferentes velocidades, sem e com carga (25% da MC) transportada em mochilas, e em três planos distintos de caminhada (0%, 7% e 15%). A análise de movimento 3D (quatro câmeras de vídeo) foi realizada simultaneamente à análise de VO2. Realizaram-se rotinas computacionais para o processamento de dados cinemáticos em Matlab®. Utilizou-se ANOVA de 3 fatores para medidas repetidas, com post hoc de Bonferroni (p < 0,05; SPSS 17.0). Os resultados dos parâmetros mecânicos indicam modificações devido à velocidade e ao plano de caminhada; a carga não modificou algumas das variáveis. Todas as variáveis mecânicas aumentaram com o incremento da velocidade, o Wint e a FP diminuíram a 7% e logo aumentaram a 15%, o Wext e Wtot aumentaram com a inclinação, e o CP diminuiu com o aumento da inclinação. A carga não afetou na maioria das situações o Wext e o Wtot, demonstrando que os parâmetros mecânicos são de modo geral, independentes da carga tanto no plano como nas inclinações. As variáveis energéticas da caminhada foram influenciadas pela velocidade, inclinação e a carga. A Pmet aumentou com o incremento da velocidade, da inclinação e da carga. O C diminuiu com o incremento da velocidade e logo aumentou, atingindo um mínimo nas velocidades intermediárias e, também aumentou com o incremento da inclinação e da carga. A Eff aumentou com a velocidade, diminuiu com o aumento da inclinação e a carga. A Vótima de caminhada foi reduzida com o incremento da inclinação. Constatou-se que o mecanismo pendular é modificado principalmente como decorrência da velocidade e da inclinação do terreno, e é independente da carga. O R e o Rint aumentam com o acréscimo da velocidade de caminhada, logo diminuem com o incremento da inclinação e ambos são independentes da carga. Conclui-se que as diferentes restrições impostas através da variação da carga e inclinações provocaram adaptações na mecânica e energética da locomoção humana, sustentando a Vótima e a reconversão das energias mecânicas (R) nas inclinações. Deste modo, ainda que em menor proporção, a estratégia de minimização de energia por via pendular ainda persiste nestas condições.
The purpose of the present study was to compare the behavior of the mechanical parameters (Wext, Wint, Wtot, SF, SL), the energetic parameters (Metabolic Power, C, Eff, optimal speed) and the pendular mechanism (R, Rint, %congruity) during walking with load on level (0%) and gradients (7% and 15%) and at different walking speeds. Ten young men, healthy, physically active and not adapted to walking loaded in backpacks participated in the study. The subjects walked in a treadmill for five minutes, under five different speeds, without and with load (25% of bM) carried in backpacks and in three different gradients of walking (0%, 7% e 15%). The analysis of the 3D movement was registered (four video cameras), as well as the VO2 analysis. Computational routines for the processing of kinematic data were done in Matlab®. The results were analyzed using repeated measures ANOVA (factors: speed, gradients, load) with the Bonferroni correction for post-hoc comparisons (p < 0.05) (SPSS 17.0). The results of the mechanical parameters indicate modifications due to speed and gradients of the walking; the load did not modify some of the variables. All of the mechanical variables increased with the raise in speed, the Wint and the SF decreased at 7% and right away increased at 15%, the Wext and Wtot increased with the gradient, and the SL decreased with the raising gradient. The load did not affect most of the situations, the Wext and Wtot, decreasing with the loaded situation, showing that the mechanical parameters are, in general, independent of the load on level and gradients. The energetic parameters of the walking were influenced by the speed, the gradient and the load. The metabolic power increased with the raise in speed, in gradient and in load. The cost of transport decreased with raise in speed and increased right away, influencing the minimum cost at intermediate speeds and it also increased with the raise of the slope and the load. The efficiency increased with speed and decreased with the raise of gradient and load. The optimal speed of walking was reduced with increasing of gradient. It was verified that the pendular mechanism is mainly modified as a consequence of speed and the gradient, and is independent of load. The R and Rint increase with the raise of speed, and decrease with the raise of gradient, also there are independent of the load. The conclusion is that the different restrictions imposed through the load variation and gradients cause adaptations in the mechanics and energetic of the human locomotion, sustaining the optimal speed and reconversion of the mechanical energies in gradients. In this way, but in a smaller proportion, the strategy of minimizing the energy through the pendular mechanism still persists in these conditions.

Dois modelos mecânicos, o pêndulo-invertido e o massa-mola, explicam como os mecanismos pendular e elástico minimizam o dispêndio energético advindo dos músculos durante caminhada e corrida humana. A presente tese testa dois efeitos que, para nosso conhecimento, todavia não possuem respostas conclusivas da literatura, nomeadamente o processo de envelhecimento na mecânica da corrida humana e o efeito da inclinação do terreno na velocidade ótima da caminhada. Para estudar o primeiro efeito, as forças de reação do solo provenientes de uma plataforma de força (4m x 0,50m), foram usadas para a posterior comparação de: i) trabalho mecânico, ii) parâmetros do sistema massa-mola e, iii) assimetrias contatodespregue entre jovens e idosos. Os idosos produzem menos força durante a fase de trabalho mecânico positivo com uma menor oscilação vertical total e oscilação durante a fase aérea. Conseqüentemente a capacidade de armazenar e re-utilizar energia elástica dos tendões é prejudicada contribuindo para o maior dispêndio energético neste grupo quando comparado com jovens.Para o modelo do custo eletromiográfico (EMG) da caminhada humana criou-se duas abordagens: experimental e teórica. Em ambas as abordagens, informações da atividade EMG de dezesseis músculos, sendo 8 posturais e 8 propulsores foram coletadas e analisadas a partir da integral EMG. A abordagem teórica parece ter uma melhor relação com as evidências experimentais sobre a energética da caminhada humana em inclinações. Os principais mecanismos envolvidos na nova hipótese são i) músculos posturais que não realizam trabalho muscular, exercem uma função importante na determinação do dispêndio energético total e ii) a presente hipótese leva em consideração a co-contração de músculos antagonistas no dispêndioenergético total. Mais experimentos são necessários para confirmar o modelo apresentado neste estudo. Além disso, através de estratégias de otimização e predição linear, um modelo teórico foi delineado a fim de determinar parâmetros mecânicos (comprimento de passada e velocidade de progressão) e energéticos da locomoção terrestre em situações onde as informações disponíveis são apenas a massa e uma curva força de reação vertical versus tempo. Os resultados advindos do modelamento correspondem aos parâmetros determinados experimentalmente. Laboratórios que detenham apenas uma plataforma de força, ou nas áreas onde as informações de entrada do atual modelo sejam as únicas informações (e.g. paleontologia, biomecânica forênsica, etc), a predição de variáveis primárias da locomoção podem ser preditas com razoável acurácia.
Two mechanical models, the inverted pendulum and spring-mass, explain how do the pendular and elastic mechanisms minimizing energy expenditure from muscles during human walking and running. Here, we test two effects that, to our knowledge, do not have yet conclusive responses from literature, specifically the ageing effects on mechanics of human running, and the effect of gradient on walking optimal speed. In order to check the former effect, the ground reaction forces came from a force platform (4m x 0.5m) were used for a later comparison: i) mechanical work, ii) spring-mass parameters and, iii) landing-takeoff asymmetries. The old subjects produce less force during positive work resulting in a smaller overall and aerial vertical oscillation of the centre of mass. Consequently, the potential for restore elastic energy from tendons is reduced contributing to greater energy expenditure than in young subjects. In relation to Electromyographical (EMG) Cost of human walking we created two approaches: experimental and theoretical. In both approaches, information from EMG activity of sixteen muscles, eight postural and eight propulsor were collected and analysed. The theoretical approach seems to fit better with the energy expenditure during gradient walking. The main mechanisms involved in this new hypothesis are i) postural muscles that do not perform muscular work, play an important role in the total energy expenditure and ii) the present hypothesis take the co-contraction into account of the antagonist muscles in the total energy expenditure. Further experiments are necessary to confirm this hypothesis. Besides, using optimization and linear prediction procedures, a theoretical model was designed to estimate mechanical parameters (stride length and velocity of progression) and energetic variables of terrestrial locomotion when available information consists only of mass and one vertical ground reaction force versus time.The results from this modelling are similar to experimentally obtained data. Laboratories with just one force platform, or in areas where the present model’s input information be the unique accessible data (e.g. palaeontology, forensic biomechanics, etc) the prime variables of locomotion may be estimated with reasonable accuracy.

During, the Churchill Coalition, 1940-45, there developed within tile Government a coherent thesis that the Soviet Union would follow a post-war policy of cooperation with Britain. Soviet foreign policy-makers were perceived to have till-cc options; isolation, enmity or collaboration. Three central perceptions produced tile theory that cooperation was the likely choice. The first that developed, from 1940, was the view that Soviet aims were limited, largely defensive, and not likely to impinge upon areas of vital British interest. Far from desiring to propagwie world revolLitioii, Stalin simply wanted protection, particularly against a resurgent Germany, to continue the internal development of industrialization and state socialism interrupted by the war. After Barbarossa, the immense task of Soviet reconstruction became a second factor. Even if the USSR attempted to do this without foreign help, its rulers would seek tile cheapest possible foreign policy to enable them to coriccritratc on it: collective security in cooperation with Britain and possibly the USA. Third, Stalin was now secii iis it wise, realist statesman who had become persuaded of the wisdom of a cooperation policy will, the West. Linked with these assumptions were conclusions drawn from observations of changes in the USSR in the war, especially the revivill of nationalism, and from observation of the sensitivity of Soviet leaders. Debate on these percept ions and tile policy that should follow chiefly took place within the 1,0 departments, between thern and their ambassadors in Moscow and other places, with the military, and intermittently in Cabinet. Ilowevcr, while a policy combining "firmness" and "frankness" was preferred by most, considerations of Soviet sensitivity meant it wits never I'Llily implemented. Thus in February 1945, there was a rough consensus that [lie Soviets would try cooperation, but there was uncertainty as to the optimum British policy to maximise the chances of securing it.

La problématique du port de charges par l'Homme est l'objet de questionnements scientifiques depuis plus d'un siècle, notamment dans les armées où les soldats doivent remplir des objectifs opérationnels tout en emportant des équipements lourds, distribués de façon complexe autour de leur corps, et cela au cours d'efforts allant de quelques heures à plusieurs jours. Aussi, avec le développement des nouvelles technologies et l'arrivée des systèmes fantassins futurs sur le marché de la défense, cette problématique continue de se complexifier puisque la masse totale emportée tend encore à croître. Objectif général : Le but de ce travail de thèse était d'étudier l'impact biomécanique, métabolique et neuromusculaire du port d'un système fantassin moderne chez le soldat expérimenté. Plus précisément, une première recherche a été menée pour caractériser les effets aigus du port d'un tel équipement sur la biomécanique et le coût métabolique de la marche. Puis, une seconde recherche a été consacrée à l'étude des conséquences neuromusculaires et locomotrices d'une mission militaire (simulation sur le terrain) de durée " extrême " réalisée avec ce système fantassin moderne. Première partie : L'analyse de la marche sur tapis roulant dynamométrique a permis de montrer que le port du système fantassin en configurations de " combat " et de " marche d'approche " (principales configurations du théâtre militaire, représentant respectivement ~30 % et ~50 % de la masse corporelle des sujets) altérait le pattern spatio-temporel par rapport à la marche sans charge. Par ailleurs, le travail mécanique appliqué au centre de masse et le coût métabolique de la marche augmentaient parallèlement lors du port des deux configurations du système fantassin, ce qui résultait en un maintien du rendement locomoteur constant dans toutes les conditions testées. Le mécanisme de transfert d'énergie en pendule inversé (méthode Cavagna), permettant de minimiser les coûts mécanique et métabolique de transport, était également similaire dans toutes les conditions avec et sans charge. Enfin, bien que complexement organisés autour du corps du soldat, les équipements militaires n'induisaient pas d'effets mécaniques et métaboliques sensiblement plus importants que ceux rapportés lors du port de masses positionnées symétriquement autour de la taille ; ce mode de portage étant pourtant considéré comme l'un des plus optimisés, abstraction faite des techniques de portage sur la tête inadaptées au contexte militaire. Deuxième partie : La réalisation d'une mission simulée, incluant 21 h d'activités militaires sur le terrain et le port constant d'un système fantassin, résultait en une fatigue neuromusculaire (mesure des forces, électrostimulation et EMG) relativement modérée des muscles locomoteurs extenseurs du genou et fléchisseurs plantaires chez les soldats expérimentés inclus dans ce travail. Les origines de cette fatigue neuromusculaire étaient essentiellement périphériques, mais s'accompagnaient d'une fatigue subjective importante. Enfin, la réalisation de la mission, et donc la fatigue des muscles locomoteurs notamment associée à cette dernière, n'affectait pas sensiblement les paramètres mécaniques et métaboliques de la marche. Conclusion générale : Ce travail rapporte les premières données relatives aux effets biomécaniques, métaboliques et neuromusculaires du port d'un système fantassin moderne chez le soldat expérimenté, et ce par le biais d'une simulation opérationnelle visant à reproduire les conditions militaires

This thesis analyses the pricing and design of urban transport systems; in particular the optimal design and efficient operation of bus services and the pricing of urban transport. Five main topics are addressed: (i) the influence of considering non-motorised travel alternatives (walking and cycling) in the estimation of optimal bus fares, (ii) the choice of a fare collection system and bus boarding policy, (iii) the influence of passengers’ crowding on bus operations and optimal supply levels, (iv) the optimal investment in road infrastructure for buses, which is attached to a target bus running speed and (v) the characterisation of bus congestion and its impact on bus operation and service design. Total cost minimisation and social welfare maximisation models are developed, which are complemented by the empirical estimation of bus travel times. As bus patronage increases, it is efficient to invest money in speeding up boarding and alighting times. Once on-board cash payment has been ruled out, allowing boarding at all doors is more important as a tool to reduce both users and operator costs than technological improvements on fare collection. The consideration of crowding externalities (in respect of both seating and standing) imposes a higher optimal bus fare, and consequently, a reduction of the optimal bus subsidy. Optimal bus frequency is quite sensitive to the assumptions regarding crowding costs, impact of buses on traffic congestion and congestion level in mixed-traffic roads. The existence of a crowding externality implies that buses should have as many seats as possible, up to a minimum area that must be left free of seats. Bus congestion in the form of queuing delays behind bus stops is estimated using simulation. The delay function depends on the bus frequency, bus size, number of berths and dwell time. Therefore, models that use flow measures (including frequency only or frequency plus traffic flow) as the only explanatory variables for bus congestion are incomplete. Disregarding bus congestion in the design of the service would yield greater frequencies than optimal when congestion is noticeable, i.e. for high demand. Finally, the optimal investment in road infrastructure for buses grows with the logarithm of demand; this result depends on the existence of a positive and linear relationship between investment in infrastructure and desired running speed.

Consistently, reports in the literature have identified that a sedentary lifestyle contributes to the progression of a range of chronic degenerative diseases. The measurement of energy expenditure and physical activity pattern in children is a challenge for all professionals interested in paediatric health and from a broader perspective, the public health fraternity charged with considering longer term health consequences of physical inactivity. The primary objective of this thesis was to identify a suitable indirect and objective measurement technique for the assessment of energy expenditure and physical activity pattern in children. The ideal characteristics of such a technique are that it should be reproducible and have been validated against a criterion reference method. To achieve this goal, a series of methodological studies were undertaken (Chapters II and III). This work was essential to increase accuracy during the individualised laboratory calibration process and further minimise prediction errors when analysing data from 7 days of monitoring under free-living conditions in the second part of the study (Chapters IV and V). In the first study to verify the combined effect of body position, apparatus and distraction on children's resting metabolic rate (RMR), experiments were carried out on 14 children aged 8-12 (mean age = 10.1 years ± 1.4). Each participant underwent 2 test sessions, one week apart under three different situations: a) using mouthpiece and nose-clip (MN) or facemask (FM); b) sitting (SEAT) or lying (LY) and c) TV viewing (TV) or no TV viewing. In the first session, following 20 min rest and watching TV, the following protocol was used: LY: 20 min - stabilisation; 10 min using MN and 10 min using FM. Body position was then changed to seated: 20 min stabilisation; 10 min using FM; 10 min using MN. In the second session, FM and MN order was changed and participants did not watch TV. Data were analysed according to the eight combinations among the three studied parameters. Repeated measures ANOVA indicated statistically significant differences for &VO2 (p=0.01) and RMR (p=0.02), with TVMNSEAT showing higher values than TVFMLY. Bland-Altman analysis showed a bias for &VO2, &VCO2, RQ and RMR between TVFMLY and TVMNSEAT of -17.8±14.5 ml.min-1, -8.8±14.5 ml. min-1, 0.03±0.05 and -115.2±101.9 kcal.d-1, respectively. There were no differences in RMR measurements due to body position and apparatus when each variable was isolated. Analyses of distraction in three of four combinations indicated no difference between TV and no TV. In summary, different parameter combinations can result in increased bias and variability and thereby reported differences among children's RMR measurement. The second study dealt with treadmill adaptation and determination of self-selected (SS) walking speed. Assessment of individual and group differences in metabolic energy expenditure using oxygen uptake requires that individuals are comfortable with, and can accommodate to, the equipment being utilised. In this study, a detailed proposal for an adaptation protocol based on the SS was developed. Experiments were carried out on 27 children aged 8-12 (mean age = 10.3±1.2 yr). Results from three treadmill tests following the adaptation protocol showed similar results for step length with no significant differences among tests and lower and no statistically significant variability within- and between-days. Additionally, no statistically significant differences between SS determined over-ground and on a treadmill were verified. These results suggest that SS speed determined over-ground is reproducible on a treadmill and the 10 min familiarisation protocol based on this speed provided sufficient exposure to achieve accommodation to the treadmill. The purpose of the third study was to verify within- and between-day repeatability and variability in children's oxygen uptake ( &VO2), gross economy (GE) [ &VO2 divided by speed] and heart rate (HR) during treadmill walking based on SS. 14 children (mean age = 10.2±1.4 yr) undertook 3 testing sessions over 2 days in which four walking speeds, including SS, were tested. Within- and between-day repeatability was assessed using the Bland and Altman method and coefficients of variability (CV) were determined for each child across exercise bouts and averaged to obtain a mean group CV value for &VO2, GE and HR per speed. Repeated measures ANOVA showed no statistically significant differences in within- or between-day CV for &VO2, GE or HR at any speed. Repeatability within and between-day for &VO2, GE and HR for all speeds was verified. These results suggest that submaximal &V O2 during treadmill walking is stable and reproducible at a range of speeds based on children's SS. In the fourth study, the objective was to establish the effect of walking speed on substrate oxidation during a treadmill protocol based on SS. Experiments were carried out on 12 girls aged 8-12 (mean age = 9.9±1.4 yr). Each participant underwent 2 test sessions, one week apart. Workloads on the treadmill included 2 speeds slower than SS (1.6 [V1] and 0.8 km.h-1 [V2] slower than SS), SS (V3), and a speed 0.8 km.h-1 faster than SS (V4). Indirect calorimetry from respired gas measurements enabled total fat (FO) and carbohydrate (CHO) oxidation rates to be calculated according to the non-protein respiratory quotient (Peronnet and Massicote, 1991) and percentage of CHO and FO calculations using equations from McGilvery and Goldstein (1983). Repeated measures ANOVA followed by a Tukey Post Hoc test (p< 0.05) was used to verify differences in CHO and FO rates among speeds. Paired T-test was used to verify differences in CHO and FO rates between tests per velocity. The reliability between-day was assessed using intraclass correlation coefficient (ICC). Results showed significant differences for CHO among all speeds, as well as significant differences for FO between V1 and V2 against V3 and V4 in both tests. Analyses between trials per velocity showed no significant substrate use differences as well as acceptable reliability. At the self-selected speed (V3) there was an accentuation in FO reduction as well as an increase in CHO oxidation. The purpose of the fifth study was to determine whether there were differences in substrate oxidation between girls (G) and women (W) during a treadmill protocol based on SS. Experiments were carried out on 12 G aged 8-12 (mean age = 9.9±1.4 yr) and 12 W aged 25-38 (mean age = 32.3±3.8 yr). The treadmill protocol included 6 min workloads followed by 5 min rest periods. Workloads included 2 speeds slower than SS (1.6 (V1) and 0.8 km.h-1 (V2) slower than SS), SS (V3), and a speed 0.8 km.h-1 faster than SS (V4). Total fat and carbohydrate (CHO) oxidation rates were calculated from indirect calorimetry according to the non-protein respiratory quotient. Repeated measures ANOVA followed by a Tukey Post Hoc test was used to verify intra-test differences in CHO and fat oxidation rates among speeds. Intergroup differences were analysed using paired T-test. Fat utilisation in W achieved a plateau at a relative velocity 0.8 km.h-1 slower than SS, but for G, fat utilisation increased until SS, and then stabilised upon reaching the higher velocity. CHO oxidation curves rose abruptly above V2 for W, while for G the acute increase occurred after SS (V3). Collectively, these results indicate that as walking intensity increases G are able to meet the energy demands of the work by increasing fat oxidation together with the increased CHO oxidation up to SS. In contrast for W, increasing CHO oxidation is associated with an early decrease in fat utilisation at a velocity slower than the self-selected speed. The sixth study dealt with validation of indirect techniques for the measurement of energy expenditure in free-living conditions against the DLW technique. Experiments were carried out on 19 children aged 8-12 (mean age = 10.3±1.0 yr). To indirectly predict energy expenditure 12 different procedures were used. Only one procedure, combining activity and heart rate (AHbranched), was based on a group equation, the others were based on individualised regression. Three of the individually-based techniques were able to accurately predict energy expenditure in free-living conditions. These tecniques were HRPAnetRMR using HRnet [HR exercise minus sleep HR (SHR)] against PAnet (measured PA exercise minus measured RMR) and upper and lower body equations corrected by RMR; HRPAnet4act using the same procedure but corrected by the mean resting &VO2 for 4 resting activities [(4act) = supine watching TV, sitting watching TV, sitting playing computer games and standing], and HRPALBnet4act using only lower body activities and corrected by 4act. HRPAnetRMR was only slightly more accurate than HRPAnet4act and HRPALBnet4act, but this technique is only adjusted by RMR whereas the other two are heavily dependent on more complex laboratory calibration. Bland and Altman (1986) analyses showed no significant differences between AHbranched predicted and measured TEE using the DLW technique. A SEE of 79 kcal.d-1 and a mean difference of 72 kcal.d-1, with a 95% CI ranging from -238 to 93.9 kcal.d-1 was found. In addition, no significant differences between predicted HRPAnetRMR and measured TEE using DLW were found, showing an SEE of 99 kcal.d-1 and a mean difference of -67 kcal.d-1, and a 95% CI ranging from -276.6 to 141.9 kcal.d-1. AHbranched and HRPAnetRMR were both valid and similarly suitable for the prediction of energy expenditure in children under free-living conditions. Significant associations between DLWAEE and the after-school time window indicated that this time window as an important discretionary period representative of children physical activity. However, the duration of the after-school time windows should be more carefully considered. Accelerometer data showed a better association between the largest after-school time window (3.5 hr) and measured TEE. The final study, completed with 19 children aged 8-12 (10.3±1.0 yr) highlighted, under laboratory conditions across a range of walking and running speeds, the inadequacy of the use of the standard MET in children. This traditional approach overestimates energy expenditure with an increased difference linearly related to speed increments. Minute-by-minute analyses of 7 days of free-living monitoring showed an average overestimation of 64 minutes per day for moderate-to-vigorousphysical- activity (MVPA) using the standard MET compared with the individually measured MET. For all intensities, these differences were statistically significant (p< 0.001). The second part of this study showed a variability of 20% in the average time spent at MVPA when comparing HR I 140 bpm and HR > 50%P &VO2 (P &VO2 = the highest &VO2 observed during an exercise test to exhaustion). Results of the current study compared to observations in the literature showed that HR I 140 bpm consistently estimates lower MVPA time than HR > 50%P &VO2. When these two PA indices were compared with individual and standard MET measured minute-byminute, statistically significant differences were verified among all of them at MPA, but no differences were verified at VPA, except between individual and standard METs. However, whether each one of the PA indices used are under- or overestimating time at MVPA is still debatable due to the lack of a gold standard. Finally, each index used in this study classified different numbers of participants as achieving the PA target of 60 min.d-1. The wide variability between indices when attempting to classify children who are achieving the recommended target is cause for great concern because habitually these indices are utilised as screening tools in paediatric and public health settings and used to guide behavioural interventions.

Consistently, reports in the literature have identified that a sedentary lifestyle contributes to the progression of a range of chronic degenerative diseases. The measurement of energy expenditure and physical activity pattern in children is a challenge for all professionals interested in paediatric health and from a broader perspective, the public health fraternity charged with considering longer term health consequences of physical inactivity. The primary objective of this thesis was to identify a suitable indirect and objective measurement technique for the assessment of energy expenditure and physical activity pattern in children. The ideal characteristics of such a technique are that it should be reproducible and have been validated against a criterion reference method. To achieve this goal, a series of methodological studies were undertaken (Chapters II and III). This work was essential to increase accuracy during the individualised laboratory calibration process and further minimise prediction errors when analysing data from 7 days of monitoring under free-living conditions in the second part of the study (Chapters IV and V). In the first study to verify the combined effect of body position, apparatus and distraction on children's resting metabolic rate (RMR), experiments were carried out on 14 children aged 8-12 (mean age = 10.1 years ± 1.4). Each participant underwent 2 test sessions, one week apart under three different situations: a) using mouthpiece and nose-clip (MN) or facemask (FM); b) sitting (SEAT) or lying (LY) and c) TV viewing (TV) or no TV viewing. In the first session, following 20 min rest and watching TV, the following protocol was used: LY: 20 min - stabilisation; 10 min using MN and 10 min using FM. Body position was then changed to seated: 20 min stabilisation; 10 min using FM; 10 min using MN. In the second session, FM and MN order was changed and participants did not watch TV. Data were analysed according to the eight combinations among the three studied parameters. Repeated measures ANOVA indicated statistically significant differences for &VO2 (p=0.01) and RMR (p=0.02), with TVMNSEAT showing higher values than TVFMLY. Bland-Altman analysis showed a bias for &VO2, &VCO2, RQ and RMR between TVFMLY and TVMNSEAT of -17.8±14.5 ml.min-1, -8.8±14.5 ml. min-1, 0.03±0.05 and -115.2±101.9 kcal.d-1, respectively. There were no differences in RMR measurements due to body position and apparatus when each variable was isolated. Analyses of distraction in three of four combinations indicated no difference between TV and no TV. In summary, different parameter combinations can result in increased bias and variability and thereby reported differences among children's RMR measurement. The second study dealt with treadmill adaptation and determination of self-selected (SS) walking speed. Assessment of individual and group differences in metabolic energy expenditure using oxygen uptake requires that individuals are comfortable with, and can accommodate to, the equipment being utilised. In this study, a detailed proposal for an adaptation protocol based on the SS was developed. Experiments were carried out on 27 children aged 8-12 (mean age = 10.3±1.2 yr). Results from three treadmill tests following the adaptation protocol showed similar results for step length with no significant differences among tests and lower and no statistically significant variability within- and between-days. Additionally, no statistically significant differences between SS determined over-ground and on a treadmill were verified. These results suggest that SS speed determined over-ground is reproducible on a treadmill and the 10 min familiarisation protocol based on this speed provided sufficient exposure to achieve accommodation to the treadmill. The purpose of the third study was to verify within- and between-day repeatability and variability in children's oxygen uptake ( &VO2), gross economy (GE) [ &VO2 divided by speed] and heart rate (HR) during treadmill walking based on SS. 14 children (mean age = 10.2±1.4 yr) undertook 3 testing sessions over 2 days in which four walking speeds, including SS, were tested. Within- and between-day repeatability was assessed using the Bland and Altman method and coefficients of variability (CV) were determined for each child across exercise bouts and averaged to obtain a mean group CV value for &VO2, GE and HR per speed. Repeated measures ANOVA showed no statistically significant differences in within- or between-day CV for &VO2, GE or HR at any speed. Repeatability within and between-day for &VO2, GE and HR for all speeds was verified. These results suggest that submaximal &V O2 during treadmill walking is stable and reproducible at a range of speeds based on children's SS. In the fourth study, the objective was to establish the effect of walking speed on substrate oxidation during a treadmill protocol based on SS. Experiments were carried out on 12 girls aged 8-12 (mean age = 9.9±1.4 yr). Each participant underwent 2 test sessions, one week apart. Workloads on the treadmill included 2 speeds slower than SS (1.6 [V1] and 0.8 km.h-1 [V2] slower than SS), SS (V3), and a speed 0.8 km.h-1 faster than SS (V4). Indirect calorimetry from respired gas measurements enabled total fat (FO) and carbohydrate (CHO) oxidation rates to be calculated according to the non-protein respiratory quotient (Peronnet and Massicote, 1991) and percentage of CHO and FO calculations using equations from McGilvery and Goldstein (1983). Repeated measures ANOVA followed by a Tukey Post Hoc test (p< 0.05) was used to verify differences in CHO and FO rates among speeds. Paired T-test was used to verify differences in CHO and FO rates between tests per velocity. The reliability between-day was assessed using intraclass correlation coefficient (ICC). Results showed significant differences for CHO among all speeds, as well as significant differences for FO between V1 and V2 against V3 and V4 in both tests. Analyses between trials per velocity showed no significant substrate use differences as well as acceptable reliability. At the self-selected speed (V3) there was an accentuation in FO reduction as well as an increase in CHO oxidation. The purpose of the fifth study was to determine whether there were differences in substrate oxidation between girls (G) and women (W) during a treadmill protocol based on SS. Experiments were carried out on 12 G aged 8-12 (mean age = 9.9±1.4 yr) and 12 W aged 25-38 (mean age = 32.3±3.8 yr). The treadmill protocol included 6 min workloads followed by 5 min rest periods. Workloads included 2 speeds slower than SS (1.6 (V1) and 0.8 km.h-1 (V2) slower than SS), SS (V3), and a speed 0.8 km.h-1 faster than SS (V4). Total fat and carbohydrate (CHO) oxidation rates were calculated from indirect calorimetry according to the non-protein respiratory quotient. Repeated measures ANOVA followed by a Tukey Post Hoc test was used to verify intra-test differences in CHO and fat oxidation rates among speeds. Intergroup differences were analysed using paired T-test. Fat utilisation in W achieved a plateau at a relative velocity 0.8 km.h-1 slower than SS, but for G, fat utilisation increased until SS, and then stabilised upon reaching the higher velocity. CHO oxidation curves rose abruptly above V2 for W, while for G the acute increase occurred after SS (V3). Collectively, these results indicate that as walking intensity increases G are able to meet the energy demands of the work by increasing fat oxidation together with the increased CHO oxidation up to SS. In contrast for W, increasing CHO oxidation is associated with an early decrease in fat utilisation at a velocity slower than the self-selected speed. The sixth study dealt with validation of indirect techniques for the measurement of energy expenditure in free-living conditions against the DLW technique. Experiments were carried out on 19 children aged 8-12 (mean age = 10.3±1.0 yr). To indirectly predict energy expenditure 12 different procedures were used. Only one procedure, combining activity and heart rate (AHbranched), was based on a group equation, the others were based on individualised regression. Three of the individually-based techniques were able to accurately predict energy expenditure in free-living conditions. These tecniques were HRPAnetRMR using HRnet [HR exercise minus sleep HR (SHR)] against PAnet (measured PA exercise minus measured RMR) and upper and lower body equations corrected by RMR; HRPAnet4act using the same procedure but corrected by the mean resting &VO2 for 4 resting activities [(4act) = supine watching TV, sitting watching TV, sitting playing computer games and standing], and HRPALBnet4act using only lower body activities and corrected by 4act. HRPAnetRMR was only slightly more accurate than HRPAnet4act and HRPALBnet4act, but this technique is only adjusted by RMR whereas the other two are heavily dependent on more complex laboratory calibration. Bland and Altman (1986) analyses showed no significant differences between AHbranched predicted and measured TEE using the DLW technique. A SEE of 79 kcal.d-1 and a mean difference of 72 kcal.d-1, with a 95% CI ranging from -238 to 93.9 kcal.d-1 was found. In addition, no significant differences between predicted HRPAnetRMR and measured TEE using DLW were found, showing an SEE of 99 kcal.d-1 and a mean difference of -67 kcal.d-1, and a 95% CI ranging from -276.6 to 141.9 kcal.d-1. AHbranched and HRPAnetRMR were both valid and similarly suitable for the prediction of energy expenditure in children under free-living conditions. Significant associations between DLWAEE and the after-school time window indicated that this time window as an important discretionary period representative of children physical activity. However, the duration of the after-school time windows should be more carefully considered. Accelerometer data showed a better association between the largest after-school time window (3.5 hr) and measured TEE. The final study, completed with 19 children aged 8-12 (10.3±1.0 yr) highlighted, under laboratory conditions across a range of walking and running speeds, the inadequacy of the use of the standard MET in children. This traditional approach overestimates energy expenditure with an increased difference linearly related to speed increments. Minute-by-minute analyses of 7 days of free-living monitoring showed an average overestimation of 64 minutes per day for moderate-to-vigorousphysical- activity (MVPA) using the standard MET compared with the individually measured MET. For all intensities, these differences were statistically significant (p< 0.001). The second part of this study showed a variability of 20% in the average time spent at MVPA when comparing HR I 140 bpm and HR > 50%P &VO2 (P &VO2 = the highest &VO2 observed during an exercise test to exhaustion). Results of the current study compared to observations in the literature showed that HR I 140 bpm consistently estimates lower MVPA time than HR > 50%P &VO2. When these two PA indices were compared with individual and standard MET measured minute-byminute, statistically significant differences were verified among all of them at MPA, but no differences were verified at VPA, except between individual and standard METs. However, whether each one of the PA indices used are under- or overestimating time at MVPA is still debatable due to the lack of a gold standard. Finally, each index used in this study classified different numbers of participants as achieving the PA target of 60 min.d-1. The wide variability between indices when attempting to classify children who are achieving the recommended target is cause for great concern because habitually these indices are utilised as screening tools in paediatric and public health settings and used to guide behavioural interventions.

碩士
國立臺灣大學
醫學工程學研究所
101
Background: While metabolic energy cost ambulation has been extensively investigated, mechanical energy cost is relatively unexplored which will be discussed . There were evidences to show that under the same walking speed the older consume higher metabolic energy than the younger. Research literatures also support that the self-selected walking speeds are not much different between the two groups but the cadence of the elders is higher. Furthermore, the aged group showed a redistribution of joint torques and powers during gaits. Purpose: The study is designed to answer the prominent research question: Would the redistribution of joint powers in elders change the segmental energy distribution and cause the high mechanical energy cost during level walking and how? Energy flow analysis would be conducted to look into biomechanical reasons that cause higher energy cost in elders. Materials and Methods : 15 male young (24.2 ± 0.77yrs) and 15 male older adults(71 ± 3.46yrs) participated in the study. Their anthropometric characteristics were: Young: Height (1.76 ± 0.02m), Mass (70 ± 9.37kg), BMI (22 ± 2.92). Elders: Height (1.64 ± 0.01m), Mass (65 ± 3.76kg), BMI (24 ± 1.28). All subjects walked along a 10-meter walkway with shoes at slower speed, self-selected speed and faster speed, respectively. There were 24 segmental landmarks tracked at 100 Hz by two optoelectric sensors (Optotrak Certus, Northern Digital Inc., Waterloo, Canada) for capturing body motions. The kinetic data will be synchronously collected via three force platforms (Accugait, Advanced Mechanical Technology Inc., Massachusetts, USA) embedded in the walkway. Each subject completed at least three successful gait trails after 3-minute practice. Results: For walking speed, it is not significantly different between young men group and elders group. However, a t-test analysis indicated a significant difference between the means of mechanical energy cost of the two groups. We focus on second double limb support(50%-62%), initial swing(62%-75), mid swing(75%-85%), and terminal swing(85%-100%). An independent t-test was conducted evaluated the means of potential and kinetic energy of the two groups. Especially during fast walking, the walking speed is not significantly different, and the segmental kinetic energy is also not significantly different. In analyzing the energy rate of segments and joints by discussing linear and angular flow individually. For linear energy flow of joints, the linear energy rate for proximal and distal are almost symmetrical to the x-axis, it means that the energy rate of the opposite ends of hip joint are with the same value but different signs. The physical meaning is that the linear energy flow is through the joint, but it does not appear on the overall joint power. Conclusions: The cost for fast walking is pretty higher in elders compared to it of young men. A partial explanation for this may lie in the fact that during walking, elders could not store energy effectively, so they change their strategy of walking and joints should generate additional power, and cause higher mechanical energy cost.

abstract: The effects of aging on muscular efficiency are controversial. Proponents for increased efficiency suggest that age-related changes in muscle enhance efficiency in senescence. Exercise study results are mixed due to varying modalities, ages, and efficiency calculations. The present study attempted to address oxygen uptake, caloric expenditure, walking economy, and gross/net cycling efficiency in young (18-59 years old) and older (60-81 years old) adults (N=444). Walking was performed at three miles per hour by 86 young (mean = 29.60, standard deviation (SD) = 10.50 years old) and 121 older adults (mean = 66.80, SD = 4.50 years old). Cycling at 50 watts (60-70 revolutions per minute) was performed by 116 young (mean= 29.00, SD= 10.00 years old) and 121 older adults (m = 67.10 SD = 4.50 years old). Steady-state sub-maximal gross/net oxygen uptake and caloric expenditures from each activity and rest were analyzed. Net walking economy was represented by net caloric expenditure (kilocalories/kilogram/min). Cycling measures included percent gross/net cycling efficiency (kilo-calorie derived). Linear regressions were used to assess each measure as a function of age. Differences in age group means were assessed using independent t-tests for each modality (alpha = 0.05). No significant differences in mean oxygen uptake nor walking economy were found between young and older walkers (p>0.05). Older adults performing cycle ergometry demonstrated lower gross/net oxygen uptakes and lower gross caloric expenditures (p< 0.05).
Dissertation/Thesis
Masters Thesis Exercise and Wellness 2014

The strength of time-dependent correlations known as stride interval (SI) dynamics have been proposed as an indicator of neurologically healthy gait. Most recently, it has been hypothesized that these dynamics may be necessary for gait efficiency although the supporting evidence to date is limited. To gain a better understanding of this relationship, this study investigated stride interval dynamics, the energy cost of walking, and physical activity in a pediatric population. The findings indicate that differences in energy cost are not reflected in the stride interval dynamics of able-bodied children. Interestingly, increasing physical activity levels were associated with decreasing variance in stride interval dynamics between subjects, though this finding only approached significance (p=0.054). Lastly, this study found that stride interval dynamics in children as young as nine years were comparable to stride interval dynamics found in healthy young adults.

Unilateral, below-knee amputees have altered gait mechanics, which can significantly affect mobility. For example, amputees often have asymmetric leg loading as well as higher metabolic cost and an increased risk of falling compared to non-amputees. Below-knee amputees lose the functional use of the ankle muscles, which are critical in non-amputee walking for providing body support, forward propulsion and leg-swing initiation. The ankle muscles also regulate angular momentum in non-amputees, which is important for providing body stability and preventing falls. Thus, compensatory mechanisms in amputee walking are developed to accomplish the functional tasks normally provided by the ankle muscles. In Chapters 2 and 3, three-dimensional forward dynamics simulations of amputee and non-amputee walking were generated to identify compensatory mechanisms and their effects on joint loading and metabolic cost. Results showed that the prosthesis provided body support, but did not provide sufficient body propulsion or leg-swing initiation. As a result, compensations by the residual leg gluteus maximus, gluteus medius, and hamstrings were needed. The simulations also showed the intact leg tibio-femoral joint contact impulse was greater than the residual leg and that the vasti and hamstrings were the primary contributors to the joint impulse on both the intact and residual legs. The amputee simulation had higher metabolic cost than the non-amputee simulation, which was primarily due to prolonged muscle activity from the residual leg gluteus maximus, gluteus medius, hamstrings, vasti and intact leg vasti and ankle muscles. In Chapter 4, whole-body angular momentum in amputees and non-amputees was analyzed. Reduced residual leg propulsion resulted in a smaller range of sagittal plane angular momentum in the second half of the gait cycle. Thus, to conserve angular momentum, reduced braking was needed in the first half of the gait cycle. Decreased residual leg braking appears to be an important mechanism to regulate sagittal plane angular momentum in amputee walking, but was also associated with a greater range of angular momentum that may contribute to reduced stability in amputees. These studies have provided important insight into compensatory mechanisms in below-knee amputee walking and have the potential to guide rehabilitation methods to improve amputee mobility.
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Introduzione. L’ictus cerebrale rappresenta la prima causa di morte e disabilità. La fitness cardiovascolare (VO2peak) nell’ictus è ridotta del 50% rispetto a soggetti sani. Studi recenti hanno dimostrato i benefici dell’allenamento in tale popolazione. Obiettivi dello studio. Il primo obiettivo dello studio è di analizzare gli effetti di un allenamento ad alta intensità (treadmill o rinforzo muscolare massimale ) nel migliorare le capacità deambulatorie, la forza muscolare, la qualità della vita e la fitness cardiovascolare. Il secondo obiettivo è di indagare le modificazioni circolatorie periferiche all’arto inferiore a seguito di tale tipologia di allenamento. Il terzo obiettivo è di confrontare le due tipologie di allenamento. Materiali e metodi. Soggetti affetti da ictus cerebrale in fase cronica sono stati arruolatati e rispettivamente sottoposti ad un allenamento ad alta intensità della forza o rinforzo muscolare massimale. Nella fase di arruolamento i soggetti sono stati screnati attraverso ECG a riposo e sottosforzo. Prima dell’inizio dell’allenamento e alla fine, i soggetti sono stati sottoposti a test clinici (6MWT, 10MWT, SF-36, SIS) e strumentali (Gait analysis, V02peak, Cw, Peripheral Factors). Risultati. Quindici soggetti sono stati arruolati nello studio. A seguito dell’allenamento ad alta intensità su treadmill, i soggetti hanno riportato miglioramenti significativi nella resistenza (p=0.012), e velocità del cammino (p=0.042), parametri spazio-temporale del cammino (stride length p=0.011, step length paretic side p=0.012, cadence p=0.037 and symmetry ratio p=0.012),, fitness cardiovascolare (relative VO2peak p=0.025, absolute VO2peak p=0.025) e costo del cammino (100% of self-selected speed (p=0.018)). Inoltre, si sono riscontrate modificazioni circolatorie periferiche soprattutto all’arto inferiore plegico (non-paretic lower limb HBO p=0.012, paretic lower limb HBO p=0.018 and HB p=0.017). I soggetti sottoposti ad un rinforzo muscolare massimale, hanno riportato miglioramenti significativi nella forza in entrambi gli arti inferiori (non-paretic lower limb isometric extension p=0.018 and flexion p=0.018, paretic lower limb isometric extension p=0.018 and flexion p=0.034). L’allenamento ad alta intensità su treadmill risulta essere maggiormente efficace rispetto all’allenamento rinforzo muscolare massimale nel migliorare le capacità deambulatorie, la fitness cardiovascolare e il costo del cammino. Conclusioni. L’allenamento ad alta intensità su treadmill migliora le capacità deambulatorie, la fitness cardiovascolare e riduce il costo del cammino. Inoltre, tale allenamento porta a modificazioni circolatorie periferiche soprattutto all’arto inferiore plegico.
Introduction. Stroke is a major cause of death and long-term disability across the globe. Physical fitness is impaired after stroke. Cardiorespiratory fitness (VO2peak) is roughly 50% of that in healthy people of the same age and sex. Previous studies have demonstrated the trainability of stroke survivors and documented beneficial physiological, psychological, sensorimotor, strength, endurance, and functional effects of various types of exercises. Aims of the study. The first aim of this project was to investigate the effects of a high intensitive physical training (high intensity treadmill training and maximal strength training) in improving gait ability, muscle strength, quality of life and cardiorespiratory fitness in cerebral stroke subjects in chronic phase. The second aim was to understand the mechanism of peripheral circulatory adaptations on lower limb muscles after high intensitive physical training. The third was to compare the effects of two type of training in such population. Material and Methods. Subjects suffered from cerebral stroke in chronic phase were enrolled in this study and respectively allocated in the high intensity treadmill training group and maximal strength training group. Subjects performed 3-month training, 3 times per week (Monday-Wednesday-Friday). The subject were screened by a medical assessment consisting of resting electrocardiography (ECG) and rest ECG pre-training and post training. Subjects were evaluated by mean clinical (6MWT, 10MWT, SF-36, SIS) and instrumental test (Gait analysis, V02peak, Cw, Peripheral Factors). Results. Fifteen subjects were enrolled in the study. Three months of high intensity treadmill training increased gait resistance (p=0.012), gait speed (p=0.042), spatio-temporal gait analysis (stride length p=0.011, step length paretic side p=0.012, cadence p=0.037 and symmetry ratio p=0.012), enhanced VO2peak (relative VO2peak p=0.025, absolute VO2peak p=0.025) and reduced cost of walking at 100% of self-selected speed (p=0.018). Furthermore, peripheral circulation adaptations were funded, in particular in paretic lower limb muscle (non-paretic lower limb HBO p=0.012, paretic lower limb HBO p=0.018 and HB p=0.017). On the other hand, patient underwent maximal strength training increased lower-limb strength (non-paretic lower limb isometric extension p=0.018 and flexion p=0.018, paretic lower limb isometric extension p=0.018 and flexion p=0.034) with no improvements in gait ability and cardiorespiratory fitness. High intensity treadmill training resulted more effective than maximal strength training in improving gait ability and cardiorespiratory fitness and reducing cost of walking. Conclusion. High intensity treadmill training improves gait ability, enhanced VO2peak and reduced cost of walking. Furthermore, peripheral circulation adaptations were funded, in particular in paretic lower limb muscle. Subjects underwent maximal strength training improved muscle strength in both lower limbs’ muscles, with no increased in gait ability and aerobic capacity.

Background: Though numerous studies have compared overground and treadmill walking there still exists a significant debate about whether the two modes of walking are equivalent. The present study provides a comprehensive evaluation of overground and treadmill walking at matched speeds and increasing treadmill speeds. Walking performance was compared in healthy adults, in people with stroke and between the groups. This is important to know because any differences may have implications for gait training in both groups. Methods: Ten healthy adults (50-73 years) and ten subjects with stroke (54-80 years) walked at their self-selected speed overground which was matched on a treadmill. Temporal parameters, angular kinematics and vertical ground reaction forces were recorded during walking once subjects were in steady state as determined from their heart rate and oxygen uptake, both of which were also recorded. Belt speed was then increased 10% and 20% above matched speed and steady state recordings obtained. Speed related adjustments were also evaluated and compared between the two groups of subjects. Results: For healthy adults, step, stride, and joint angular kinematics were similar for both modes of walking. Small reductions in double support time and decreased push-off force were evident on the treadmill. For subjects with stroke, step, stride, and stance times were longer when walking overground but the degree of symmetry was comparable for both surfaces. Kinematic data revealed interlimb asymmetry was more pronounced for all lower limb joint excursions during overground walking and vertical forces were higher. In comparison to healthy adults, stroke subjects walked with lower cadence, shorter strides, lower stance time, and smaller lower limb joint excursions than their healthy counterparts. When compared with overground walking the metabolic requirements of treadmill walking for healthy adults and subjects with stroke however were about higher by 23% and 15% respectively. All temporal-distance parameters, hip joint excursion, F1 and F2 forces and metabolic costs showed main effects of speed. An interaction between speed and group indicated that oxygen consumption increased at a greater rate in stroke than healthy subjects. Conclusions: The findings suggest that, although overground and treadmill gait patterns are similar for each group of subjects, people with stroke adopt a more symmetrical kinematic walking pattern on the treadmill that is maintained at faster belt speeds. Although there are differences in gait patterns between healthy and stroke subjects, both groups respond to the challenge of increased walking speed in the same way. One important difference is the abnormal elevation of energy demands associated with treadmill walking at faster speeds in stroke. Clinically, this warrants consideration as it may lead to premature fatigue and undesirable cardiorespiratory challenge in this group of individuals.
Thesis (Ph.D, Rehabilitation Science) -- Queen's University, 2009-08-27 06:41:19.999