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Falls are a health care problem for lower limb prosthetic users. The study of gait stability in lower limb prosthetic users facilitates improved insight and knowledge in different adaptation strategies of the human body in order to walk as functionally as possible with a prosthesis. The aim of this thesis was to determine how prosthetic users cope with unbalanced situations during walking and how these coping strategies may differ from able-bodied individuals. Improved understanding of such mechanisms may help reduce fall incidence. A number of prosthetic factors were considered including the use of a prosthetic foot incorporating an ankle joint, compared to a conventional prosthetic foot. Additionally, the effect of different alignments and the aetiology of the amputation or absence (congenital vs acquired amputation) was also considered. The study was conducted using an advanced dual-belt instrumented treadmill (CAREN). The protocol of perturbations in the study was adopted from a previous work by a group of researchers in University of Strathclyde (Roeles et al., 2018). Interventions used were anteroposterior (AP) perturbations by means of sudden changes in the walking speed to mimic a slip that can be faced in real-life situations. Main Outcome Measurements measured were AP and ML margins of stability (MoS) Hof et al. (2005). Step length, width and time were also measured to investigate the coping strategy following perturbation. Prosthetic users were less stable than able-bodied individuals. The involvement of the prosthetic side to recover stability was limited therefore, during rehabilitation stability training tasks for the intact side may help the prosthetic users enhance their overall stability and may reduce the fall incidence rate. Energy storing and return prosthetic feet may provide a sufficient level of stability compared to the feet which incorporate a moving ankle mechanism. The Ossur Pro-Flex foot demonstrated enhanced stability in the AP direction. Alignment changes from the optimal alignment may impose extra challenge to the stability. A short prosthesis was found to be the most challenging alignment change in response to perturbation. The prosthetic user with congenital related limb anomaly was found to be more stable than the prosthetic users with other lower limb loss. The outcomes of this study are novel and have potential to improve the understanding of how prosthetic users (acquired and congenital) react in when stability is compromised and the variables which may affect this further (foot design and alignment). It is envisaged that greater understanding of different adaptation strategies of the human body may help influence future prosthetic treatment, prescription, alignment and potentially component design.

This thesis presents the development of a sensor based on the pyroelectric and piezoelectric effects that can be used to measure both temperature and/or axial stress for specific use within a prosthetic socket, and more generally as a responsive temperature sensor capable of detecting high frequency skin temperature oscillations in medical diagnostic applications. Knowledge of an amputees’ residual limb skin temperature is considered to be of particular importance as an indicator of tissue health. With this in mind, a prototype wearable sensor for real-time temperature measurement at the skin/prosthetic socket/liner interface was developed and measurements that provide a proof of concept are presented. The sensor exploits the large pyroelectric effect present in ferroelectric lead zirconate titanate PbZrx(Ti(1-x)03) (PZT) and has several inherent advantages over other methods of temperature sensing. The sensor element chosen is a low cost commercially available diaphragm PZT-5H element with a brass substrate. While the development of the sensor concentrates on the specific application of surface temperature measurement, the mathematical models developed also describe the sensor response to an applied axial stress that can be used as a measure of the pressure applied to the residual limb by the confinement of a prosthetic socket. Using the mathematical models, substrate clamping was found to significantly increase the effective pyroelectric coefficient. A subsequent experimentally obtained value for the effective pyroelectric coefficient was found to be very close to the value predicted by the mathematical models, confirming the effect of substrate clamping. Immittance models are developed to investigate the temperature dependence of the sensor element immittance, mechanical and constant strain electrical capacitances over the temperature range 20°C to 40°C. Both capacitances were found to be significantly temperature dependent and therefore charge-mode signal conditioning was chosen to mitigate temperature effects on the signal-conditioning response. Subsequent response measurements were found to yield a linear response over the temperature range of interest. Bipolar and unipolar charge amplifier designs are developed and built to provide signal-conditioning for use in sensor response measurements. The unipolar type is a single supply 5V prototype with low power consumption and is also designed for use with an e-Health platform in a wearable sensor configuration. In addition, a single supply enhanced open loop gain design that mitigates the effect of reduced dielectric resistance in the sensor element is presented. Using the developed mathematical models, the sensor is predicted to be capable of measuring frequencies from DC up to 6.8rads−1 with a rise time to the 98% peak of 0.12s and 0.18s for a DC and 6.8rads−1 step, respectively. However, the use of a polymer liner between the sensor element and measurement surface is found to severely limit the usable frequency response of the sensor due to severe amplitude and phase distortion, precluding direct use of the sensor to measure skin surface temperature. Being relevant to the safety of remote e-Health monitoring, the challenges ICT networks must face to maintain quality of service are discussed and it is shown that an increasing amount of traffic, increasing power consumption and electronic bottlenecks are three main challenges that require a solution. The ability of ICT networks to satisfy the growing global demand for data is under threat due to the speed limitations of current CMOS based electronic technologies, leading to electronic bottlenecks and threats to the sustainability of the quality of service critically required for e-Health monitoring.

Strong evidence exists to support participation in physical activity to maintain and improve health in general and clinical populations. However, little is known about the physical behaviours of adults with lower limb absence. This thesis makes four original contributions to knowledge. The first contribution is a systematic review conducted to explore the motivations and barriers to participation in physical activity, exercise and sports in people with lower limb absence. Findings show that adults with lower limb absence are not participating in physical activity conducive to health benefits. Post-amputation levels of participation are lower than pre-amputation levels, and more barriers than motivations exist to participation. The second contribution is the exploration of healthcare professionals' awareness and understanding of physical activity guidelines and how physical activity is promoted in clinical settings. Results from an online survey designed for United Kingdom healthcare professionals show that this group has awareness and knowledge of physical activity guidelines. With appropriate support and resources prosthetic healthcare professionals can be encouraged to incorporate physical activity promotion into routine clinical practice. The third contribution is the examination of reliability and validity of an accelerometer when worn by adults with lower limb absence. The activPAL accelerometer is a reliable and valid measurement tool in adults with lower limb absence when used in a laboratory setting, and placement of the monitor on the sound side limb is recommended for testing. The fourth contribution is the findings from a free-living study of physical behaviour in adults with lower limb absence who are shown to be physically active daily but could be encouraged to be more active and less sedentary. Data were also matched on gender, age and employment status to that of a non-clinical control group where it was shown those with limb absence are less active than healthy individuals.

Ankle-foot orthoses are commonly prescribed amongst subjects with diplegic cerebral palsy as a conservative orthotic intervention. Multi-articular and bi-articular muscles are more severely involved in subjects with diplegic cerebral palsy. Appropriate clinical assessment including assessment of these muscles enables optimum ankle-foot orthosis footwear combination (AFO-FC) prescription and any required adjunct therapy. The overarching aim of this thesis was to investigate the effect of optimisation of the temporal midstance shank kinematics with the use of an AFO- FC on several variables including shank kinematics, thigh kinematics, vertical component of ground reaction force (FZ2) and ground reaction force (GRF) alignment in relation to hip and knee joint in temporal midstance to late stance. The understanding of the implication of, and the tools used to conduct assessment procedures and measurement processes were tested in the assessment of bi-articular muscles (specifically rectus femoris), to ascertain if results were predictive of presenting gait deviations and hence provide information to optimise treatment. The results of initial study suggested that a positive influence on the shank kinematics, thigh kinematics, FZ2 and GRF alignment in relation to hip and knee joint in temporal midstance to late stance was observed with the use of an AFO-FC. The results of a further study illustrated that a dominance relationship of the catch angle/length of rectus femoris (RF) measured using the Duncan-Ely with the knee or the hip joints varies at different gait points/periods. Additionally, the effect of dynamic shortness of4the RF differed on gait from the effect of true shortness. The results of series of studies testing the feasibility of using a 2-dimensional analysis system (PnO Clinical Movement Data) for hip, knee and ankle sagittal plane passive joint range of motion measurement during physical assessment confirmed the reliability and accuracy of this system.