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This paper describes the design and evaluation of a miniature kinematic sensor based three dimensional (3D) joint angle measurement technique. The technique uses a combination of rate gyroscope, accelerometer and magnetometer sensor signals. The technique enables 3D inter-segment joint angle measurement and could be of benefit in a variety of applications which require monitoring of joint angles. The technique is not dependent on a fixed reference coordinate system and thus may be suitable for use in a dynamic system such as a moving vehicle. The technique was evaluated by applying it to joint angle measurement of the ankle joint. Experimental results show that accurate measurement of ankle joint angles is achieved by the technique during a variety of lower leg exercises including walking.

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A telemonitoring system, based on short message service (SMS), has been developed to remotely monitor the long-term mobility levels of elderly people in their natural environment. Mobility is measured by an accelerometer-based portable unit, worn by each monitored subject. Mobility level summaries are transmitted hourly, as an SMS message, directly from the portable unit to a remote server for long-term analysis. Each subject's mobility levels are monitored using custom-designed mobility alert software, and the appropriate medical personnel are alerted by SMS if the subject's mobility levels decrease.

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Rapid technological advances have prompted the development of a wide range of telemonitoring systems to enable the prevention, early diagnosis and management, of chronic conditions. Remote monitoring can reduce the amount of recurring admissions to hospital, facilitate more efficient clinical visits with objective results, and may reduce the length of a hospital stay for individuals who are living at home. Telemonitoring can also be applied on a long-term basis to elderly persons to detect gradual deterioration in their health status, which may imply a reduction in their ability to live independently. Mobility is a good indicator of health status and thus by monitoring mobility, clinicians may assess the health status of elderly persons. This article reviews the architecture of health smart home, wearable, and combination systems for the remote monitoring of the mobility of elderly persons as a mechanism of assessing the health status of elderly persons while in their own living environment.

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The training and competition regimen of elite athletes demands rapid feedback about their performance. The aim of this study was to determine if real-time visual ipsative (comparison with oneself) feedback of instantaneous kinematic consistency improves overall kinematic consistency in rowing. Accelerometry-based data, representing the upper and lower body kinematics, were determined for 13 experienced rowers. Kinematic consistency data -- represented by percentage time outside the acceptable performance bandwidth, performance consistency -- represented by power-stroke dispersion, and several performance indicators were acquired for all the rowers for three 2000 m time trials on a RowPerfect ergometer with three different visual feedback interventions: no feedback, detailed feedback, and summary feedback. Results indicated significantly increased performance consistency for detailed feedback than for both no feedback (p < 0.01) and summary feedback (p < 0.05). No significant difference between summary feedback and no feedback was found (p = 0.173). We deemed feedback of detailed information to enhance kinematic consistency significantly more than both no feedback (p < 0.01) and summary feedback (p < 0.01) interventions, although summary feedback was shown to enhance kinematic consistency more than no feedback (p < 0.01). No improvements were found for performance-related parameters.

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Long distance travel is associated with increased risk of deep vein thrombosis (DVT). There is an increased risk of travel related DVT in passengers with a predisposition to thrombosis. Assisting blood circulation in the lower limb will reduce the risk of DVT. Leg exercises are recommended as a DVT preventative measure while flying but this fails to account for a passenger who is distracted by in flight entertainment or who falls asleep for an extended period. A method for monitoring calf muscle pump activity using accelerometers has been developed and evaluated. The proposed technique could be used to alert the traveller that there is a need to exercise their calf muscle, thus reducing the risk of DVT.

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The electromyographic (EMG) signal provides information about the performance of muscles and nerves. At any instant, the shape of the muscle signal, motor unit action potential (MUAP), is constant unless there is movement of the position of the electrode or biochemical changes in the muscle due to changes in contraction level. The rate of neuron pulses, whose exact times of occurrence are random in nature, is related to the time duration and force of a muscle contraction. The EMG signal can be modeled as the output signal of a filtered impulse process where the neuron firing pulses are assumed to be the input of a system whose transfer function is the motor unit action potential. Representing the neuron pulses as a point process with random times of occurrence, the higher order statistics based system reconstruction algorithm can be applied to the EMG signal to characterize the motor unit action potential. In this paper, we report results from applying a cepstrum of bispectrum based system reconstruction algorithm to real wired-EMG (wEMG) and surface-EMG (sEMG) signals to estimate the appearance of MUAPs in the Rectus Femoris and Vastus Lateralis muscles while the muscles are at rest and in six other contraction positions. It is observed that the appearance of MUAPs estimated from any EMG (wEMG or sEMG) signal clearly shows evidence of motor unit recruitment and crosstalk, if any, due to activity in neighboring muscles. It is also found that the shape of MUAPs remains the same on loading.

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The prosthetic activity monitor (PAM) is an instrument to assess over the long-term the duration and spatio-temporal characteristics of walking of amputees, during normal daily life. In this study, the validity of PAM-derived measurements was investigated. Twelve transtibial amputees performed an activity protocol, consisting of stationary and walking activities, and activities associated with nonlocomotor movements. The protocol also included potential sources of error and activities assumed to be prone to misdetection. Measurements consisted of the PAM and video recordings. Agreement between video analysis and PAM output was the main outcome measure. The PAM generally correctly classified stationary activities (100% inactive, 0% active, 0% locomotion), nonlocomotor activities (45% inactive, 55% active, 0% locomotion) and walking activities (0% inactive, 1.8% active, 98.2% locomotion). When walking, the number of strides taken was slightly underestimated (-1.0%). The underestimation of distance travelled (-6.2%) and walking speed (-5.8%) was greater. The agreement with video output decreased when the PAM was misaligned, when persons walked at a speed below the defined minimum speed, and when persons walked with crutches. The PAM provides valid data on activity classes and number of strides. Although the majority of the distance data was satisfactory, in some cases considerable differences were found between the PAM and the video data. The impact of alignment, walking speed, and use of assistive devices on the PAM's operation should be considered.

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Drop foot stimulators today operate open loop with a trapezoidal stimulation profile. The traditionally applied profile originated as much from technological constraints as suitability for the physical pathology. It was proposed that by increasing the stimulation intensity during the loading response phase of gait, the ankle angle trajectory would become closer to that of normal gait and a more efficient heel rocker would be introduced. One patient, who used an implanted stimulator, was tested. Various profiles, which provided increased stimulation during loading response, were tried and joint angle trajectories, electromyograms, and footswitches were recorded. Statistical analysis was performed using a one way anova and posthoc Tukey tests. The experiment showed that increasing stimulation intensity during loading response increased the duration of the heel rocker. Statistical analysis revealed that this was significant at p = 0.05 level. Increasing stimulation intensity during loading response prolongs the heel rocker. This is an essential mechanism for advancement over the stance limb and providing shock absorption during weight acceptance, thus, we conclude that this improves the gait pattern of the drop foot sufferer.

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Current sensors for the control of functional electrical stimulation (FES) assisted walking in hemiplegic individuals are not wholly satisfactory, as they are either not implantable or ineffectual in the detection of heel contact events. This study describes the use of an accelerometer placed on the trunk to detect heel contact events of both legs based on the examination of the anterior-posterior horizontal acceleration signal. Four subjects wore an accelerometer over their lumbar spine. Footswitches placed on the sole of one foot recorded the heel contact and heel off times for that foot. The acceleration signal was reduced to a series of pulses by studying the negative-positive changes in acceleration. It was found that there was approximately a 150 ms delay between heel contact and the negative-positive change in acceleration. This delay was consistent across different walking speeds, but was different between subjects and when hemiplegic gait was simulated. Therefore, accelerometers placed on the trunk are valid sensors for the detection of heel contact events during FES assisted walking.

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An optimized stimulation intensity envelope for use in hemiplegic drop foot applications has been developed. The traditional trapezoidal stimulation intensity approach has been examined and found to be inconsistent with the muscle activity patterns observed in healthy gait and therefore unsuitable. Experimental functional electrical stimulation (FES)-elicited tibialis anterior (TA) electromyography (EMG) data was taken over the ankle range of interest (occurring during active dorsiflexion and loading response) while also taking into account the type of TA muscle contraction occurring (concentric, eccentric, and isometric) and the speed of hemiplegic ankle joint rotation. Using the processed data, a model of normalized EMG versus pulsewidth was developed. Implementation of this model showed the unsuitability of the trapezoidal approach in the reproducing of a natural EMG profile. An optimized stimulation intensity profile is proposed which is expected to accurately reproduce the natural TA EMG profile during gait.

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This paper reviews the technological developments in neural orthoses for the correction of upper motor neurone drop foot since 1961, when the technique was first proposed by Liberson and his co-workers. Drop foot stimulator (DFS) developments are reviewed starting with hard-wired single-channel and multichannel surface functional electrical stimulation (FES) systems, followed by implanted drop foot stimulators, and then continuing with microprocessor-based surface and implanted drop foot stimulators. The review examines the role of artificial and "natural" sensors as replacements for the foot-switch as the primary control sensor in drop foot stimulators. DFS systems incorporating real-time control of FES and completely implanted DFS systems finish the review.

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