Circadian parameter as a possible indicator of gait performance and daily activity levels in chronic stroke survivors.

Stroke recovery is a critical public health problem. It involves cognitive and physical impairments leading to physical inactivity. In addition, there are also sleep problems and disruption of the circadian rhythm. In this paper, we analyze the relation between cognitive impairments level, walking performance, sleep and circadian parameters of a group of chronic stroke survivors. Five stroke survivors enrolled in the study. The clinical assessments were: cognitive function (MoCA), the 10 meter-walking test (10MWT), and the 6 minutes walking test (6MWT). The circadian rhythm parameters were obtained for at least one week wearing the actimeters. There was a positive correlation between the duration of the main sleep episode and the MoCA scores. There were significant correlations between the 10MWT and 6MWT and the circadian parameters that were positive for most active period (M10), Interdaily stability (IS), Mesor and Amplitude and negative for intradaily variability (IV). Our results indicate that gait speed and resistance are correlated to circadian rhythm synchronization, lower rhythm variability and more defined activity-rest episodes. This preliminary study underscores the importance of including a continuous measure of sleep and activity cycles in the assessment of stroke survivors.

Elbow movement estimation based on EMG with NARX Neural Networks.

The use of the electrical activity from the muscles may provide a natural way to control exoskeletons or other robotic devices seamlessly. The major challenges to achieve this goal are human motor redundancy and surface electromyography (sEMG) variability. The goal of this work is to find a feature extraction and classification procedures to estimate accurately elbow angular trajectory by means of a NARX Neural Network. The processing time-step should be small enough to make it feasible its further use for online control of an exoskeleton. In order to do so we analysed the Biceps and Triceps Brachii data from an elbow flexo-extension Coincident Timing task performed in the horizontal plane. The sEMG data was pre-processed and its energy was divided in five frequency intervals that were fed to a Nonlinear Auto Regressive with Exogenous inputs (NARX) Neural Network. The estimated angular trajectory was compared with the measured one showing a high correlation between them and a RMSE error maximum of 7 degrees. The procedure presented here shows a reasonably good estimation that, after training, allows real-time implementation. In addition, the results are encouraging to include more complex tasks including the shoulder joint.

Assessment of postural control after sleep deprivation with a low-cost portable force plate.

It is well-known that acute sleep deprivation affects negatively postural control. The analysis of sleep quality during long periods and its impact on motor control and learning performance are crucial aspects of human health. Nevertheless, there is conflicting evidence regarding which postural control variables are more prone to change due to sleep deprivation. Moreover, very few clinicians have at their disposal expensive force plates to measure such variables, so the use of a low-cost portable device could be very interesting. Therefore, we aimed to identify which posture control variables, obtained from a low-cost plate, are more sensitive to sleep deprivation. In order to do so, we have performed a set of experiments with volunteers before and after a night without sleep. Eight participants took part of the study and had their balance measured by a Wii Balance Board before and after one night of sleep deprivation. They were asked to keep a quiet stance on top of the plate with their eyes open and closed, in a balanced design. The main results showed that, regardless the visual information, sleep deprivation has deepest impact on the anterior-posterior center of pressure displacement. Sleep deprivation without visual information had a more pronounced (large effect size) impact on the mean sway in the anterior-posterior direction and its distribution variation. The information that sleep deprivation has a more meaningful impact on anterior-posterior center of pressure excursion may help clinicians and healthcare professionals to better deal with its implications.

EMG-Based Control in a Test Platform for Exoskeleton with One Degree of Freedom.

There are several efforts to use the electrical signals generated by the human muscles to control virtual or even physical devices. It is expected that, the development of this method will provide a natural way to control these devices, requiring little user training, depending on the task complexity. With respect to the control of exoskeletons from the electric signals generated by the muscles, it is desirable that the exoskeleton acts in synergy with the user using surface electromyography (sEMG) signals to detect user intentions. One of the challenges of this approach is the variability of the sEMG signals due to factors such as electrode positioning and conditions of the volunteer at the time of acquisition. In previous work, a procedure based on an Autoregressive with Exogenous Input (ARX) linear model was developed to translate sEMG from biceps, triceps and brachioradialis muscles to elbow joint angle. In this work, we developed a method based on a Genetic Algorithm (GA) to update the ARX model coefficients online to minimize the training periods and we have used the EMG signals to control a one-degree of freedom exoskeleton.vThe GA was able to obtain ARX model coefficients that generate the joint angle reference from the EMG signals. In addition, the joint angle references generated from the offline sEMG from three muscles via an ARX model were used to control a device. At this point we are carrying out tests with the exoskeleton using real-time signals from sEMG.

Elbow Joint Angle Estimation with Surface Electromyography Using Autoregressive Models.

This paper presents a method to estimate the elbow joint angle from surface electromyography (sEMG) measurements of biceps, triceps and brachioradialis. This estimation is of major importance for the design of human robot interfaces based on sEMG. It is also relevant to model the muscular system and to design biomimetic mechanisms. However, the processing and interpretation of electromyographic signals is challenging due to nonlinearities, unmodeled muscle dynamics, noise and interferences. In order to determine an estimation model and a calibration procedure for the model parameters, a set of experiments were carried out with six subjects. The experiments consisted of series of continuous (cyclical) and discrete elbow flexo-extensions with three different loads (i.e. 0 kg, 1.5kg and 3 kg). The sEMG data from the biceps brachii, triceps brachii and brachioradialis and the joint angle were recorded. Four different modeling techniques were evaluated: State Space (SS), Autoregressive with Exogenous Input (ARX), Autoregressive Moving-Average with Exogenous Input (ARMAX), Autoregressive Integrated Moving-Average with Exogenous Input (ARIMAX). After the model was selected, a second experiment was performed in order to validate the estimation procedure. The results show a procedure to estimate the EMG-to-angle relation with high correlation and low meansquare- root errors with respect to the measured angle data.

Daytime sleepiness affects gait auditory synchronization ability.

Sleep disturbances in modern life lead to cognitive and motor performance impairments in everyday tasks such as gait. The most common symptom of these disturbances is daytime sleepiness, which can be assessed by questionnaires such as the Epworth Sleep Scale (ESS). The ESS evaluates sleep health and daytime dysfunction. The goal of this study is to assess the influence of sleepiness on a motorauditory synchrony task, rhythmed gait. High and low sleepiness clusters were formed based on the participants ESS scores. Walking on a treadmill, two different rhythmic auditory stimulus conditions were set with a metronome: isochronous and non-isochronous. Reflective markers on both heels with seven infrared cameras were used to assess the difference between footfall and metronome beep, what is named synchronization error (SE). There was a tendency to anticipate the beep in the HS group when compared to the LS group only in the non-isochronous stimulus condition that was statistically significant. Sleep disturbances that generate daytime sleepiness may bring detrimental effects on brain areas that could be responsible for the real-time adjustment of gait and sustained attention. These impairments may be responsible for the larger synchronization error with larger relative phase of the group with high sleepiness. More studies are necessary involving other parameters of sleep and gait to identify sleep disturbances through gait analysis.

Biomechanical procedure to assess sleep restriction on motor control and learning.

The analysis of sleep quality during long periods and its impact on motor control and learning performance are crucial aspects for human health. The aim of this study is to analyze effects of chronic sleep restriction on motor performance. It is intended to establish motor control indicators in sleep quality analysis. A wearable actigraphy that records accelerometry, ambient light, and body temperature was used to monitor the sleep habits of 12 healthy subjects for two weeks before performing motor control and learning tests. The day of the motor test, the subjects filled two questionnaires about the quality of sleep (Pittsburgh Sleep Quality Index - PSQI) and sleepiness (Epworth Sleepiness Scale - ESS). Afterwards they performed a coincident timing task that consisted of hitting a virtual target falling on the screen with the hand. An elbow flexion in the horizontal plane had to be performed on the correct time to reach the real target on a table at the same time as the virtual target on the screen. The subjects performed three sets of acquisition and transfer blocks of the coincident timing task. The subjects were clustered in two groups based on the PSQI and ESS scores. Actigraphy and motor control parameters (L5, correct responses, time variance) were compared between groups and experimental sets. The group with better sleep parameters did show a constant performance across blocks of task acquisition while the bad sleeper group improved from the first to the second acquisition block. Despite of this improvement, their performance is not better than the one of the good sleepers group. Although the number of subjects is low and it should be increased, these results indicate that the subjects with better sleep converged rapidly to a high level of performance, while the worse sleepers needed more trials to learn the task and their performance was not superior to the other group.

Recovery response latencies to tripping perturbations during gait decrease with practice.

There are several control mechanisms that contribute to keep gait stability under the presence of perturbations. For larger perturbations, responses with longer latencies produce adequate reactions to the perturbation. Latencies might be shorter, and the risk for falling might decrease provided that the reaction is adequate. It is possible that training the recovery responses through a sequence of perturbations induce some changes in the reactions. The goal of this paper is to test if the recovery response mechanisms might change during a training session with multiple perturbations. Differences in the recovery reactions executed at the beginning and at the end of a sequence of perturbations were analyzed. The latency of the burst in the Rectus Femoris (RF), measured with surface EMG (sEMG), showed a significant reduction during the course of the experimental session. When trials are repeated, subjects are able to generate a more appropriate response to the perturbations.

Lipedema: an overview of its clinical manifestations, diagnosis and treatment of the disproportional fatty deposition syndrome - systematic review.

Lipedema is a disproportionate, symmetrical fatty swelling characterized by pain and bruising existing almost exclusively among women. We undertook a systematic review of the available literature about lipedema, given the lack of knowledge and little evidence about this disorder especially among obesity experts. Diagnosis of lipedema is usually based on clinical features. Symmetrical edema in the lower limbs with fatty deposits located to hips and thighs usually appears at puberty and often affects several members of the same family. Main disorders considered for differential diagnosis are lymphedema, obesity, lipohypertrophy and phlebedema. Treatment protocols comprise conservative (decongestive lymphatic therapy) and surgical (liposuction) approaches. Early diagnosis and treatment are mandatory for this disorder otherwise gradual enlargement of fatty deposition causes impaired mobility and further comorbidities like arthrosis and lymphatic insufficiency.

Aplicación del análisis tridimensional de la marcha en pacientes con síndrome centromedular / Application of gait 3d analysis in patients with central cord syndrome

Introducción. El síndrome centromedular es el más común de las lesiones medulares incompletas y el 87-97% de estos pacientes consiguen una marcha independiente, pero no se han encontrado estudios publicados sobre el análisis de la marcha. El objetivo de este estudio fue analizar las características de la marcha de sujetos con síndrome centromedular y comparar los resultados con un grupo control formado por individuos sanos de características antropométricas similares. Métodos. Se analizó a 12 pacientes con síndrome centromedular y a un grupo control formado por 20 sujetos. Los datos cinemáticos se obtuvieron con un sistema de análisis tridimensional del movimiento. El grupo control caminó a velocidad libre y a velocidad similar a la registrada en los pacientes. Las variables espaciotemporales y cinemáticas se compararon entre los dos grupos. Resultados. La abducción de cadera y la flexión de rodilla en el contacto inicial, así como el mínimo de flexión de rodilla durante la fase de apoyo, fueron mayores en el grupo de pacientes (p<0,05). Sin embargo, los rangos de movimiento de la rodilla y el tobillo en el plano sagital fueron mayores en el grupo control (p<0,05). Conclusiones. El patrón de la marcha de los pacientes mostró una disminución del rango de movimiento en el plano sagital de la rodilla y el tobillo y un incremento de la abducción de la cadera para incrementar la base de sustentación. Estos resultados pueden facilitar la planificación objetiva de los tratamientos encargados de mejorar la marcha en estos pacientes(AU)

Background. Central cord syndrome is the most common incomplete spinal cord injury syndrome and 87-97% of these patients achieve independent walking but no gait analysis studies have been reported. The aim of this study was to analyze the characteristics of the gait in subjects with central cord syndrome and to compare the results with a healthy anthropomorphically matched control group. Methods. Twelve patients and a control group with twenty subjects were analyzed. Kinematic data were obtained using a three-dimensional motion analysis system. The control group walked at a self-selected speed and at a speed similar to the speed previously registered in the patient group. Temporal, spatial variables and kinematic variables were compared between the two groups. Results. Hip abduction and knee flexion at initial contact as well as minimal knee flexion during stance were larger in the patient group (P<.05). However, knee and ankle ranges of motion in the sagittal plane were greater in the control group (P<.05). Conclusions. Knee and ankle range of motion in sagittal plane were reduced and hip abduction was increased to improve stability in patients with central cord syndrome. The results can support objective ways to establish the treatment to recover gait in patients with central cord syndrome(AU)

Linfedema: diagnóstico diferencial y pruebas complementarias / Lymphedema: Differential diagnosis and complementary tests

Objetivo: Realizar una revisión y actualización del diagnóstico diferencial del linfedema y de las pruebas complementarias necesarias y presentar un algoritmo simplificado del diagnóstico. Estrategia de búsqueda: Se buscaron los artículos originales en las principales bases de datos: National Guideline Clearinghouse, Guidelines Finder de la National Electronic Library for Health del NHS británico, Cochrane Central Register of Controlled Trials, Web of Knowledge y Medline (1996–2009), y las monografías más relevantes sobre linfedema. Selección de estudios: Se valoró la relevancia de los artículos mediante la lectura del título y resumen, y se analizó el texto completo de aquellos considerados relevantes. Datos: El edema de miembro inferior puede aparecer por múltiples causas y puede ser difícil de diagnosticar adecuadamente. Se deben descartar las causas sistémicas, como la insuficiencia cardiaca congestiva, la hipoalbuminemia, la insuficiencia renal, el síndrome nefrótico y la hepatopatía avanzada. Las causas locales, como el linfedema, el flebedema y el lipedema son más difíciles de diagnosticar (AU)

Objective: To review and update the existing knowledge regarding the differential diagnosis of lymphedema and the necessary complementary tests and to present a simplified algorithm for the diagnosis. Search strategy: A search was made of the original articles in the major databases: Clearinghouse National Guidelines, Guidelines Finder of the National electronic Library for Health of Britannic NHS, Cochrane Central Register of Controlled Trials, Web of Knowledge and MEDLINE (1996–2009), and for the most relevant monographs on lymphedema. Articles selection: The relevance of the articles was evaluated by initial reading of the title and abstract and the full text of those considered relevant was analyzed. Data: Lower limb edema may appear due to multiple causes and may be difficult to diagnose adequately. Systemic causes such as hypoalbuminemia, congestive heart failure, kidney failure, nephrotic syndrome and advanced liver disease need to be ruled out. Local causes such as lymphedema, phleboedema and lipedema are more difficult to diagnose (AU)

Linfedema: métodos de medición y criterios diagnósticos / Lymphedema: Measurement methods and diagnostic criteria

Objetivo: Realizar una revisión y una actualización de los conocimientos existentes respecto a los diferentes métodos de medición del linfedema y los criterios diagnósticos relacionados, cuestiones muy debatidas en las sociedades internacionales de linfología. Estrategia de búsqueda: Se buscaron los artículos originales en las principales bases de datos: Clearinghouse National Guidelines, Guidelines Finder de la National electronic Library for Health del NHS británico, Cochrane Central Register of Controlled Trials, Web of Knowledge y MEDLINE (1996–2009) y las monografías más relevantes sobre linfedema. Selección de estudios: Se valoró la relevancia de los artículos mediante la lectura del título y el resumen, y aquellos considerados relevantes fueron recuperados a texto completo para su análisis posterior. Datos: La medición del tamaño del miembro constituye el aspecto central del diagnóstico y la valoración del linfedema, pudiendo realizarse mediante medidas perimetrales (criometría) o volumetría directa o indirecta. Otras técnicas cuantifican aspectos como las propiedades mecánicas o físicas de los tejidos (AU)

Objective: To review and update the existing knowledge regarding the different methods of measurement of lymphedema and diagnostic criteria, these being very debated issues in international societies of lymphology. Search strategy: Original articles were searched for in major databases: Clearinghouse National Guidelines, Guidelines Finder of the National electronic Library for Health of Britannic NHS, Cochrane Central Register of Controlled Trials, Web of Knowledge and MEDLINE (1996–2009), and the most relevant monographs on Lymphedema. Study selection: The relevance of the articles was evaluated by initial reading of the title and abstract and the full text of those considered relevant was analyzed. Data: The main aspect of the diagnosis and assessment of lymphedema is the measurement of the size of the limb that can be done by circumference measurement or by direct or indirect volumetry. Other methods assess physical or mechanical properties of tissues (AU)

Study of the motion artefacts of skin-mounted inertial sensors under different attachment conditions.

A common problem shared by accelerometers, inertial sensors and any motion measurement method based on skin-mounted sensors is the movement of the soft tissues covering the bones. The aim of this work is to propose a method for the validation of the attachment of skin-mounted sensors. A second-order (mass-spring-damper) model was proposed to characterize the behaviour of the soft tissue between the bone and the sensor. Three sets of experiments were performed. In the first one, different procedures to excite the system were evaluated to select an adequate excitation stimulus. In the second one, the selected stimulus was applied under varying attachment conditions while the third experiment was used to test the model. The heel drop was chosen as the excitation method because it showed lower variability and could discriminate between different attachment conditions. There was, in agreement with the model, a trend to increase the natural frequency of the system with decreasing accelerometer mass. An important result is the development of a standard procedure to test the bandwidth of skin-mounted inertial sensors, such as accelerometers mounted on the skin or markers heavier than a few grams.

Posture control and complex arm coordination: analysis of multijoint coordinative movements and stability of stance.

The authors addressed the interactions between control of bimanual multijoint coordination tasks and posture. Participants (N = 6) performed 8 coordination patterns that differed in degree of complexity by using their bilateral elbows and wrists under 3 scaled motion speeds while standing on 2 force plates. Results indicated that producing complex bimanual multijoint coordinative tasks affected postural sway, thus resulting in an increase of sway activity. Behavioral as well as mechanical factors accounted for the increased disturbance in postural sway. Those findings suggest that performing complex coordination tasks disrupts postural control in normal young adults.

Describing gait as a sequence of states.

Traditionally, gait analysis has been based on normalizing the stride time to a percentage and then averaging several strides measured under the same conditions. This procedure relies on the questionable assumptions that gait is a cyclic movement with superimposed noise and that there is no variability in the timing of activation or in the angles within the stride so no rescaling occurs during the percentage conversion. However, there is a fluctuation in the timings at which the peak values occur. A typical hallmark of this time-rescaling is the increase of the joint angle standard deviation when the angular velocity increases. The goal of this paper is to present a description of gait to avoid averaging without distorting the original curves. In addition, it allows the analysis of the fluctuation between consecutive strides. In this method, it is assumed that gait is quasi-periodic. The key point is the representation of gait by a state vector that evolves in time. This state vector can be used to calculate the instantaneous period and provides a measure of the time fluctuations between strides. The sequence of states method describes a quasi-periodic movement like gait with a continuous estimate of cycle time and provides measure of the deviations between cycles.

Inverse dynamics calculations during gait with restricted ground reaction force information from pressure insoles.

The number of consecutive strides that can be recorded in measurements of gait have been limited due to the number of force plates and dimensions of the measurement field. In addition, the feet are constrained to land on the force plates. A method to calculate the inverse dynamics from the motion and incomplete information from the ground reaction forces (GRF), vertical component and its application point, is presented and compared to the calculations based on force plate measurements. This method is based on the estimation of the three-dimensional GRF during walking with pressure insoles. RMS errors were lower than 20 W for knee joint power compared to those derived from force plate measurements. The errors were larger during double stance phase due to errors in the application point measured with the insoles. This method, with some technical improvement, could be implemented in new gait analysis protocols measuring several consecutive steps either on a treadmill or over ground, depending on the motion-measurement system, without constraining foot placement.

Principal component analysis of complex multijoint coordinative movements.

Principal components analysis (PCA) has not been very much in vogue within the field of movement coordination even though it is useful to reduce data dimensionality and to reveal underlying data structures. Traditionally, studies of coordination between two joints have predominantly made use of relative phase analyses. This has resulted in the identification of principal constraints that govern the Central Nervous System's organization and the control of coordination patterns. However, relative phase analyses on pairwise joints have some drawbacks because they are not optimal for revealing convergent patterns among multijoint coordination modes and for unraveling generic control strategies. In this paper, we present a method to analyze multijoint coordination based on the properties of PC, more specifically the eigenvalues and eigenvectors of the covariance matrix. The comparison between relative phase analysis and PCA shows that both provide similar and consistent results, underscoring the latter technique's sensitivity to the study of coordination performance. In addition, it provides a method for automatic pattern detection as well as an index of performance for each joint within the context of the global coordination pattern. Finally, the merit of the PCA technique within the context of central pattern generators (CPG) will be discussed.

Energy analysis of human stumbling: the limitations of recovery.

This study has analyzed the segmental energy changes in the recovery from a stumble induced during walking on a treadmill. Three strategies emerged according to the behavior of the perturbed limb, elevating, lowering, and delayed lowering. These three strategies showed different changes in the segmental energy with respect to normal gait. In the elevating strategy, the energy loss induced by the stumble was restored during the perturbed step and reached normal levels during the recovery step. The largest energy changes occurred in the lowering and delayed lowering strategies during the double stance (DS) phase. Moreover, in some of these trials there was energy absorption during the double stance phase for several strides after the perturbation. The most challenging perturbations had longer duration or occurred at mid-swing, triggering delayed lowering or lowering strategies, because more strides and larger energy changes were needed to recover, suggesting a trade-off between stability and energy efficiency.

Use of pressure insoles to calculate the complete ground reaction forces.

A method to calculate the complete ground reaction force (GRF) components from the vertical GRF measured with pressure insoles is presented and validated. With this approach it is possible to measure several consecutive steps without any constraint on foot placement and compute a standard inverse dynamics analysis with the estimated GRF.

Valoración del daño corporal en la lesión medular: diferencias entre tetrapléjicos y parapléjicos / Assessment of body damage in the spinal cord injuries: differences between tetraplegics and paraplegics

Introducción. La valoración del lesionado medular se realiza con la escala de la American Spinal Injury Association (ASIA) para medir el déficit, la Medida de la Independencia Funcional (MIF) (Functional Independence Measure, FIM) para medir discapacidad, el Baremo de la Ley 30/95 para indemnizar las secuelas y las tablas de minusvalía. El objetivo de este estudio fue analizar las diferencias existentes en la valoración entre un grupo de pacientes con lesión medular cervical y otro dorsal, mediante estas cuatro escalas de valoración. Pacientes y método. Se incluyeron 19 pacientes varones con lesión medular completa traumática, 7 tetrapléjicos C6 y 12 parapléjicos entre D2-D11, con una media de edad de 23,2 años. Se evaluaron con las 4 escalas y se definió un modelo matemático, el "grado de diferencia relativa", para cuantificar objetivamente el grado de diferencia que presentan las escalas entre tetrapléjicos y parapléjicos. Resultado. Todas las escalas presentan diferencias en la puntuación entre tetrapléjicos y parapléjicos (p < 0,0001) y todas mantienen una asociación lineal entre sí y con la puntuación motora de la escala ASIA, siendo la MIF (R de Pearson: 0,924) y el baremo de tráfico (R: -0,887) las que presentan un mayor índice de correlación. Al calcular el grado de diferencia relativa, la MIF detecta una diferencia del 42 por ciento entre tetrapléjicos y parapléjicos; la escala ASIA un 29,8 por ciento, el baremo el 13,1 por ciento y las tablas de minusvalía sólo el 2,4 por ciento. Conclusiones. Las diferencias encontradas en el baremo y en las tablas de minusvalía entre tetrapléjicos y parapléjicos no se ajustan a las diferencias clínicas y funcionales existentes entre ellos (AU)