Adaptive real-time tool for human gait event detection using a wearable gyroscope

The development of robust algorithms for human gait analysis are essential to evaluate the gait performance, and in many cases, crucial for diagnosing gait pathologies. This work proposes a new adaptive tool for human gait event detection in real-time, based on the angular velocity recorded from one gyroscope placed on the instep of the foot and in a finite state machine with adaptive decision rules. The signal was segmented to detect 6 events: Heel Strike (HS), Foot Flat (FF), Middle Mid-Stance (MMST), Heel-Off (HO), Toe-Off (TO), and Middle Mid-Swing (MMSW). The tool was validated with healthy subjects in ground-level walking using a treadmill, for different speeds (1.5 to 4.5 km/h) and slopes (0 to 10%). The results show that the tool is highly accurate and versatile for the detection of all events, as indicated by the values of accuracy, average delays and advances (HS: 99.96%,-7.95 ms, and 9.85 ms; FF: 99.48%,-4.95 ms, and 9.35 ms; MMST: 98.26%, 36.54 ms, and 16.38 ms; HO: 98.87%,-22.71 ms, and 18.62 ms; TO: 95.95%,-6.80 ms, 14.38 ms; MMSW: 96.06%,-3.45 ms; 0.15 ms, respectively). These findings suggest that the proposed tool is suitable for the real-time gait analysis in real-life activities.- (POCI

Towards human-knee orthosis interaction based on adaptive impedance control through stiffness adjustment

Rehabilitation interventions involving powered, wearable lower limb orthoses that can provide high-challenging locomotor tasks for repetitive training sessions, mainly when assist-as-needed strategies, such as adaptive impedance control, are designed. In this study, the adaptive behavior was ensured by software control of the robotic stiffness involved in the human-knee orthosis interaction in function of the gait cycle and speed. To estimate the stiffness, we analyzed the interaction torque-angle characteristics with experimental data. The speed-stiffness dependency was more evident when high stiffness values are demanded by the user's effort. Experimental evidence from five healthy subjects highlight that the adaptive control strategy provides a more comfortable, natural motion, and kinematic freedom as compared to the trajectory tracking control, allowing the user to contribute to the gait training. Future insights cover the implementation of gravitational compensation and real-time estimation and control of all inner dynamic properties of the impedance control law.This work has been supported by the FCT - Fundacao para a Ciencia e Tecnologia - with the reference scholarship SFRH/BD/108309/2015, with the reference project UID/EEA/04436/2013, and by FEDER funds through the COMPETE 2020 - Programa Operacional Competitividade e Internacionalizacao (POCI) - with the reference project POCI-01-0145-FEDER-006941, and partially supported with grant RYC-2014-16613 by Spanish Ministry of Economy and Competitiveness

Powered knee orthosis for human gait rehabilitation: first advances

This paper presents a new system for a powered knee orthosis, that was designed to assist and improve the gait function of patients with gait pathologies. The system contains the orthotic device (embedded with sensors for angle and user-orthosis interaction torque measurements, and an electric actuator) and wearable sensors (inertial measurement unit, force sensitive resistors, and electromyography sensors), which allows the generation of smart rehabilitation tools and several motion assistive techniques. The main goal is to present a conceptual overview and functional description of the system and use scenarios of each component. The attachment mechanism of the orthosis to the limb is also highlighted, being composed of a straps system fixed in the mechanical links of the joint. It was noticed that users with distinct lower-limb morphologies can presents difficulties wearing the orthosis, since the device needs constant adjust to align the mechanical and human joints. The system was validated in ground-level walking on healthy subjects, with emphasis on the impact of the device in the user. The subjects reported that the orthosis is comfortable to use, easy to wear, and no issues were raised regarding the aesthetics of the device. Only the weight was assimilated as a possible hindrance (compensated in the future). Future challenges involve the inclusion of an ankle joint in the system and the use of the proposed tool in rehabilitation.This work is supported by the FCT - Fundacao para a Ciencia e Tecnologia - with the reference scholarship SFRH/BD/108309/2015, with the reference project UID/EEA/04436/2013, and by FEDER funds through the COMPETE 2020 - Programa Operacional Competitividade e Internacionalizacao (POCI) - with the reference project POCI-01-0145-FEDER-006941, and partially supported with grant RYC-2014-16613 by Spanish Ministry of Economy and Competitiveness

Gait event detection in controlled and real-life situations: repeated measures from healthy subjects

A benchmark and time-effective computational method is needed to assess human gait events in real-life walking situations using few sensors to be easily reproducible. This paper fosters a reliable gait event detection system that can operate at diverse gait speeds and on diverse real-life terrains by detecting several gait events in real time. This detection only relies on the foot angular velocity measured by a wearable gyroscope mounted in the foot to facilitate its integration for daily and repeated use. To operate as a benchmark tool, the proposed detection system endows an adaptive computational method by applying a finite-state machine based on heuristic decision rules dependent on adaptive thresholds. Repeated measurements from 11 healthy subjects (28.27 +/- 4.17 years) were acquired in controlled situations through a treadmill at different speeds (from 1.5 to 4.5 km/h) and slopes (from 0% to 10%). This validation also includes heterogeneous gait patterns from nine healthy subjects (27 +/- 7.35 years) monitored at three self-selected paces (from 1 +/- 0.2 to 2 +/- 0.18 m/s) during forward walking on flat, rough, and inclined surfaces and climbing staircases. The proposed method was significantly more accurate (p > 0.9925) and time effective ( 0.9314) in a benchmarking analysis with a state-of-the-art method during 5657 steps. Heel strike was the gait event most accurately detected under controlled (accuracy of 100%) and real-life situations (accuracy > 96.98%). Misdetection was more pronounced in middle mid swing (accuracy > 90.12%). The lower computational load, together with an improved performance, makes this detection system suitable for quantitative benchmarking in the locomotor rehabilitation field.This work has been supported in part by the Fundacao para a Ciencia e Tecnologia (FCT) with the Reference Scholarship under Grant SFRH/BD/108309/2015, by the Reference Project under Grant UID/EEA/04436/2013, and part by the FEDER Funds through the COMPETE 2020-Programa Operacional Competitividade e Internacionalizacao (POCI)-with the Reference Project under Grant POCI-01-0145-FEDER-006941, and in part by Spanish Ministry of Economy and Competitiveness Grant RYC-2014-16613

Can drug safety be predicted and animal experiments reduced by using isolated mitochondrial fractions?

Mitochondrial toxicity has resulted in the withdrawal of several drugs from the market. One particular example is nefazodone, an anti-depressant withdrawn in the USA due to hepatoxicity caused by drug-induced mitochondrial dysfunction. Drug development and safety testing can involve the use of large numbers of laboratory animals, which, without a decisive pre-screening for mitochondrial toxicity, are often unable to pre-empt higher mortality rates in some patient groups. The use of isolated mitochondria as a screening tool for drug safety can decrease the number of laboratory animals used in pre-clinical studies, thus improving animal welfare and healthcare outcomes and costs. Novel techniques involving high-throughput methods can be used to investigate whether a molecule is a mitochondrial toxicant. Moreover, these screens are mechanistically-based, since the effects of the drug on oxidative phosphorylation, calcium homeostasis and mitochondrial genetics can be assessed. This review is intended to demonstrate that isolated mitochondrial fractions are suitable for predicting drug and general chemical safety in toxicological screenings, thus contributing to the refinement and reduction of animal use in laboratory research

Calcium-dependent mitochondrial permeability transition is augmented in the kidney of Goto-Kakizaki diabetic rat

Renal disease associated with diabetes mellitus is a major problem among diabetic patients. The role of mitochondria in the pathogenesis of diabetes has received a large amount of attention in the last years, but many aspects of this subject are still poorly understood. In the present study, we studied the susceptibility of the mitochondrial permeability transition (MPT) on kidney mitochondria from the Goto-Kakizaki (GK) rat, an animal model featuring physiological and pathological alterations characteristic of type 2 diabetes.Kidney mitochondria were isolated by differential centrifugations; mitochondrial electric transmembrane potential and calcium loading capacity were evaluated with a TPP+-selective electrode and with a calcium-sensitive fluorescent probe. Coenzyme Q9, Q10 and vitamin E were evaluated by high-performance liquid chromatography (HPLC).Kidney mitochondria from the diabetic animals had an increased susceptibility to the induction of the MPT by calcium. We observed a loss of calcium-loading capacity and a higher calcium-induced mitochondrial depolarization. Vitamin E and coenzyme Q9 were also increased in kidney mitochondria from GK rats.The results show an enhanced MPT activation in kidney mitochondria from GK rats, which lead us to suggest that this condition may be one major alteration triggered by chronic diabetes in kidney cells, ultimately leading to cell dysfunction. Copyright © 2004 John Wiley & Sons, Ltd

EMG-based motion intention recognition for controlling a powered knee orthosis

Powered assistive devices have been playing a major role in gait rehabilitation. This work aims to develop a user-oriented assistive strategy with an EMG-based control using a powered knee orthosis (PKO) to provide assistive commands according to the user's motion intention tracked by electromyography (EMG) signals. To achieve this goal, the work first comprised the development of a wired EMG acquisition system, the study and implementation of a knee joint torque estimation method, and the development of a real-time controller, which uses the estimated torque as the reference actuator's torque to provide user-oriented assistance in walking. We used a proportional gain method to estimate the knee torque, which required a calibration procedure, allowing to determine the relation between the EMG signal and the actuator's torque. The EMG-based control was validated with two subjects walking in a treadmill. The EMG-based control performed as expected since it proved to be functional and time-effective when assisting the user's movements in walking at different walking speeds. Findings show that the developed assistive strategy can effectively follow the user's motion intention and has the potential for gait rehabilitation of patients with residual muscular strength.This work has been supported in part by the Fundacao para a Ciencia e Tecnologia (FCT) with the Reference Scholarship under Grant SFRH/BD/108309/2015, the reference project UID/EEA/04436/2019, by FEDER funds through the COMPETE 2020 - Programa Operacional Competitividade e Internacionalizacao (POCI) - with the reference Project POCI-01-0145-FEDER-006941; and the LIACC Project UID/CEC/00027/2019; and with national funds from FCT project SmartOs-under Grant NORTE-01-0145-FEDER-030386

Wearable inertial sensor system towards daily human kinematic gait analysis: benchmarking analysis to MVN BIOMECH

This paper presents a cost- and time-effective wearable inertial sensor system, the InertialLAB. It includes gyroscopes and accelerometers for the real-time monitoring of 3D-angular velocity and 3D-acceleration of up to six lower limbs and trunk segment and sagittal joint angle up to six joints. InertialLAB followed an open architecture with a low computational load to be executed by wearable processing units up to 200 Hz for fostering kinematic gait data to third-party systems, advancing similar commercial systems. For joint angle estimation, we developed a trigonometric method based on the segments’ orientation previously computed by fusion-based methods. The validation covered healthy gait patterns in varying speed and terrain (flat, ramp, and stairs) and including turns, extending the experiments approached in the literature. The benchmarking analysis to MVN BIOMECH reported that InertialLAB provides more reliable measures in stairs than in flat terrain and ramp. The joint angle time-series of InertialLAB showed good waveform similarity (>0.898) with MVN BIOMECH, resulting in high reliability and excellent validity. User-independent neural network regression models successfully minimized the drift errors observed in InertialLAB’s joint angles (NRMSE < 0.092). Further, users ranked InertialLAB as good in terms of usability. InertialLAB shows promise for daily kinematic gait analysis and real-time kinematic feedback for wearable third-party systems.This work has been supported in part by the Fundação para a Ciência e Tecnologia (FCT) with the Reference Scholarship under Grant SFRH/BD/108309/2015 and SFRH/BD/147878/2019, by the FEDER Funds through the Programa Operacional Regional do Norte and national funds from FCT with the project SmartOs under Grant NORTE-01-0145-FEDER-030386, and through the COMPETE 2020—Programa Operacional Competitividade e Internacionalização (POCI)—with the Reference Project under Grant POCI-01-0145-FEDER-006941

Anticholinesterase activity evaluation of alkaloids and coumarin from stems of Conchocarpus fontanesianus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conchocarpus fontanesianus (A. St.-Hill.) Kallunki & Pirani, Rutaceae, popularly known as pitaguara, is a native and endemic tree from Sao Paulo and Rio de Janeiro States, Brazil. Based in the information that anticholinesterasic derivatives could act as new prototypes to treatment of Alzheimer disease, this work describes the fractionation guided by evaluation of the anticholinesterase activity of the ethanolic stems extract from C. fontanesianus. This procedure afforded the alkaloids dictamnine (1), gamma-fagarine (2), skimianine (3), and 2-phenyl-1-methyl-4-quinolone (4), as well as the coumarin marmesin (5).222374380Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq