Several training methods have been developed to obtain motion information during real-time walking and feed it back to trainees who adjust their gait to ensure that the measured gait parameters approach target value, which may not always be suitable for every trainee owing to physical differences between individuals. This paper proposes a method of setting this target value considering these physical differences and discusses the usefulness of the gait training method, wherein a multichannel deep convolutional neural network (MC-DCNN) gait classification model constructed by learning ideal or non-ideal gait features beforehand is used for trainee gait classification. Activation maximization is applied to the MC-DCNN model; data wherein the ideal walking features are activated are generated based on trainee gait data. However, the amounts of features to be activated to generate a possible and natural gait are restricted. The original trainee gait, beyond individual physical differences, and gait data generated based on the original gait data seem to yield the target value considering the physical differences among individuals. This study focused on gait related to stumbling. To verify its usefulness, a multivariate gait dataset consisting of kinematic and kinetic indices labeled as "gait rarely associated with stumbling" or "gait frequently associated with stumbling" was divided into a training set, validation set, and test set. The MC-DCNN model learned gait features for multivariate gait data classification in the training set. It classified the gait with 96.04±0.12% accuracy against the validation set. Finally, by applying the proposed method to the multivariate gait data contained in the test set, we generated multivariate gait data classified as "gait rarely associated with stumbling" based on the input data. In addition, the generated multivariate gait data include motion that increases the thumb-to-ground distance and describe possible and natural gait considering the physical differences among individuals.

Keywords

Healthcare, Gait training, Motion analysis, Walking factor, Neural network, Activation maximization

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Carbon fiber running-specific prostheses (RSPs) are widely used among lower-limb amputee runners. However, which prosthesis provides the best performance for runners remains unknown. For this purpose, a computational model of the human body with a prosthesis was created and the effect of the prosthetic parameters on performance was investigated. First, motion capture systems were used to collect motion data from amputees. Furthermore, marker and force plate data were obtained to create a digital human model. Kinematic data such as limb lengths and joint angles were calculated using marker data. Afterward, the inertial properties were estimated to conduct inverse dynamic analyses. After building a computational model of amputee sprinting, the joint positions and ground reaction forces (GRFs) were compared with the experimental results. The design parameters of the prosthesis were introduced to understand the effects of the prosthesis on motion and performance. The response surface method was used to express motion adaption regarding the geometry and stiffness of the prosthesis. Hip and knee sagittal joint angles were updated based on the response surface method to simulate joint motion adaptations of the worn prosthesis. Additionally, average horizontal velocity, horizontal velocity change over one gait cycle, vertical and horizontal impulses were considered as performance functions. An evaluation parameter was proposed to generalize the idea of performance. The moment of the prosthetic knee and the closest point of the prosthesis to the ground during the swing phase were defined as design constraints to consider knee buckling and prosthetic leg tripping, respectively. The effect of the design parameters on the performance and constraint functions was also investigated and a method to determine and design a suitable prosthesis for an individual was proposed. It was revealed that proper selection and design of prostheses represent an important way to increase performance.

Keywords

Amputee running, Running-specific prosthesis, Prosthetic parameters, Running performance, Multilink model, Motion capture

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As visual stimuli for exercise and cognitive rehabilitation of biomechanics, virtual reality (VR) and augmented reality (AR) devices have getting popularity. In the process of developing the relevant content for VR and AR, there has been a problem that only a specific platform must be supported or multiple programs must be used. Recently, the Unity 3D platform has been developed for the convenience of game development for VR or AR environments that potentially solve these problems. Unity 3D's game engine and animation can easily implement a moving avatar as visual stimuli, and the speed of the avatars can be checked in real-time. Therefore, we developed a moving avatar as the visual stimuli using Unity 3D and conducted pilot experiments with four healthy subjects by performing the knee extension and ankle dorsiflexion tasks with and without visual stimuli. The number of movements was counted to check the feasibility of the effectiveness using visual stimuli using Unity 3D. The results showed that the number of movements was higher when the visual stimuli were presented compared to that without the visual stimuli in both ankle dorsiflexion and knee extension. Our findings and approach can be a basis for further developing rehabilitation training protocols using various visual stimuli with Unity 3D.

Keywords

Biomechanics, Rehabilitation, Unity 3D, Game engine, Knee extension, Ankle dorsiflexion

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This paper discussed if a powered attendant propelled wheelchairs (PAPW) with assist-as-needed control reduces energy consumption and maximise attendant's physical activity in powered system use. This study introduced a PAPW with force velocity assist control (FVAC) based on individual capability of pushing force velocity relationship. This PAPW assists attendant pushing when more pushing force is needed over usual range of individual physical capabilities of pushing. With the PAPW, we investigated the performance of the FVAC and compared it with proportional assist control (PAC) on a flat level surface and a longitudinal slope (6.5%) with three participants. The experimental results showed that the PAPW with the FVAC reduced 50% of pushing force on the slope and this was similar performance of the PAC in terms of assisting. The FVAC also reduced 79% of mean mechanical assisting power on the flat against the PAC. These results support that the PAPW with the FVAC has flexibilities to adapt to individual physical capabilities and provides certain level of physical activities with sufficient assisting when needed, and low energy consumption for long time and distance operations for attendants.

Keywords

Assist-as-needed control, Assistive device, Attendant-propelled wheelchair, Force-velocity relationship, Iindividual physical capability

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We investigated how the chemotactic behaviors of peritrichous bacteria that repeat straight swimming (runs) and directional changes (tumbles) differ depending on the chemical species and concentrations of the attractant. Quantification of the intensity of bacterial chemotaxis will be helpful for the prediction of the bacterial accumulation. We conducted microscopic observation of Salmonella typhimurium cells around a capillary filled with the attractant, L-aspartic acid or L-serine. At the same concentration, cells accumulate more rapidly around L-aspartic acid than L-serine, and the accumulation region around L-aspartic acid is larger than L-serine. Then we estimated the intensity of chemotaxis by comparison with the mathematical model, where characteristic behavior in the run-and-tumble motion of chemotactic bacteria is modeled; the cell decreases the tumble frequency when the cell swims toward the direction where the attractant concentration increases. Observed number density of cells is well approximated with exponentially decaying function of the distance from the capillary tip, which is similar trend to the simulation based on the mathematical model. The intensity of chemotaxis, determined from the slope of the exponential distribution, is almost the same regardless of the chemical species of the attractant or the concentration of L-serine or L-aspartic acid. It can be said that the behavior of a single bacterial cell (probability of suppressing tumble) is almost the same in the region where the cell senses the concentration gradient of the attractant, and that higher concentration of the attractant affects mainly the larger detectable region of the attractant.

Keywords

Peritrichous bacterium, Chemotaxis, Run and tumble, Random walk, Capillary assay

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Although it has been reported that blood brain barrier (BBB) disruption following head impact can lead to increased vascular permeability and subsequent brain injury, the influence of pressure loading on BBB dysfunction is not fully understood. In this study, we exposed in vitro BBB models to impulsive pressure to mimic changes in intracranial pressure during head impact. Barrier function was examined by measuring transendothelial electrical resistance (TEER). Four models were used: an endothelial monolayer of rat brain capillaries (E00 model), a co-culture model of endothelial cells and pericytes (EP0 model), a co-culture model of endothelial cells and astrocytes (EA0 model), and a triple co-culture model of endothelial cells, pericytes, and astrocytes (EPA model). Immediately after loading, the E00 model showed a 13% decrease in TEER, the EP0 model showed an 8% decrease, the EA0 model showed a 40% decrease, and the EPA model showed a 33% decrease. At 2 days post-loading, TEER values in the EPA model remained decreased and the expression of claudin-5 and ZO-1 was significantly decreased, whereas GFAP expression was significantly increased. In conclusion, increased endothelial paracellular permeability induced by exposure to impulsive pressure is associated with astrocyte activation and decreased tight junction protein expression in vitro.

Keywords

Head impact, Endothelial permeability, Transendothelial electrica resistance, Brain capillary

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The high sensitivity of mammalian hearing is achieved by cochlear amplification. The basis of this amplification is the motility of outer hair cells (OHCs), which are sensory cells in the inner ear. This motility may be due to voltage-dependent conformational changes of the motor protein prestin, which is densely embedded in the lateral membrane of OHCs. However, the membrane structure of prestin has not yet been elucidated. Therefore, the membrane structure of prestin was herein investigated by force spectroscopy using an atomic force microscope (AFM). The gene of prestin fused with an Avi-tag at its C terminus was transfected into Chinese hamster ovary (CHO) cells and the inside-out plasma membrane was isolated. The Avi-tag was enzymatically biotinylated and attached to a streptavidin-coated AFM cantilever via biotin-streptavidin binding. Prestin was then pulled out from the plasma membrane and the relationship between the force applied to the protein and the extension distance, i.e., the force-extension (FE) curve, was assessed. The curves obtained showed saw-toothed patterns. An attempt was then made to analyze these curves using the worm-like chain model. The force caused by stretching of the intracellular C terminus and that due to the extraction of one or several transmembrane domains were identified. The present results imply that the C terminus and the subsequent transmembrane domains of prestin correspond to those of the previously reported model with 12 transmembrane domains.

Keywords

Prestin, Motor protein, Inner ear, Membrane protein, Force spectroscopy, Hearing

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Hand prostheses by upper limb amputees are primarily dependent on visual feedback owing to the loss of sensory function in their hand. Although previous researches have been conducted on the restoration of the sensory function of amputees and on the development of electronic skin and gloves for sensory feedback, the realization to apply the research results to commercial hand prostheses is still difficult. In this study, we designed and developed a hand prosthesis cover including a sensory recognitive function which closely mimics human hand skin and, resulting into a multi-degree-of-freedom (DOF) myoelectric hand prosthesis. The proposed cover was made of flexible silicon to mimic the human hand skin, which can measure a grip force of less than 50 N using a tactile sensing module. The tactile sensing module was developed using a force-sensitive resistor sensor, and solid silicone vacuum compression molding by embedding the sensor and wires inside the cover was introduced for the fabrication process. A developed finger module for multi-DOF myoelectric hand prostheses by imitating the anatomical structure and motion mechanism of a human finger was compared the performance of the developed cover with that of a commercial cover on the developed finger module of the myoelectric hand prosthesis. The metacarpophalangeal joint range of motion of the finger module with the proposed cover with a 1.5 mm thickness was measured from 0° to 60° and the flexion angular velocity was recorded as a value of 60°/710 ms, which are similar to those of the commercial cover. From the experiments, we found that the hand gestures and grip motions seem to be similar with the proposed and commercial covers. From the experiment, we can suggest that the developed cover with sensory recognition can be directly applied to multi-DOF myoelectric hand prostheses. Also, with a fast and simple commercialized process, widely usage for amputees with the developed hand prosthesis cover will be available.

Keywords

Hand prosthesis cover, Anthropomorphic, Sensory recognition, Tactile sensing module, Grip force

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A numerical approach is one of feasible ways to discover the biomechanics of hallux valgus deformity with various osteotomy and fixation strategies. In the present study, two types of finite element models for analyzing the biomechanical performances of hallux valgus treatment with plate fixations were developed including the single first metatarsal bone model and the musculoskeletal lower extremity model. There are four types of plate fixations that were used to correct the deformity of hallux valgus. The strengths and limitations of both the single first metatarsal bone model and the musculoskeletal lower extremity model were evaluated and discussed. The results revealed that the single metatarsal bone models can be used to quickly predict the biomechanical performances of different hallux valgus treatments. Additionally, the musculoskeletal lower extremity models can be used to predict the biomechanical performances of different hallux valgus treatments under a physiological loading. The plate fixations with the insertion of all locking screws revealed better osteotomy fixation stability and lower risk of the implant failure compared to the other fixations. Additionally, the plate fixations with the insertion of six bone screws had lower risk of the metatarsal bone failure compared to the plate fixations with the insertion of four bone screws. The six holes plate with the insertion of six locking screws was the best treatment among the four treatment strategies. The numerical models and simulation techniques developed in the present study can provide useful information for understanding the biomechanics of hallux valgus treatments.

Keywords

Hallux valgus, Fixation stability, Implant failure, Bone failure, Finite element analysis, Lower extremity

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The purpose of this study was to develop quantitative parameters using range of motion (ROM) of shanks, thighs and knees to evaluate the effect of deep brain stimulation (DBS) on gait performance and freezing of gait (FOG) of patients with advanced Parkinson's disease (PD). Three patients with FOG due to Parkinson's disease advanced who has received DBS were recruited. The recruited subjects were instructed to walk on a 100-meter path in three conditions: 60 Hz DBS (60 Hz), 130 Hz DBS (130 Hz) and no DBS (Off). Five inertial measurement unit sensors were attached to subjects' sacrum, bilateral shanks and thighs respectively. Quantified parameters included (1) spatial parameters: shanks, thighs and knees ROM (2) temporal parameters: stride time, stance time duration and double support time percentage (3) FOG severity: the percentage of FOG duration during path walking. Three subjects' ROM of right shank significantly increased in 60 Hz,130 Hz and Off order. Compared to 130 Hz, right shank ROM of subjects S1, S2 and S3 significantly increased 13.2%, 99.6% and 6.1% in 60 Hz, respectively. In temporal parameters results, only double support time percentage was significantly different between 60 Hz and 130 Hz in all three subjects. When compared to 130 Hz, the double support time percentage of S1 and S2 significantly decreased 6.3% and 18.4% in 60 Hz, and that of S3 significantly increased 4.4%. ROM of right shank and FOG severity were highly correlated (R² = 0.71). Shank ROM could represent subjects' gait performance under different stimulation conditions. Shank ROM could be treated as a reference for clinicians to evaluate gait performance and severity of FOG immediately when DBS frequency is adjusted. This study demonstrated the potential of using objective parameters to optimize the DBS through assessing the gait performance changes in the clinic.

Keywords

Deep brain stimulation, Freezing of gait, Range of motion

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Model-based three-dimensional(3D)/two-dimensional(2D) image registration methods have been widely applied in measuring 3D kinematics of the knee during dynamic activities. However, the combined effects of bone model compositions (radiodensity vs. homogeneous-density) and the number of fluoroscopic views on the measurement accuracy remained unclear. The current study evaluated experimentally the accuracy of the four model-based 3D/2D image registration configurations on the accuracy of measured knee kinematics, namely homogeneous-density model/single-plane image (HS), radiodensity model/single-plane image (RS), homogeneous-density model/biplane images (HB), and radiodensity model/biplane images (RB). Computed tomography (CT) of the knee and asynchronous biplane fluoroscopic images of the simulated knee motions were collected from a cadaveric knee joint for the evaluation of the registration configurations. The results showed that the use of biplane fluoroscopic images ensured mean absolute errors (MAE) below 0.3 mm and 0.9° in each motion component regardless of the types of bone models. Application of radiodensity model could generate digitally reconstructed radiographs more similar to the fluoroscopic images, diminishing MAE in all motion components and measurement bias. As a result, the RS configuration was capable of reconstructing the 3D knee joint angles with MAE comparable to those obtained using the HB configuration. Among the four tested configurations, the RB configuration was most accurate and least affected by the fast skeleton motions.

Keywords

Accuracy, Kinematics, 3D fluoroscopy, Image registration, Radiodensity, Knee, Multiple x-ray images

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[Advance Publication] (Proper information for citation will be announced after formal publication)