Walking speed estimation using foot-mounted inertial sensors: Comparing machine learning and strap-down integration methods

In this paper we implemented machine learning (ML) and strap-down integration (SDI) methods and analyzed them for their capability of estimating stride-by-stride walking speed. Walking speed was computed by dividing estimated stride length by stride time using data from a foot mounted inertial measurement unit. In SDI methods stride-by-stride walking speed estimation was driven by detecting gait events using a hidden Markov model (HMM) based method (HMM-based SDI); alternatively, a threshold-based gait event detector was investigated (threshold-based SDI). In the ML method a linear regression model was developed for stride length estimation. Whereas the gait event detectors were a priori fixed without training, the regression model was validated with leave-one-subject-out cross-validation. A subject-specific regression model calibration was also implemented to personalize the ML method.Healthy adults performed over-ground walking trials at natural, slower-than-natural and faster-than-natural speeds. The ML method achieved a root mean square estimation error of 2.0% and 4.2%, with and without personalization, against 2.0% and 3.1% by HMM-based SDI and threshold-based SDI. In spite that the results achieved by the two approaches were similar, the ML method, as compared with SDI methods, presented lower intra-subject variability and higher inter-subject variability, which was reduced by personalization.     

Power spectrum analysis of human femoral rotations during gait

Femoral rotational waveforms sampled at 15 Hz for a duration 20 s satisfy the sampling rate and frequency resolution requirements of such waveforms during walking. Spectral analysis provides a unique signature of the frequency composition of such signals. This identity may prove useful in characterising human gait and could be of value in future studies of walking in health and disease.     

Immediate effects of a controllable knee ankle foot orthosis for functional compensation of gait in patients with proximal leg weakness

Application of intermittent control of the knee joint stiffness in a knee ankle foot orthosis (KAFO) during gait is proposed. The approach combines inertial sensors and an actuator system in order to apply compensation in quadriceps weakness with a wearable device. Two methods, segment-angular rotation based and segment-angular velocity based, are analysed for the control of the knee joint state (intermittent stiffness) based on the inertial sensors signals. Protocolled tests are developed with two post-polio syndrome patients (PPS). In this study, the cases of gait with free-swinging leg and safe stance with the orthotic system are presented in terms of quantified kinematics (average peak angle of knee flexion of 50°) and evidences of reduction of frequent compensations (e.g. leg lateral movement) in post-polio syndrome patients. The results from immediate inspection indicate an important improvement of the gait patterns in two patients with proximal leg weakness by means of compensations applied by the wearable orthosis.     

Clinical meaning of the torque between stance leg and ground for the analysis of gait mechanism

Summary Transversal torque between the stance leg and the ground was measured in 169 test persons with normal gait (91 women, 78 men; ages 15–79 years) using three-dimensional force plates. Taking the average of six to ten single steps produces reproducible person- and group-specific data. This permits the isolation and study of individual solutions to specific problems of locomotion, so-called gait mechanisms. The relatively great torque during the double-stance phase is caused mainly by the medially directed, short-term impact peak at heel strike, with the stride length as lever arm. Double-stance torque is therefore determined by motion dynamics and does not help in understanding individual gait mechanisms. Torque measured during the single-stance phase is, in comparison, rather small and is interindividually relatively variable. Experimentally measured torque is considered in terms of various hypotheses concerning the creation of torque in the human gait. Men obviously tend, for reasons of equilibrium and stability, to compensate the various torques. Better than the more known vertical, sagittal, and frontal force components, the remaining torque represents the individual problem solution and therefore permits the study of specific gait mechanisms, both physiological and pathological. Using the characteristic gait of patients with hemiplegia as an example, it is shown that pathological torque observed systematically on the nonaffected side in such patients is a quantitative measure of the trunk rotation necessary to move the plegic side forward. Measurement of this torque therefore permits precise determination of the degree of damage, as well as quantitative control and objective documentation of the rehabilitation progress.Dedicated to Prof. Dr. N. Zöllner on the occasion of his 70th birthday     

A vision based proposal for classification of normal and abnormal gait using RGB camera

Human gait is mainly related to the foot and leg movements but, obviously, the entire motor system of the human body is involved. We hypothesise that movement parameters such as dynamic balance, movement harmony of each body element (arms, head, thorax…) could enable us to finely characterise gait singularities to pinpoint potential diseases or abnormalities in advance. Since this paper deals with the preliminary problem pertaining to the classification of normal and abnormal gait, our study will revolve around the lower part of the body. Our proposal presents a functional specification of gait in which only observational kinematic aspects are discussed. The resultant specification will confidently be open enough to be applied to a variety of gait analysis problems encountered in areas connected to rehabilitation, sports, children’s motor skills, and so on. To carry out our functional specification, we develop an extraction system through which we analyse image sequences to identify gait features. Our prototype not only readily lets us determine the dynamic parameters (heel strike, toe off, stride length and time) and some skeleton joints but also satisfactorily supplies us with a proper distinction between normal and abnormal gait. We have performed experiments on a dataset of 30 samples.     

Open source platform for collaborative construction of wearable sensor datasets for human motion analysis and an application for gait analysis

Nearly every practical improvement in modeling human motion is well founded in a properly designed collection of data or datasets. These datasets must be made publicly available for the community could validate and accept them. It is reasonable to concede that a collective, guided enterprise could serve to devise solid and substantial datasets, as a result of a collaborative effort, in the same sense as the open software community does. In this way datasets could be complemented, extended and expanded in size with, for example, more individuals, samples and human actions. For this to be possible some commitments must be made by the collaborators, being one of them sharing the same data acquisition platform.In this paper, we offer an affordable open source hardware and software platform based on inertial wearable sensors in a way that several groups could cooperate in the construction of datasets through common software suitable for collaboration. Some experimental results about the throughput of the overall system are reported showing the feasibility of acquiring data from up to 6 sensors with a sampling frequency no less than 118 Hz. Also, a proof-of-concept dataset is provided comprising sampled data from 12 subjects suitable for gait analysis.     

胫骨高位双平面上行截骨与下行截骨治疗内翻型膝关节骨性关节炎效果及步态分析

目的 探讨胫骨高位双平面上行截骨与下行截骨治疗内翻型膝关节骨性关节炎的效果及步态分析.方法 遴选出2017年1月至2019年6月因内翻型膝关节骨性关节炎住院患者32例,按手术方式分为胫骨高位双平面上行截骨组和下行截骨组,以观察两组患者的膝关节HSS评分、VAS评分、胫股角(FTA)、胫骨后倾角、Insall-Salva...     

第四代Oxford单髁置换术对膝关节内侧间室骨关节炎患者的疗效评估及步态分析

目的探讨第四代Oxford单髁置换术对膝关节内侧间室骨关节炎患者的临床疗效及对患者步态恢复的影响。方法将2016年1月至2018年1月收治并符合标准的30例(30膝)膝关节内侧间室骨关节炎患者纳入研究并作为试验组,另外再纳入20例(20膝)膝关节正常的志愿者作为本研究的正常组。试验组患者接受第四代Oxford单髁置换术,正常组研究对象不做任何治疗干预,仅作为观测指标对照。本研究观测指标主要包括疼痛视觉模拟评分(VAS评分)、膝关节学会评分系统(KSS)、美国WOMAC骨关节炎指数评分、美国特种外科医院膝关节评分(HSS评分)和步态分析运动学参数。比较试验组在术前、术后6个月及术后12个月的观测指标的差异,并分别与正常组作比较。结果试验组患者术前、术后6个月及术后12个月3个时间段两两之间的VAS评分、HSS评分、WOMAC评分以及KSS评分比较,差异均具有统计学意义(0.05)。试验组患者术前、术后6个月及术后12个月的步态分析各运动学参数的差异均具有统计学意义(0.05)。其中除最大前位移和最大内位移在术后6个月及术后12个月两个时间段差异无统计学意义之外,其他步态分析各运动学参数在3个时间段两两之间差异均具有统计学意义(0.05);试验组患者在术后12个月与正常组步态分析各运动学参数相比,最大伸直角、最大内位移和最大外位移比较,差异无统计学意义(0.05),但其余各步态分析各运动学参数差异仍然存在统计学意义(0.05)。结论在选择适当的病例和严格掌握手术适应证的前提下,第四代Oxford单髁置换术对膝关节内侧间室骨关节炎患者的近、中期疗效满意,术后患者关节功能更接近生理状态。     

Spatial synchronization of an insole pressure distribution system with a 3D motion analysis system for center of pressure measurements

Insole pressure systems are often more appropriate than force platforms for analysing center of pressure (CoP) as they are more flexible in use and indicate the position of the CoP that characterizes the contact foot/shoe during gait with shoes. However, these systems are typically not synchronized with 3D motion analysis systems. The present paper proposes a direct method that does not require a force platform for synchronizing an insole pressure system with a 3D motion analysis system. The distance separating 24 different CoPs measured optically and their equivalents measured by the insoles and transformed in the global coordinate system did not exceed 2 mm, confirming the suitability of the method proposed. Additionally, during static single limb stance, distances smaller than 7 mm and correlations higher than 0.94 were found between CoP trajectories measured with insoles and force platforms. Similar measurements were performed during gait to illustrate the characteristics of the CoP measured with each system. The distance separating the two CoPs was below 19 mm and the coefficient of correlation above 0.86. The proposed method offers the possibility to conduct new experiments, such as the investigation of proprioception in climbing stairs or in the presence of obstacles.     

Computer-assisted method for the analysis of postprandial gastrointestinal motility in conscious dogs

A fully automated system to quantify different parameters of gastrointestinal motility and gastroduodenal co-ordination in conscious dogs was designed and built around a personal technical computer (HP 9816). Online it performs sampling of contractions on four different sites of the digestive tract for two dogs simultaneously, data reduction, drift correction and storage of data on hard disk. Offine it performs baseline determination, peak detection, calculation of motility parameters such as amplitude and interval, plus co-ordination between gastric and duodenal motility and presentation of the results in both tabular and graphic form. To illustrate the possibilities and advantages of the computer analysis the early postprandial motor patterns for antrum, duodenum and jejunum were quantified during the first hour after administration of a small test meal.     

Usefulness of gait parameters obtained from inertial sensors attached to the lower trunk and foot for assessment of gait performance in the early postoperative period after total knee arthroplasty

BackgroundThis study was performed to (i) compare gait parameters obtained from inertial sensors attached to the lower trunk and foot between patients in the early postoperative period after total knee arthroplasty (TKA) and healthy age- and sex-matched controls and (ii) elucidate the association between the gait parameters and patient-reported outcome measures (PROMs).MethodThe gait performance of 19 patients who had undergone TKA was assessed using inertial sensors and PROMs obtained from the Knee Injury and Osteoarthritis Outcome Score (KOOS) 1 week before hospital discharge. The patients walked along a 15-m walkway and we calculated the following gait parameters: walking speed, coefficient of variation (CV) of stride time, unbiased autocorrelation coefficient (AC), harmonic ratio (HR), and symmetry index (SI). The same gait parameter data from 19 age- and sex-matched healthy adults (controls) were obtained from our past study.ResultsThe TKA group demonstrated slower walking speed, larger CV of stride time, lower HR in all three directions, lower AC in the vertical direction, and higher SI in the vertical direction than the healthy control group (all p < 0.05). Correlation analysis revealed that the SI in the anteroposterior direction was significantly correlated with the KOOS symptoms subscore and ADL subscore (p < 0.05).ConclusionsPatients in the early postoperative period after TKA exhibited worse gait performance as assessed by inertial sensors compared with healthy controls. Gait symmetry was correlated with PROMs. These results indicate the usefulness of assessing gait parameters after TKA.     

Peak discrimination as a method for quantitative evaluation of neural activity by computer

A computer method (PDP-12) for the quantification of neural activity in single- as well as few-fibre preparations of nerves was devised and tested on function-generator signals and on neurograms from baro- and chemoreceptor fibres of the carotid sinus nerve of rabbits. The principle of the program was to search continuously for maxima and minima of the electrogram regardless of the absolute voltage range in which they occurred. Action potentials were then distinguished from noise by comparing these maxima with amplitude discriminators. The latter were derived from the previous analysis of noise in selected neurograms and in recordings during activity-free intervals of the normal electrogram or temporary cold block of the preparation. From peaks accepted as action potentials the program computed total mean frequency, amplitude histogram and interval histogram as standard outputs. The method permitted one to determine in few-fibre preparations not only total activity but also response characteristics of different fibre components. However, owing to principal limitations shown to be inherent in such techniques, the exact quantification of neurograms from several fibres became impossible if the mean frequency—depending on the type of activity—exceeded several hundred to about 1000 impulses/s. By systematic variation of program parameters and type and rate of neural activity, the performance characteristics of the program as well as certain general properties of single-, few- and multi-fibre neurograms were evaluated.     

A simple method for censored age-of-onset data subject to recall bias: Mothers' reports of age of puberty in male twins

Genetic analysis of variation in age of onset of development milestones or psychopathological behaviors has been little researched, owing largely to the computational difficulty of dealing with censored observations. Censored observations arise when the only information on individuals is that they have reached a particular age but without onset having occurred. This paper shows how models can be simply fitted to such data using programs that can perform genetic analysis of categorical data by maximum likelihood. The method is illustrated using the program Mx with data on maternal report of the onset of puberty in twin sons from the Virginia Twin Study of Adolescent Behavioral Development. Frequently, data on age of onset is collected by retrospective recall. This can pose a variety of measurement problems. Suggestions are made for models that account for some of these problems or are robust to their presence. Substantial evidence for telescoping of onset dates is found for the puberty data. If left unaccounted for, these effects can artifactually inflate estimates of common environment effects.     

New approach to vital analysis of functional activity in ABC transporters (markers for multidrug resistance) in solid tumors by the method of flow cytofluorometry

We developed and described a new approach to vital analysis of functional activity of multidrug resistance markers (ABC transporters) in intact biopsy specimens from human solid tumors by the method of flow cytofluorometry. The algorithm of the study underwent revision, and the cell suspension was obtained in the final stage. Intensification of intracellular doxorubicin accumulation (fluorescence) and increase in the number of fluorescent cells and total fluorescence of doxorubicin-accumulating cells produced by ABC transporter inhibitor sodium azide served as the criteria of expression of these transporters in tumor tissue. Informative value of changes in various parameters of doxorubicin fluorescence is discussed. The increase in the count of fluorescent cells in the suspension of tumors cells after treatment with the inhibitor indicates the presence of tumor cells absolutely resistant to this preparation. The proposed method is technically simple, suitable for structurally different tumors, requires small amounts of the biopsy material and, therefore, can be used for routine analysis. The results of our analysis and spectrofluorometric assay of ABC transporters agree very closely, which suggest that this method is adequate for the purpose.     

New method for the analysis of multiple positron emission tomography dynamic datasets: an example applied to the estimation of the cerebral metabolic rate of oxygen

Positron emission tomography (PET) provides the ability to extract useful quantitative information not available through other radiological techniques. In certain studies, the physiological parameters of interest cannot be determined from the data obtained from a single PET experiment alone. In this case, multiple experiments are required. At present, the methods used to analyse measurements acquired from multiple experiments often involve considering them separately during the modelling procedures. These methods of analysis may cause errors to be propagated through successive modelling procedures and do not fully utilise the information content provided by the PET measurements. A new method is presented, based on linear least squares for the analysis of PET dynamic data acquired from multiple experiments. This method simultaneously considers the complete set of measurements obtained and provides reliable parameter estimates. The efficient use of the information content provided by multiple experiments is considered and the propagation of errors is discussed. To facilitate our discussion, we apply this new method to the estimation of the cerebral metabolic rate of oxygen and the parameters of the oxygen utilisation model as a practical example. The results demonstrate a significant improvement in the reliability and estimation accuracy of the estimates for this new method. Furthermore, this method reduced the likelihood of errors being propagated. Therefore, the proposed method is suitable for the analysis of multiple PET dynamic datasets.