Walking In Healthy Subjects Research Articles

Simplified Markerless Stride Detection Pipeline (sMaSDP) for Surface EMG Segmentation.

To diagnose mobility impairments and select appropriate physiotherapy, gait assessment studies are often recommended. These studies are usually conducted in confined clinical settings, which may feel foreign to a subject and affect their motivation, coordination, and overall mobility. Conducting gait studies in unconstrained natural settings instead, such as the subject's Activities of Daily Life (ADL), could provide a more accurate assessment. To appropriately diagnose gait deficiencies, muscle activity should be recorded in parallel with typical kinematic studies. To achieve this, Electromyography (EMG) and kinematic are collected synchronously. Our protocol sMaSDP introduces a simplified markerless gait event detection pipeline for the segmentation of EMG signals via Inertial Measurement Unit (IMU) data, based on a publicly available dataset. This methodology intends to provide a simple, detailed sequence of processing steps for gait event detection via IMU and EMG, and serves as tutorial for beginners in unconstrained gait assessment studies. In an unconstrained gait experiment, 10 healthy subjects walk through a course designed to mimic everyday walking, with their kinematic and EMG data recorded, for a total of 20 trials. Five different walking modalities, such as level walking, ramp up/down, and staircase up/down are included. By segmenting and filtering the data, we generate an algorithm that detects heel-strike events, using a single IMU, and isolates EMG activity of gait cycles. Applicable to different datasets, sMaSDP was tested in healthy gait and gait data of Parkinson's Disease (PD) patients. Using sMaSDP, we extracted muscle activity in healthy walking and identified heel-strike events in PD patient data. The algorithm parameters, such as expected velocity and cadence, are adjustable and can further improve the detection accuracy, and our emphasis on the wearable technologies makes this solution ideal for ADL gait studies.

The dynamic sagittal balance: Definition of dynamic spino-pelvic parameters using a method based on gait analysis

IntroductionEvaluation of sagittal balance parameters is a standard assessment before spine surgery. However, these parameters can change during walking. We aimed to describe the behavior of spino-pelvic parameters during walking in healthy subjects. Material and methodsAnalyses were performed in 60 healthy subjects. Static spinal sagittal balance parameters were assessed. We performed gait analysis and we used SMART-DX 500® to analyze parameters aimed at defining dynamic sagittal balance, including pelvic tilt angle (PTA), sagittal trunk shift (STS), and trunk angle (TA). We considered rotational and obliquity movements of the pelvis, flexo-extension movements of the hip, trunk, and knees. Analyses were performed in a standing posture and during walking. ResultsPTA-cycle, PTA-stance, PTA-swing, STS-cycle, STS-stance, and STS-swing showed good-to-excellent internal reliability (ICC = 0.867; ICC = 0.700; ICC = 0.817, respectively). The parameters with the lowest variability were radiographic PI (CV = 16.53%), PTA-stance (CV = 9.55%), and PTA-swing (CV = 17.22%). PT was directly related to PTA-cycle (r = 0.534, p = .027). PI was inversely correlated with trunk flexo-extension range of motion (r = −0.654, p = .004) and dynamic PT (r = −0.489, p = .047). LL and SS were directly related to knee flexo-extension (r = 0.505, p = .039; r = 0.493, p = .045, respectively). SVA was correlated with the trunk obliquity in dynamics (r = 0.529, p = .029). PTA-cycle was directly related to trunk obliquity (r = 0.538, p = .049). STS and TA in the three phases of step were related to the kinematic parameters of the pelvis. TA was related to flexo-extension of the hip and knee. ConclusionsVariations of dynamic spino-pelvic parameters occur during walking and modify sagittal balance from a static to a dynamic condition.

Motor control of the lower limbs while walking with the TWIN exoskeleton operated by TWINActa in healthy subjects

Lower limb exoskeletons are medical devices used in the rehabilitation to provide physical therapy to individuals with neurological disorders [1]. These robotic devices were originally designed and developed for spinal cord injury subjects, who do not have any residual walking abilities, and are therefore mainly based on an assistive approach. To successfully use these machines in subjects with residual capacities such as persons post stroke, the control system must be adapted to an assist-as- needed control scheme. This approach requires the subject active participation to stimulate the voluntary muscle contraction of the paretic limb and manage the somatosensory feedbacks subsequent to the action. For these reasons, we have developed TWINActa, a control suite for gait training following stroke, that provide asymmetric assistance to the user. The assistance-as-needed can be provided in the following modes: (i) support during the toe-off phase of the non-paretic leg; (ii) pelvic tilt damping during stance phase; (iii) stabilization of the knee joint of the supporting leg during the double support phases; and (iv) hip extension support of paretic leg during the stance phase. This study was aimed at verifying if motor control during a walking task performed with an exoskeleton, operated by TwinActa, is similar to the physiological control of walking in healthy subjects. Five healthy volunteers were asked to perform motor tasks (i.e., overground walking, stairs ascending and stair descending) wearing the TWIN exoskeleton [2] operated by TWINActa control system. During the task EMG signals were acquired from 12 muscles (10 placed on the lower limb and 2 on the upper limbs per side) and movement data were recorded from 2 IMUs placed on the shanks. Non-negative matrix factorization was carried out on the EMG recorded signal to identify muscle synergies [3]. The EMG activity patterns were also mapped onto the rostro-caudal location of ipsilateral motoneurons pools in the human spinal cord [4]. Based on the Kendall myotomal charts of segmental localization [5], we reconstructed the sacral (S1-S2) and lumbard (L2-L5) motor pool activation profiles. Pearson's correlation coefficient was used to evaluate the similarity degree of 1) muscle synergies and 2) sacral and lumbar motor pool activation profiles of walking with exoskeleton with respect to the normative reference (without device) provided by Eurobench project (Pepato scenario). Four muscle synergies accounted for a R2 > 0.85 for all participants during overground walking. A strong degree of similarity (correlation) of activation of sacral and lumbar motor pools with respect to the reference group was found (mean ± SD, 0.77 ± 0.06 and 0.78 ± 0.11, for sacral and lumbar spinal output respectively). Also the mean similarly of the muscle synergies activation profiles was strong (mean ± SD, 0.70 ± 0.14) with respect to the four physiological muscle synergies involved in gait control [6]. The four muscle synergies involved in the gait control [6] were found while walking with the exoskeleton operated by TWINActa in neurologically intact subjects. We found also a strong degree of similarity between the motor pools wearing the exoskeleton with respect to the normative reference of walking without the device. Since the spinal motor pools are associated with functional grouping of motoneurons of the lower limb muscles, our findings suggest that the Twin exoskeleton operated by TWINActa can be used as rehabilitation device to enhance the recovery of the physiological motor control in persons with residual ability. Further studies need to be conducted to verify this finding in subjects with neurological diseases.

Design of an experimental platform of gait analysis with ActiSense and StereoPi

Abstract Gait analysis is a systematic study of human movement. Combining wearable foot pressure sensors and machine learning (ML) solutions for a high-fidelity body pose tracking from RGB video frames could reveal more insights into gait abnormalities. However, accurate detection of heel strike (HS) and toe-off (TO) events is crucial to compute interpretable gait parameters. In this work, we present an experimental platform to study the timing of gait events using a new wearable foot pressure sensor (ActiSense System, IEE S.A., Luxembourg), and Google’s open-source ML solution MediaPipe Pose. For this purpose, two StereoPi systems were built to capture stereoscopic videos and images in real time. MediaPipe Pose was applied to the synchronized StereoPi cameras, and two algorithms (ALs) were developed to detect HS and TO events for gait and analysis. Preliminary results from a healthy subject walking on a treadmill show a mean relative deviation across all time spans of less than 4% for the ActiSense device and less than 16% for AL2 (33% for AL1) employing MediaPipe Pose on StereoPi videos. Finally, this work offers a platform for the development of sensor- and video-based ALs to automatically identify the timing of gait events in healthy individuals and those with gait disorders.

Kinematic Evaluation of the Sagittal Posture during Walking in Healthy Subjects by 3D Motion Analysis Using DB-Total Protocol.

Posture can be evaluated by clinical and instrumental methods. Three-dimensional motion analysis is the gold standard for the static and dynamic postural assessment. Conventional stereophotogrammetric protocols are used to assess the posture of pelvis, hip, knee, ankle, trunk (considered as a single segment) and rarely head and upper limbs during walking. A few studies also analyzed the multi-segmental trunk and whole-body kinematics. Aim of our study was to evaluate the sagittal spine and the whole-body during walking in healthy subjects by 3D motion analysis using a new marker set. Fourteen healthy subjects were assessed by 3D-Stereophotogrammetry using the DB-Total protocol. Excursion Range, Absolute Excursion Range, Average, intra-subject Coefficient of Variation (CV) and inter-subject Standard Deviation Average (SD Average) of eighteen new kinematic parameters related to sagittal spine and whole-body posture were calculated. The analysis of the DB-Total parameters showed a high intra-subject (CV < 50%) and a high inter-subject (SD Average < 1) repeatability for the most of them. Kinematic curves and new additional values were reported. The present study introduced new postural values characterizing the sagittal spinal and whole-body alignment of healthy subjects during walking. DB-Total parameters may be useful for understanding multi-segmental body biomechanics and as a benchmark for pathological patterns.

A 3-Dimensional Gait Analysis of the Effects of Fatigue-Induced Reduced Foot Adductor Muscle Strength on the Walking of Healthy Subjects.

Dysfunction of the tibialis posterior muscle is the most common cause of adult acquired flat foot. Tibialis posterior muscle weakness has been observed in several patient populations, including those in the early stages of rheumatoid arthritis. However, the influence of tibialis posterior weakness on gait mechanics is not fully understood, although gait instability has been reported. In 24 healthy participants, 3-dimension lower limb kinematics and kinetics during walking were evaluated bilaterally, before and after, a muscle fatigue protocol aiming to decrease the right foot adductor muscles strength, including the tibialis posterior muscle. The 3-dimension gait kinematics and kinetics were analyzed with statistical parametric mapping. The stance phase duration was increased for the right side. The right ankle external rotation moment decreased, and the left hip extension moment increased with reduced muscle strength compared with normal strength conditions. These changes are similar in patients with dysfunction in the tibialis posterior muscle, indicating that compensatory strategies observed in these patients might be related to the loss of tibialis posterior muscle strength. Such strategies may involve the unaffected side.

The Accuracy and Precision of Gait Spatio-Temporal Parameters Extracted from an Instrumented Sock during Treadmill and Overground Walking in Healthy Subjects and Patients with a Foot Impairment Secondary to Psoriatic Arthritis.

The objectives of this study were to assess the accuracy and precision of a system combining an IMU-instrumented sock and a validated algorithm for the estimation of the spatio-temporal parameters of gait. A total of 25 healthy participants (HP) and 21 patients with foot impairments secondary to psoriatic arthritis (PsA) performed treadmill walking at three different speeds and overground walking at a comfortable speed. HP performed the assessment over two sessions. The proposed system’s estimations of cadence (CAD), gait cycle duration (GCD), gait speed (GS), and stride length (SL) obtained for treadmill walking were validated versus those estimated with a motion capture system. The system was also compared with a well-established multi-IMU-based system for treadmill and overground walking. The results showed a good agreement between the motion capture system and the IMU-instrumented sock in estimating the spatio-temporal parameters during the treadmill walking at normal and fast speeds for both HP and PsA participants. The accuracy of GS and SL obtained from the IMU-instrumented sock was better compared to the established multi-IMU-based system in both groups. The precision (inter-session reliability) of the gait parameter estimations obtained from the IMU-instrumented sock was good to excellent for overground walking and treadmill walking at fast speeds, but moderate-to-good for slow and normal treadmill walking. The proposed IMU-instrumented sock offers a novel form factor addressing the wearability issues of IMUs and could potentially be used to measure spatio-temporal parameters under clinical conditions and free-living conditions.

User-driven treadmill walking promotes healthy step width after stroke

BackgroundWalking with user-driven treadmill control is believed to be more like overground walking than fixed-speed treadmill walking. Walking speed and ground reaction forces differ between overground and fixed-speed treadmill walking, but not between overground and user-driven treadmill walking in healthy and post-stroke subjects. However, studies assessing spatiotemporal gait parameters during user-driven treadmill walking are limited. This information may help confirm that user-driven treadmill walking is more like overground walking than fixed-speed treadmill walking, as well as inform the development of post-stroke gait rehabilitation programs. Research questionHow do spatiotemporal gait parameters for individuals post-stroke differ between fixed-speed and user-driven treadmill walking? MethodsEighteen subjects (10 M, 8 F; 62 ± 12 years; 1.73 ± 0.12 m; 84.9 ± 12.9 kg; 40 ± 30 months post-stroke) with chronic post-stroke hemiparesis participated in this study. Participants walked on an instrumented treadmill in its fixed-speed and user-driven modes at their self-selected and fastest comfortable walking speeds. Subjects wore retroreflective markers for motion capture. Shapiro-Wilk tests were used to assess for normality and one-way repeated measures ANOVAs were used to compare between conditions with α = 0.05. Bonferroni corrections were used for multiple comparisons. ResultsStep width was significantly smaller with user-driven control (13.7 cm, 95 % CI: [0.131, 0.145]) than fixed-speed control (16.8 cm, 95 % CI:[0.160, 0.174]), while step length and step time did not differ across treadmill conditions. Step length and step time differed between self-selected and fast walking speeds, but not treadmill control conditions. SignificanceThe results of this study show that user-driven treadmill control encourages healthy gait biomechanics and a greater sense of stability in post-stroke subjects. Individuals post-stroke walked with smaller step width with user-driven treadmill control, which has been associated with increased balance. Post-stroke gait rehabilitation may benefit from programs with user-driven treadmill training paradigms to improve mobility following stroke.

Effect of ankle joint fixation on tibialis anterior muscle activity during split-belt treadmill walking in healthy subjects: A pilot study

Effect of ankle joint fixation on tibialis anterior muscle activity during split-belt treadmill walking in healthy subjects: A pilot study

Effect of ankle joint fixation on tibialis anterior muscle activity during split-belt treadmill walking in healthy subjects: A pilot study.

Objectives This study aims to examine the characteristics of muscle activity change of the tibialis anterior (TA) muscle in healthy adults while they walked on a split-belt treadmill with one fixed ankle. Patients and methods This randomized controlled trial was conducted between November 2017 and July 2018. Fourteen healthy male individuals (mean age 31.4 years; range, 23 to 50 years) were divided into two groups: right ankle joint fixed by ankle-foot orthosis (fixation group) and no orthosis (control group). Both groups were asked to walk on a treadmill with the same belt speed. After familiarizing with walking on both belts at 5.0 km/h, they walked for 6 min with the right belt slower (2.5 km/h) and the left faster (5.0 km/h). For analysis, the 6 min were divided equally among three time periods. The TA muscle activity was calculated at first and last time periods. We compared muscle activities in time periods (early and late phase) and in groups (fixation and control) using two-way mixed analysis of variance. Results The TA muscle activity decreased in the late phase regardless of ankle joint fixation, and also decreased in the fixation group regardless of the time periods. There was an interaction between these factors. Conclusion These data show that changes in the TA muscle activity were smaller in the fixation group, suggesting that the ankle joint fixation reduces the adaptation.

Generation of a gait pattern for a lower limb rehabilitation exoskeleton

In this article, a simple prototype and control system of a lower limb exoskeleton driven by stepper motors was proposed. To study kinematic parameters of the device, a general, three-dimensional simulation model of the exoskeleton was developed. Moreover, a gait pattern was modeled for hip, knee, and ankle joints. It represents sagittal plane angular positions of joints during normal gait and consists of three piecewise-defined sine-square-based functions. It is based on the experimental gait data recorded with an optoelectronic motion capture system for a healthy subject walking on a treadmill. Although the developed pattern is intended to be implemented in a control system of a lower limb exoskeleton for gait rehabilitation, it can be used to control bipedal robots as well. Last but not least, the control approach was tested with the exoskeleton prototype.

Comparison of different optimal control formulations for generating dynamically consistent crutch walking simulations using a torque-driven model

Walking impairment due to spinal cord injury can be improved using active orthoses, together with some type of external support such as crutches for balance. This study explores how optimal control problem formulation affects the ability to generate dynamically consistent crutch walking simulations with active orthosis assistance that closely reproduce experimental data. The investigation compares eight optimal tracking problem formulations using a torque-driven full-body skeletal model of a healthy subject walking with active knee-ankle-foot orthoses and forearm crutches. We have found that small adjustments to ground reactions are required to achieve convergence, tracking of joint instead of marker coordinates significantly improves convergence, and minimising joint jerks instead of joint accelerations has only a minor effect on the problem convergence. These results provide guidance for future work that seeks to develop predictive optimal control simulations that can identify orthosis control parameters that maximise improvement in walking function on an individual patient basis.

Dispersion of knee helical axes during walking in young and elderly healthy subjects

Knee joint rotation center displacement can be estimated in vivo through the analysis of helical axis (HAs) dispersion. HAs can be analyzed during walking, providing information on joint stability. The study aim was to describe knee HAs dispersion during walking in dominant and non-dominant legs of young and elderly healthy subjects.Twenty young (YG: age 23.3 ± 2.4 years) and twenty elderly (EG: age 69.3 ± 4.6 years) healthy subjects were asked to walk on a treadmill at a self-selected speed with reflective markers placed bilaterally on thighs and shanks to detect HAs dispersion and knee kinematics with an optoelectronic system. HAs dispersion was described during the following four phases of gait cycle: (1) flexion from 95% of the previous gait cycle to 10% of the subsequent gait cycle, (2) extension from 10% to 40%, (3) flexion from 40% to 75% and (4) extension from 75% to 95% of the gait cycle. Mean Distance (MD) and Mean Angle (MA) were used as HAs dispersion indexes during each gait phase.Participants showed greater MD and MA in sagittal and frontal planes during the first and second phases. EG revealed higher MD (p = 0.001) and MA (p < 0.001) during the first phase and higher MA (p = 0.001) during the fourth phase in both dominant and non-dominant legs on the sagittal plane.HAs dispersion could be related to the amount of forces acting on knee (first two phases) and knee degeneration (elderly). These results may be used as reference data in further studies on HAs dispersion in presence of knee pathologies or after knee surgery or rehabilitation.

Measures of dynamic balance during level walking in healthy adult subjects: Relationship with age, anthropometry and spatio-temporal gait parameters.

The maintenance of balance in dynamic conditions (e.g. during walking) is a necessary requirement that motor control must reach to avoid falls. However, this is a challenging situation, since to ensure the forward progression of the body, the center of mass must stay outside the base of support in the sagittal plane, and simultaneously remain inside the lateral borders in the frontal plane. Deviation from normative data of healthy subjects in dynamic balance could be used to quantify gait stability, fall risk and to provide hints for rehabilitation. However, normative data can be influenced by age, sex, anthropometry and spatio-temporal gait parameters, and such differences among subjects and leg side can hamper accurate assessment. The aims of this study were to investigate, in a group of healthy subjects: (1) possible asymmetry in dynamic balance maintenance strategies between leg sides, (2) the influence of age, sex and anthropometry on stability and (3) its dependence by spatio-temporal gait parameters. A total of 34 healthy subjects aged between 21 and 71 years, and ranging from 50.1 to 101.6 kg of body mass and from 155.0 to 188.9 cm of height were assessed on spatio-temporal and dynamic balance parameters (Foot Placement Estimator at heel strike and Margin of Stability at mid-stance) during self-selected gait. No parameter showed differences between legs. Dynamic balance parameters were influenced by sex, age, body mass and height mainly in the frontal plane. These measures were also correlated with gait speed and stride length both in the antero-posterior and medio-lateral directions. In addition also cadence and step width influenced the stability in the sagittal and frontal planes, respectively. The findings of this study confirm the symmetry in motor control of dynamic balance during self-selected gait in healthy subjects. Sex, anthropometry and spatio-temporal gait parameters have a significant effect on stability parameters, and this should be taken into account in dynamic balance studies.

Effect of ankle-foot orthosis on level walking in healthy subjects.

An ankle-foot orthosis is often prescribed in the rehabilitation of patients with neurological motor disorders such as hemiparesis. However, walking with a unilateral ankle-foot orthosis may not be effectively achieved just by trying to reproduce normal intact walking with a symmetrical gait pattern. Understanding skills to facilitate walking gait with a unilateral ankle-foot orthosis has implications for better rehabilitative interventions to help restore walking ability in patients with stroke. We, therefore, analyzed the kinematics and ground reaction forces of walking with and without an ankle-foot orthosis in healthy subjects to infer the possible skills to facilitate walking gait with a unilateral ankle-foot orthosis. Adult male participants were asked to walk with and without an ankle-foot orthosis across two force platforms set in a wooden walkway, and body kinematics and ground reaction force profiles in the sagittal plane were simultaneously recorded. We found that the forward tilting angle of the trunk at the time of toe-off of the leg with the ankle-foot orthosis was significantly larger than that of the leg without the ankle-foot orthosis, to adaptively compensate for the loss of ankle joint mobility due to the unilateral ankle-foot orthosis. Furthermore, the peak vertical ground reaction force at heel-contact was significantly larger in the leg without the ankle-foot orthosis than in the leg with the ankle-foot orthosis owing to the fact that the stance phase duration of the leg with the ankle-foot orthosis was relatively shorter. Such information may potentially be applied to facilitate walking training in stroke patients wearing a unilateral ankle-foot orthosis.

Admittance Shaping-Based Assistive Control of SEA-Driven Robotic Hip Exoskeleton

This paper presents an admittance shaping-based assistive control for a series elastic actuator (SEA) driven robotic hip exoskeleton that can assist individuals with hip muscle weakness to restore normative mobility. The motivation for this paper is to develop a unified controller framework for designing an SEA-driven hip exoskeleton to assist walking and enhance gait stability. The controller design aims to modify the dynamic response of a coupled human-exoskeleton system, i.e., the relationship between the net muscle torque exerted by the human and the resulting angular motion, to ensure strong human-exoskeleton synergy to provide the effective assistance. This controller was preliminarily evaluated on a healthy subject walking on a treadmill at a speed of 1.0 m/s. Results showed that the exoskeleton can effectively provide walking assistance to the human by reducing electromyography (EMG) activation and increasing agility during locomotion. Specifically, EMG was reduced 3.3%–38% when walking with the hip exoskeleton when compared to walking without wearing the hip exoskeleton. In addition, timing of the maximum hip flexion angle increased by 10% (moved from 42% to 32% of gait cycle) when the controller had an inertia compensation of 60%. The faster onset of the maximum flexion angle will allow the wearer to more quickly generate reactive steps when trying to avoid a fall. Future work will aim to apply the hip exoskeleton to persons having hip muscle weakness or other musculoskeletal impairment, to restore hip movement and enough hip force to walk normally.

Immediate after-effects of robot-assisted gait with pelvic support or pelvic constraint on overground walking in healthy subjects

BackgroundRecovery of walking is a primary rehabilitation goal of most stroke survivors. Control of pelvic movements is one of the essential determinants of gait, yet surprisingly, conventional robot-assisted gait trainers constrain pelvic movements. Novel robot-assisted gait trainers, such as LOPES II, are able to support pelvic movements during gait. The aim of this cross-over study was to investigate the immediate after-effects of pelvic support (PS) or pelvic constraint (PC) gait training with LOPES II on overground walking in healthy subjects.MethodsThirteen able-bodied subjects (22.8 ± 2.1 years) participated in two 20-min gait training sessions with LOPES II; one with PS and one with PC. During the PS-training, the LOPES II actively guided the lateral displacement of the pelvis, while pelvic rotations were free. During the PC-condition, both lateral displacement and pelvic rotations were constrained and reduced to a minimum. The training sessions were separated by a 30-min resting period. Lateral displacement of the pelvis, hip and knee kinematics, and spatiotemporal parameters during overground walking were determined at baseline and immediately following the training using 3D gait analysis.ResultsDuring the PS-condition in LOPES II the lateral pelvic displacement was significantly greater (105.6 ± 0 .5 mm) than during the PC-condition (10.8 ± 0 .7 mm; p < 0.001). Analysis of the first five steps of overground walking immediately following PC-condition showed significantly smaller lateral displacements of the pelvis (32.3 ± 12.0 mm) compared to PS-condition (40.1 ± 9 .8 mm; p < 0.01). During the first five steps, step width was significantly smaller after PC-condition (0.17 ± 0. 04 m) compared to PS-condition (0.20 ± 0.04 m; p = 0.01) and baseline (0.19 ± 0. 03 m; p = 0.01). Lateral displacement of the pelvis and step width post training returned to baseline levels within 10 steps. PC- nor PS-condition affected kinematics, gait velocity, cadence, stride length or stance time.ConclusionsIn healthy subjects, robot-assisted gait training with pelvic constraint had immediate negative after-effects on the overground walking pattern, as compared to robot-assisted gait training with pelvic support. Gait training including support of the lateral displacement of the pelvis better resembles the natural gait pattern. It remains to be identified whether pelvic support during robot-assisted gait training is superior to pelvic constraint to promote gait recovery in individuals with neurological disorders.

Robust Active Disturbance Rejection Control via Control Lyapunov Functions: Application to Actuated-Ankle–Foot-Orthosis

In this paper, the problem of trajectory tracking, for an Actuated-Ankle–Foot-Orthosis(AAFO) to assist the gait of paretic patients, is addressed. The control strategy is based on the system’s flatness property, which allows the development of an Active Disturbance Rejection Control (ADRC). For this purpose, an Extended State Observer (ESO) is designed to estimate on-line the unknown disturbances and canceled by injecting the output of ESO into the feedback loop. A stability analysis of the estimation error dynamics is carried out in the Input-to State Stability (ISS) framework, stating the observer’s robustness. On the other hand, the feedback design is based on the existence of a Control Lyapunov Function (CLF) and the Sontag’s formula. The stability analysis discloses that the tracking trajectory controller is ISS, i.e. robustly stable. Finally, the effectiveness of the ADRC strategy is validated by performing real-time tests with a healthy subject walking on a treadmill at self-selected speed. The experimental results validate the theoretical analysis.

Control Strategy Based on Kinetic Motor Primitives for Lower Limbs Exoskeletons

In order to assist after-stroke individuals with hemiparetic gait pattern to rehabilitate their movements, many research centers have developed exoskeletons for lower limbs and control strategies for them. The present work aims to develop a robotic control strategy based on kinetic motor primitives capable of assisting the recovery of patients with compromised movements. The joint positions of a healthy subject walking on a treadmill, wearing and not wearing a six degree- of-freedom exoskeleton, were obtained through IMUs (Inertial Measurements Units) and used to calculate the joint torques using the OpenSim software. Motor primitives of the kinetic data (torques), and their respective weights, were then computed using Principal Component Analysis (PCA). Based on the ratio of the weights, a control strategy was designed to generate the necessary robot torque in order to assist the individual during the walking wearing the exoskeleton. The proposed strategy was evaluated with the subject wearing a torque-controlled orthosis for 120 seconds at 1.5 km/h on a treadmill. The torques and angles of the individual were obtained for posterior analysis.

Analysis of modifications of the plantar parameters after the use of a proprioceptive insole: regular gait.

The human foot is the basis of support and propulsion for gait and it provides support and flexibility for effective weight transfer. Therefore a correct distribution of loads and pressures on the surface of the foot is of fundamental importance to ensure a correct walking and maintaining balance in both static and dynamic conditions. The aim of our study was to evaluate the effects of innovative insoles, named regular gait (RG), on plantar pressures distribution during standing position and walking in healthy subjects; therefore, we investigated whether these effects are maintained after insole removing. Fifty subjects were tested; these were free of foot diseases or damage to the anatomical structures involved in the processes above posture. These subjects underwent rating scales and static and dynamic baropodometric examination before and after using RG. The results obtained shown that the RG, for as we have designed, are able to change the distribution of the parameters both in static and dynamic conditions. We have also shown that the best results were obtained only after a month of treatment with RG and that the results obtained persist even in the tests post-treatment without insoles. In conclusion, the data obtained in this study suggest that RG could be efficient in acting on parameters related to maintenance of upright posture and gait. This would allow the treated subjects to improve their posture both while walking and during the maintenance of the upright position.