Angle-angle diagrams in the assessment of locomotion in persons with multiple sclerosis: A preliminary study

Gait analysis is clinically relevant in persons with multiple sclerosis (PwMS) and consists of several joint angular displace-ment-time relationships and spatiotemporal parameters. However, it lacks representation by means of diagrams in which knee angle-hip angle and knee angle-ankle angle variations are plotted against each other at the same instants of time. Three-dimensional kinematic analysis was performed on 20 subjects (10 PwMS/10 healthy controls, HCs), and the knee-angle/hip-angle and knee-angle/ankle-angle diagrams of both lower limbs were determined in the sagittal plane while walking on a motorized treadmill. The area (a quantifier of conjoint range of motion) and the perimeter (a quantifier of coordina-tion) of angle-angle diagram loops were calculated. PwMS showed reduced knee-angle/ankle-angle loops compared to HCs (P<0.05, ES = 0.80), whereas the hip-angle/ankle-angle loops between the PwMS and HCs was not significant (P> 0.05). Similarly, the activation of leg muscles showed significant differences between PwMS and HCs (p ranged from 0.05-to 0.001; ES ranged from 1.30 to 1.89). The results indicate that the proposed knee-angle/hip-angle diagram is feasible and could be applied as a reliable tool in future studies aimed at assessing the acute and long-term effects of specific exercise programmes and/or pharmacological treatment in PwMS.

Validation of wearable inertial sensor-based gait analysis system for measurement of spatiotemporal parameters and lower extremity joint kinematics in sagittal plane

Wearable inertial sensor-based motion analysis systems are promising alternatives to standard camera-based motion capture systems for the measurement of gait parameters and joint kinematics. These wearable sensors, unlike camera-based gold standard systems, find usefulness in outdoor natural environment along with confined indoor laboratory-based environment due to miniature size and wireless data transmission. This study reports validation of our developed (i-Sens) wearable motion analysis system against standard motion capture system. Gait analysis was performed at self-selected speed on non-disabled volunteers in indoor ( n = 15) and outdoor ( n = 8) environments. Two i-Sens units were placed at the level of knee and hip along with passive markers (for indoor study only) for simultaneous 3D motion capture using a motion capture system. Mean absolute percentage error (MAPE) was computed for spatiotemporal parameters from the i-Sens system versus the motion capture system as a true reference. Mean and standard deviation of kinematic data for a gait cycle were plotted for both systems against normative data. Joint kinematics data were analyzed to compute the root mean squared error (RMSE) and Pearson’s correlation coefficient. Kinematic plots indicate a high degree of accuracy of the i-Sens system with the reference system. Excellent positive correlation was observed between the two systems in terms of hip and knee joint angles (Indoor: hip 3.98° ± 1.03°, knee 6.48° ± 1.91°, Outdoor: hip 3.94° ± 0.78°, knee 5.82° ± 0.99°) with low RMSE. Reliability characteristics (defined using standard statistical thresholds of MAPE) of stride length, cadence, walking speed in both outdoor and indoor environment were well within the “Good” category. The i-Sens system has emerged as a potentially cost-effective, valid, accurate, and reliable alternative to expensive, standard motion capture systems for gait analysis. Further clinical trials using the i-Sens system are warranted on participants across different age groups.

Upgrade of an integrated Langmuir probe system on the closed divertor target plates in the HL-2A tokamak

A newly designed divertor Langmuir probe diagnostic system has been installed in a rare closed divertor of the HL-2A tokamak and steadily operated for the study of divertor physics involved edge-localized mode (ELM) mitigation, detachment and redistribution of heat flux, etc. Two sets of probe arrays including 274 probe tips were placed at two ports (approximately 180° separated toroidally), and the spatial and temporal resolutions of this measurement system could reach 6 mm and 1 s, respectively. A novel design of the ceramic isolation ring can ensure reliable electrical insulation property between the graphite tip and the copper substrate plate where plasma impurities and the dust are deposited into the gaps for a long experimental time. Meanwhile, the condition monitoring and mode conversion between single and triple probe of the probe system could be conveniently implemented via a remote control station. The preliminary experimental result shows that the divertor Langmuir probe system is capable of measuring the high spatiotemporal parameters involved the plasma density, electron temperature, particle flux as well as heat flux during the ELMy H-mode discharges.

Effect of gender, carrying and planting the pole on approach step parameters in young pole vaulters

In pole vaulting, take-off speed is considered as a major determinant of performance. Pole carriage could affect the speed acquired during the approach and at the take-off. This study investigated different types of runs performed randomly by young male and female expert athletes: maximal sprint, maximal pole carriage run, maximal run-up with simulated pole plant and competition situation. Speed profile was determined with a radar gun and spatiotemporal parameters were recorded for the last 20 m of the approach with the Optojump Next system. For both genders, mechanical variables were compared using two-way ANOVAs with repeated measurements. Pole carriage represents the main cause of speed decrease for both men (−5.8%) and women (−6.2%). A step rate decrease during pole carriage was pointed out with an increase of contact time for both men and women. Significant speed decrease was observed for women at the take-off compared to pole plant simulation (−4.3%), while not for men. Those results provide a new insight for pole vault training allowing to update training process with specific exercises leading to reduce speed loss at take-off.

Effects of Robot-Assisted Therapy on Gait Parameters in Pediatric Patients With Spastic Cerebral Palsy

Background: Gait dysfunction is a crucial factor that restricts independence and quality of life in children with cerebral palsy (CP). Gait training based on robotic-assisted therapy (RAT) is widely used, but information about effectiveness and ideal patient profile is not sufficient. Aim of this study was to assess the effect of RAT on gait parameters in spastic children with CP, and to determine whether changes in gait parameters are different among patients on different ambulatory levels.Method: A total of 26 children with bilateral spastic CP were divided into two groups based on their functional ability: non-assisted ambulator (NAS) or assisted ambulator (AS); and underwent a RAT program (30 training sessions of RAT during 10 weeks). Gait analysis was performed: before the therapy (t1), right after (t2), and 6 weeks later (t3).Results: No significant changes in spatiotemporal parameters or gait deviation index at t2 or t3. Double support symmetry significantly improved (t1 vs. t3, p = 0.03) for the whole group (NAS + AS). Walking speed symmetry significantly improved (t2 vs. t3, p = 0.02) for group AS.Conclusion: RAT based on our protocol did not change spatiotemporal parameters and kinematics of walking except limited improvement in some aspects of gait symmetry. We did not find differences in changes in selected objective gait parameters among children with CP in different ambulatory levels.

A mechanistically interpretable model of the retinal neural code for natural scenes with multiscale adaptive dynamics

The visual system processes stimuli over a wide range of spatiotemporal scales, with individual neurons receiving input from tens of thousands of neurons whose dynamics range from milliseconds to tens of seconds. This poses a challenge to create models that both accurately capture visual computations and are mechanistically interpretable. Here we present a model of salamander retinal ganglion cell spiking responses recorded with a multielectrode array that captures natural scene responses and slow adaptive dynamics. The model consists of a three-layer convolutional neural network (CNN) modified to include local recurrent synaptic dynamics taken from a linear-nonlinear-kinetic (LNK) model \cite{ozuysal2012linking}. We presented alternating natural scenes and uniform field white noise stimuli designed to engage slow contrast adaptation. To overcome difficulties fitting slow and fast dynamics together, we first optimized all fast spatiotemporal parameters, then separately optimized recurrent slow synaptic parameters. The resulting full model reproduces a wide range of retinal computations and is mechanistically interpretable, having internal units that correspond to retinal interneurons with biophysically modeled synapses. This model allows us to study the contribution of model units to any retinal computation, and examine how long-term adaptation changes the retinal neural code for natural scenes through selective adaptation of retinal pathways.

Characterization of Anticipatory Postural Adjustments in Lateral Stepping: Impact of Footwear and Lower Limb Preference

Lateral stepping is a motor task that is widely used in everyday life to modify the base of support, change direction, and avoid obstacles. Anticipatory Postural Adjustments (APAs) are often analyzed to describe postural preparation prior to forward stepping, however, little is known about lateral stepping. The aim of the study is to characterize APAs preceding lateral steps and to investigate how these are affected by footwear and lower limb preference. Twenty-two healthy young participants performed a lateral step using both their preferred and non-preferred leg in both barefoot and shod conditions. APA spatiotemporal parameters (size, duration, and speed) along both the anteroposterior and mediolateral axes were obtained through force plate data. APAs preceding lateral stepping showed typical patterns both along the anteroposterior and mediolateral axis. RM-ANOVA highlighted a significant effect of footwear only on medio-lateral APAs amplitude (p = 0.008) and velocity (p = 0.037). No differences were found for the limb preference. APAs in lateral stepping presented consistent features in the sagittal component, regardless of limb/shoe factors. Interestingly, the study observed that footwear induced an increase in the medio-lateral APAs size and velocity, highlighting the importance of including this factor when studying lateral stepping.

Assessment of the Kinematic Adaptations in Parkinson’s Disease Using the Gait Profile Score: Influences of Trunk Posture, a Pilot Study

Introduction: Postural abnormalities are common in patients with Parkinson’s disease (PD) and lead to gait abnormalities. Relationships between changes in the trunk posture of PD patients and gait profile score (GPS) and gait spatiotemporal parameters are poorly investigated. The aim of the current study was to investigate the relationships between trunk posture, GPS, and gait spatiotemporal parameters, in patients with PD. Materials and Methods: Twenty-three people with PD and nineteen age-matched healthy people participated in this study. A 3D gait kinematical analysis was applied to all participants using the Plug-In Gait Full BodyTM tool. Trunk and limb kinematics patterns and gait spatio-temporal parameters of patients with PD and the control group were compared. Additionally, correlations between trunk kinematics patterns, gait spatio-temporal parameters, and GPS of the PD group were tested. Results: Cadence, opposite foot off, step time, single support, double support, foot off, gait speed, trunk kinematics, and GPS showed significant differences between the two groups (p ≤ 0.05). Posture of the trunk during gait was not related to the spatio-temporal parameters and gait profile score in the PD group. The trunk flexor pattern influenced GPS domains, mainly of the ankle and the knee. Discussion and Conclusions: Flexed posture of the trunk in patients with PD seems to influence both ankle and knee movement patterns during the gait. The GPS analysis provided direct and simplified kinematic information for the PD group. These results may have implications for understanding the importance of considering the positioning of the trunk during gait.

Spatiotemporal Parameters And Gait Variability In People With Psoriatic Arthritis (Psa) : A Cross-Sectional Study.

Background: Foot involvement is a major manifestation of psoriatic arthritis (PsA) and could lead to severe levels of foot pain and disability and impaired functional mobility and quality of life. Gait spatiotemporal parameters (STPs) and gait variability, used as a clinical index of gait stability, have been associated with several adverse health outcomes including risk of falling, functional decline, and mortality in a wide range of populations. Previous studies showed some alterations in STPs in people with PsA. However, gait variability and the relationships between STPs, gait variability and self-reported foot pain and disability have never been studied in this populations. Body-worn inertial measurement units (IMUs) are gaining interest in measuring gait parameters in clinical settings.Objectives: To assess STPs and gait variability in people with PsA using IMUs and, to explore their relationship with self-reported foot pain and function and to investigate the feasibility of using IMUs to discriminate patient groups based on gait speed-critical values.Methods: 21 participants with PsA (Age: 53.9 ± 8.9 yrs; median disease duration: 6 yrs) and 21 age and gender-matched healthy participants (Age 54.23 ± 9.3 yrs) were recruited. All the participants performed three 10-meter walk test trials at their comfortable speed. STPs and gait variability were recorded and calculated using six body-worn IMUs and the Mobility Lab software (APDM®). Foot pain and disability were assessed in participants with PsA using the foot function index (FFI).Results: Cadence, gait speed, stride length, and swing phase, were significantly lower, while double support was significantly higher, in the PsA group (p< 0.006). Strong correlations between STPs and the FFI total score were demonstrated (|r|> 0.57, p< 0.006). Gait variability was significantly increased in the PsA group, but it was not correlated with foot pain and function (p< 0.006). Using the IMUs three subgroups of participants with PsA with clinically meaningful differences in self-reported foot pain and disability were discriminated.Conclusion: STPs were significantly altered in participants with PsA which could be associated with self-reported foot pain and disability. Future studies are required to confirm the increased gait variability highlighted in this study and its potential underlying causes. Using IMUs in clinical settings has been useful to objectively assess foot function in people with PsA. Study registration: ClinicalTrials.gov, NCT05075343, Retrospectively registered on 29 September 2021.

The effects of ankle-foot orthoses with plantar flexion stop and plantar flexion resistance using rocker-sole shoes on stroke gait: A randomized-controlled trial

Objectives: This study aims to evaluate the effect of two ankle-foot orthoses (AFOs), AFO with plantar flexion stop (AFO-PlfS), and AFO with plantar flexion resistance (AFO-PlfR), while wearing standard shoes and rocker-sole shoes. Patients and methods: Between November 2017 and July 2018, in this randomized-controlled study, a total of 20 stroke patients (8 males, 12 females; mean age: 48.1 years; range, 33 to 65 years) in chronic phase were randomized to AFO groups (AFO-PlfS group, n=10 and AFO-PlfR group, n=10). Each group received the allocated AFO along with two kinds of shoes (standard shoe and rocker shoe) for a two-week adaptation. Two effects were separately evaluated: The orthotic effect and rocker shoe effect were defined as the evaluation of using an AFO wearing standard shoe compared to only standard shoe, and evaluation of using an AFO wearing rocker shoe compared to an AFO wearing standard shoe, respectively. The gait of each group was measured by three-dimensional motion analysis. Results: A significant orthotic effect was found in both AFO groups in spatiotemporal parameters and maximum ankle dorsiflexion in the single-support phase. Additionally, the AFO-PlfR group showed a significant improvement in the parameters related to the first rocker of gait, but not for AFO-PlfS group concerning the orthotic effect. The rocker shoe effect was found in significant reduction of peak ankle plantar flexor moment and power ankle generation during preswing for both AFO groups. Conclusion: According to the orthotic effect, an AFO-PlfR can create better function in the improvement of parameters related to the first rocker. Although a rocker shoe can facilitate rollover for weight progression in the third rocker of gait, it cannot make a strong push-off function in stroke survivors.