Sway Amplitude Research Articles

Visual Perturbation Suggests Increased Effort to Maintain Balance in Early Stages of Parkinson's to be an Effect of Age Rather Than Disease.

Postural instability marks a prevalent symptom of Parkinson’s disease (PD). It often manifests in increased body sway, which is commonly assessed by tracking the Center of Pressure (CoP). Yet, in terms of postural control, the body’s Center of Mass (CoM), and not CoP is what is regulated in a gravitational field. The aim of this study was to explore the effect of early- to mid-stage PD on these measures of postural control in response to unpredictable visual perturbations. We investigated three cohorts: (i) 18 patients with early to mid-stage PD [Hoehn & Yahr stage (1–3); 1.94 ± 0.70]; (ii) a group of 15 age-matched controls (ECT); and (iii) a group of 12 young healthy adults (YCT). Participants stood on a force plate to track their CoP, while the movement of their entire body was recorded with a video-based motion tracking system to monitor their CoM. A moving room paradigm was applied through a head-mounted virtual reality headset. The stimulus consisted of a virtual tunnel that stretched in the anterior-posterior direction which either remained static or moved back and forth in an unpredictable fashion.We found differences in mean sway amplitude (MSA) and mean velocities of CoP and CoM between the groups under both conditions, with higher MSA of CoP and CoM for PD and higher mean velocities of both variables for PD and ECT when compared with YCT. Visual perturbation increased mean CoP velocity in all groups but did not have effects on mean CoM velocity or MSA. While being significantly lower for the young adults, the net effect of visual perturbation on mean CoP velocity was similar between patients with PD and age-matched controls. There was no effect of the visual perturbation on mean CoM velocity for any of the groups.Our simultaneous assessment of CoP and CoM revealed that postural control is reflected differently in CoM and CoP. As the motion of CoM remained mostly unaffected, all groups successfully counteracted the perturbation and maintained their balance. Higher CoP velocity for PD and ECT revealed increased corrective motion needed to achieve this, which however was similar in both groups. Thus, our results suggest increased effort, expressed in CoP velocity, to be an effect of age rather than disease in earlier stages of PD.

Haptic Information Improvement on Postural Sway is Information-Dependent But Not Influenced by Cognitive Task

Young adults reduce their sway in both light touch (LT) and anchor systems (AS), however, the cognitive involvement in these tasks is unknown. This study investigated postural control in young adults standing upright using either LT or AS, concomitantly with a cognitive task (counting). Nine adults (26 ± 7.4 years) stood in the upright tandem stance with eyes closed, with/without LT, AS (force <2 N), and a cognitive task. The mean sway amplitude of the trunk, right wrist, and shoulder ellipse area, as well as the mean force during LT and AS were obtained. The cognitive task did not influence the magnitude of trunk sway or the mean force in the LT and AS conditions. The trunk sway magnitude was reduced in the AS and even further in LT. Wrist and shoulder variability was larger in the AS than in the LT. Based on these results, we conclude that enhanced sensory cues provided by LT and AS reduce trunk sway with little or no attentional demands.

Wind speed inference from environmental flow–structure interactions. Part 2. Leveraging unsteady kinematics

Abstract This work explores the relationship between wind speed and time-dependent structural motion response as a means of leveraging the rich information visible in flow–structure interactions for anemometry. We build on recent work by Cardona, Bouman and Dabiri (Flow, vol. 1, 2021, E4), which presented an approach using mean structural bending. Here, we present the amplitude of the dynamic structural sway as an alternative signal that can be used when mean bending is small or inconvenient to measure. A force balance relating the instantaneous loading and instantaneous deflection yields a relationship between the incident wind speed and the amplitude of structural sway. This physical model is applied to two field datasets comprising 13 trees of 4 different species exposed to ambient wind conditions. Model generalization to the diverse test structures is achieved through normalization with respect to a reference condition. The model agrees well with experimental measurements of the local wind speed, suggesting that tree sway amplitude can be used as an indirect measurement of mean wind speed, and is applicable to a broad variety of diverse trees.

Vratna kinestezija kao značajan doprinos u zaštiti posturalne stabilnosti kod taekvondo boraca

Taekwondo fighters require sufficient postural stability to maintain tactical superiority over an opponent. Postural balance is controlled by somatosensory, visual and vestibular system. Cervical spine has neurophysiological connection to the visual and vestibular system as well as abundance of receptors within the connective tissues of the spine. Guard-specific posture in taekwondo requires constant head and neck rotations, therefore deficits in cervical spine could alter the balance. The aim of the study was to study connections between cervical spine kinesthesia and balance in taekwondo specific postural tasks. Sixteen healthy male taekwondo fighters (22 ±1,3 years of age) competing at the national level were enrolled in the study. Postural balance during a single leg stance while facing forward or with 90° of neck torsion using a force plate (Bilateral force plate, S2P, Ljubljana, Slovenia) was assessed. Kinesthetic awareness of cervical spine was measured using a Butterfly test with a NeckCare system (Butterfly Method, NeckCare ehf., Reykjavik, Iceland). Statistically significant correlations were observed for Undershoot standard deviation of the Butterfly test and Neck torsion balance test while standing on the non-dominant leg. These correlations were most prominent for the average amplitude of centre of pressure movement in the medial-lateral direction (r &gt; 0.85) and anterior posterior direction (r &gt; 0,80) Results of this study indicate that taekwondo fighters develop side specific adaptations in the balance control. Increased variability of cervical spine kinesthetic awareness is correlated to an increased average amplitude of medial-lateral body sway while standing on the kick preferred leg. This can lead to higher body oscillations during the fight, decreased stability, prolonged reaction time and quickness. Specific cervical spine training is recommended to improve fighting performance.

Evaluation of Postural Sway in Post-stroke Patients by Dynamic Time Warping Clustering.

Post-stroke complications are the second most frequent cause of death and the third leading cause of disability worldwide. The motor function of post-stroke patients is often assessed by measuring the postural sway in the patients during quiet standing, based on sway measures, such as sway area and velocity, which are obtained from temporal variations of the center of pressure. However, such approaches to establish a relationship between the sway measures and patients' demographic factors have hardly been successful (e.g., days after onset). This study instead evaluates the postural sway features of post-stroke patients using the clustering method of machine learning. First, we collected the stroke patients' multi-variable motion-capture standing-posture data and processed them into t s long data slots. Then, we clustered the t-s data slots into K cluster groups using the dynamic-time-warping partition-around-medoid (DTW-PAM) method. The DTW measures the similarity between two temporal sequences that may vary in speed, whereas PAM identifies the centroids for the DTW clustering method. Finally, we used a post-hoc test and found that the sway amplitudes of markers in the shoulder, hip, knee, and center-of-mass are more important than their sway frequencies. We separately plotted the marker amplitudes and frequencies in the medial-lateral direction during a 5-s data slot and found that the post-stroke patients' postural sway frequency lay within the bandwidth of 0.5–1.5 Hz. Additionally, with an increase in the onset days, the cluster index of cerebral hemorrhage patients gradually transits in a four-cluster solution. However, the cerebral infarction patients did not exhibit such pronounced transitions over time. Moreover, we found that the postural-sway amplitude increased in clusters 1, 3, and 4. However, the amplitude of cluster 2 did not follow this pattern, owing to age effects related to the postural sway changes with age. A rehabilitation doctor can utilize these findings as guidelines to direct the post-stroke patient training.

Dynamic Visual Stimulations Produced in a Controlled Virtual Reality Environment Reveals Long-Lasting Postural Deficits in Children With Mild Traumatic Brain Injury.

Motor control deficits outlasting self-reported symptoms are often reported following mild traumatic brain injury (mTBI). The exact duration and nature of these deficits remains unknown. The current study aimed to compare postural responses to static or dynamic virtual visual inputs and during standard clinical tests of balance in 38 children between 9 and 18 years-of-age, at 2 weeks, 3 and 12 months post-concussion. Body sway amplitude (BSA) and postural instability (vRMS) were measured in a 3D virtual reality (VR) tunnel (i.e., optic flow) moving in the antero-posterior direction in different conditions. Measures derived from standard clinical balance evaluations (BOT-2, Timed tasks) and post-concussion symptoms (PCSS-R) were also assessed. Results were compared to those of 38 healthy non-injured children following a similar testing schedule and matched according to age, gender, and premorbid level of physical activity. Results highlighted greater postural response with BSA and vRMS measures at 3 months post-mTBI, but not at 12 months when compared to controls, whereas no differences were observed in post-concussion symptoms between mTBI and controls at 3 and 12 months. These deficits were specifically identified using measures of postural response in reaction to 3D dynamic visual inputs in the VR paradigm, while items from the BOT-2 and the 3 timed tasks did not reveal deficits at any of the test sessions. PCSS-R scores correlated between sessions and with the most challenging condition of the BOT-2 and as well as with the timed tasks, but not with BSA and vRMS. Scores obtained in the most challenging conditions of clinical balance tests also correlated weakly with BSA and vRMS measures in the dynamic conditions. These preliminary findings suggest that using 3D dynamic visual inputs such as optic flow in a controlled VR environment could help detect subtle postural impairments and inspire the development of clinical tools to guide rehabilitation and return to play recommendations.

Trunk and head displacements stabilized to perform both horizontal and vertical saccadic eye movements.

Vision is crucial for humans to interact with their surrounding environment, and postural sway is reduced to allow short eye movements. However, the extent of subtle changes in postural control for horizontal and vertical eye movements remains unclear. The goal of this study was to investigate the effects of vertical and horizontal eye movements on head and trunk control in young adults. Fifteen healthy adults (23.4 ± 4.7years) stood upright in three conditions for 60s: fixation, horizontal, and vertical guided eye movements. In fixation, participants had to fixate on a stationary target. In both the horizontal and vertical eye movements, the target was presented with a frequency of 0.5Hz and a visual angle of 11°. Eye displacement was monitored using a SMI eye tracker (ETG2.0) and trunk and head sway were monitored using infrared markers (Optotrak 3020, NDI). The mean sway amplitude was lower in both directions for eye movements and lowest in the vertical direction compared to the fixation condition. The sway area was also lower in vertical eye movement than in the fixation condition. We also found that the sway reduction was greater at head than at trunk level. The median frequency sway in the anterior-posterior direction was higher in both eye movements than in fixation. Based upon these results, we suggest that to perform short eye movements, postural sway is more strongly controlled at the head level than at the trunk and in vertical eye movements than in horizontal movements.

Force Control on Fingertip Using EMS to Maintain Light Touch.

Light touch on a rigid surface with minimal force below a specific threshold reduces postural sway by providing additional sensory cues from the fingertips. The feasibility of maintaining light touch depends on subject characteristics and task difficulty. Therefore, we introduce a method of maintaining light touch by using electrical muscle stimulation (EMS). We applied it in a single-leg standing task involving healthy adult subjects. The subjects stood upright in a single-leg stance on a firm surface and on foam rubber (FR), respectively, under three conditions: no touch (NT, NT-FR), light touch without EMS (LT, LT-FR), and light touch in which EMS was applied based on the contact force (LT-EMS, LT-EMS-FR). The results showed that the force control by EMS helped maintain light touch and reduce postural sway compared with the no-touch condition. The amplitude of postural sway under the touch condition with EMS was equivalent to that under the touch condition without EMS.

Activation of the Prefrontal Cortex and Improvement of Cognitive Performance with Standing on One Leg

The prefrontal cortex (PFC) is involved in attention, motor planning, and executive functions. In addition, it is known that postural control and cognitive performance are affected during dual-task paradigms, suggesting that postural control and cognition use common areas of the brain. Although postural control and cognition have been used as interfering dual tasks, the neuronal mechanisms underlying interference are not fully understood. We simultaneously performed postural and cognitive tasks in healthy young adults and evaluated activity in the PFC using near-infrared spectrometry. The displacement of the center of pressure (COP) is reduced by cognitive tasks. Difficult postural tasks increased the relative proportion and amplitude of postural sway in the high-frequency bandwidth, related to the adjustment of postural sway. Although the cognitive tasks did not affect the relative proportion of each frequency bandwidth, the amplitudes were selectively reduced. The postural task-dependent change in PFC activity was correlated with the relative proportion and amplitude of postural sway in the high-frequency bandwidth of the COP movement. Cognitive task-dependent changes in PFC activity were not correlated with postural sway. Cognitive performance was better in unipedal standing than bipedal standing. These findings suggest that postural tasks affect cognitive performance via the activation of the PFC, but cognitive tasks affect postural control through a different mechanism.

Performance of postural balance in children and adolescents living with and without HIV

Research questionThe present study aimed to compare the postural control of children and adolescents with and without Human Immunodeficiency Virus (HIV). MethodsA total of 32 children and adolescents (18 with HIV and 14 without) of both sexes, aged 6–18 years, were included in the present study. Participants in the HIV + group were infected through vertical transmission and received antiretroviral therapy. Participants maintained an erect, bipedal posture in the following conditions: with vision, without vision, and on a foam base. ResultsConcerning the evaluation of time variables, higher values ​​were observed in the HIV + group for mean anterior-posterior (AP) velocity, mean medial-lateral (ML) velocity, AP perimeter (p = 0.001), and ML perimeter (p = 0.001). Concerning the evaluation of conditions, a difference was observed in the mean AP mean sway amplitude (MSA) (p = 0.039), as the AP MSA was lower with vision than without vision or with foam. Concerning the evaluation of spectral domain variables, higher values ​​were observed in the HIV+ group for the predominant ML frequency (p = 0.04) and mean AP (p = 0.001) and ML frequencies (p = 0.001). Regarding the evaluation of conditions, a difference was found only in the predominant AP frequency (p = 0.001). Higher values ​​were found in the closed eye condition than in with foam (Δ = +103 %). ConclusionThe results of the present study indicated that children and adolescents living with HIV have poorer postural control performance than those without HIV.

Postural Balance Ability and the Effect of Visual Restriction on Older Dancers and Non-Dancers.

Dance has been suggested to be an advantageous exercise modality for improving postural balance performance and reducing the risk of falls in the older population. The main purpose of this study was to investigate whether visual restriction impacts older dancers and non-dancers differently during a quiet stance balance performance test. We hypothesized higher balance performance and greater balance deterioration due to visual restriction in dancers compared with non-dancers, indicating the superior contribution of the visual channel in the expected higher balance performances of dancers. Sixty-nine (38 men, 31 women, 74 ± 6 years) healthy older adults participated and were grouped into a Greek traditional dance group (n = 31, two to three times/week for 1.5 h/session, minimum of 3 years) and a non-dancer control group (n = 38, no systematic exercise history). The participants completed an assessment of one-legged quiet stance trials using both left and right legs and with eyes open while standing barefoot on a force plate (Wii, A/D converter, 1,000 Hz; Biovision) and two-legged trials with both eyes open and closed. The possible differences in the anthropometric and one-legged balance parameters were examined by a univariate ANOVA with group and sex as fixed factors. This ANOVA was performed using the same fixed factors and vision as the repeated measures factor for the two-legged balance parameters. In the one-legged task, the dance group showed significantly lower values in anteroposterior and mediolateral sway amplitudes (p = 0.001 and p = 0.035) and path length measured in both directions (p = 0.001) compared with the non-dancers. In the two-legged stance, we found a significant vision effect on path length (p < 0.001) and anteroposterior amplitude (p < 0.001), whereas mediolateral amplitude did not differ significantly (p = 0.439) between closed and open eyes. The dance group had a significantly lower CoP path length (p = 0.006) and anteroposterior (p = 0.001) and mediolateral sway amplitudes (p = 0.003) both in the eyes-open and eyes-closed trials compared with the control group. The superior balance performance in the two postural tasks found in the dancers is possibly the result of the coordinated, aesthetically oriented intersegmental movements, including alternations between one- and two-legged stance phases, that comes with dance. Visual restriction resulted in a similar deterioration of balance performance in both groups, thus suggesting that the contribution of the visual channel alone cannot explain the superior balance performance of dancers.

Inertial Sensor Reliability and Validity for Static and Dynamic Balance in Healthy Adults: A Systematic Review.

Compared to laboratory equipment inertial sensors are inexpensive and portable, permitting the measurement of postural sway and balance to be conducted in any setting. This systematic review investigated the inter-sensor and test-retest reliability, and concurrent and discriminant validity to measure static and dynamic balance in healthy adults. Medline, PubMed, Embase, Scopus, CINAHL, and Web of Science were searched to January 2021. Nineteen studies met the inclusion criteria. Meta-analysis was possible for reliability studies only and it was found that inertial sensors are reliable to measure static standing eyes open. A synthesis of the included studies shows moderate to good reliability for dynamic balance. Concurrent validity is moderate for both static and dynamic balance. Sensors discriminate old from young adults by amplitude of mediolateral sway, gait velocity, step length, and turn speed. Fallers are discriminated from non-fallers by sensor measures during walking, stepping, and sit to stand. The accuracy of discrimination is unable to be determined conclusively. Using inertial sensors to measure postural sway in healthy adults provides real-time data collected in the natural environment and enables discrimination between fallers and non-fallers. The ability of inertial sensors to identify differences in postural sway components related to altered performance in clinical tests can inform targeted interventions for the prevention of falls and near falls.

Movement kinematics and cortical activation in children with and without autism spectrum disorder during sway synchrony tasks: an fNIRS study

Children with Autism Spectrum Disorder (ASD) have difficulties with socially embedded movements such as imitation and interpersonal synchrony (IPS); however, related movement characteristics and underlying neural mechanisms are not well understood. This study compared the movement characteristics and cortical activation patterns of children with and without ASD during a whole-body, sway synchrony task when different levels of social information were provided. Thirty children with and without ASD (mean age: 12.6 years, SE: 0.6 years) participated. Movement kinematics and fNIRS-based cortical activation were recorded when the child observed an adult tester sway side to side, when they swayed solo, or when they swayed face to face with the tester with or without fingertips touching (i.e., IPS). Children with ASD showed reduced synchrony and smaller sway amplitude compared to typically developing children without ASD. They showed reduced cortical activation over the inferior frontal gyrus and superior temporal sulcus during IPS and did not show significant increase in cortical activation when more social information was provided. The cortical activation findings were significantly associated with IPS behaviors and social communication performance. The ASD-related neurobiomarkers identified in our study could be used as objective measures to evaluate intervention effects in children with ASD.

Type of exercise may influence postural adaptations in chemotherapy-induced peripheral neuropathy.

ObjectiveTraditional posturography measurements characterize postural instability in patients with chemotherapy‐induced peripheral neuropathy (CIPN), while underlying postural control mechanisms remain unclear. Taking a model‐based approach can yield insights into these mechanisms. This study’s aim was to characterize the modifications in postural control of CIPN patients associated with exercise in relation to the postural behavior of healthy control participants (hCON) via an exploratory approach.MethodsThirty‐one CIPN patients were randomly assigned to two interventions (balance plus moderate endurance training vs. moderate endurance training only) and exercised twice per week over 12 weeks. Baseline data were compared to 36 matched hCONs. We recorded spontaneous sway and postural reactions to platform tilts using Optotrak and a Kistler force platform pre‐ and post‐intervention. Data interpretation relied on a model‐based parameter identification procedure.ResultsSpontaneous sway amplitudes were larger and postural reactions smaller, with a relative phase advance, in our pre‐intervention patients than the hCONs. Post‐intervention, spontaneous sway, and postural reactions were reduced and the sensory‐motor ratio larger in both groups, while the postural reaction timing differed between groups.InterpretationThe abnormally small postural reactions in CIPN patients before the intervention can be interpreted as the consequence of abnormally strong velocity control—a strategy modification that may serve as a prediction mechanism to compensate for the lack of timely and accurate proprioceptive signals. While both groups reduced postural sway and showed an adapted sensory‐motor ratio post‐intervention, the interventions seemed to trigger different velocity control strategies. This study emphasizes the need for taking a more differentiated perspective on intervention effects.Trial registrationGerman Clinical Trials Register (DRKS) number: DRKS00005419, prospectively registered on November 19, 2013.

Niacin Enhancement for Parkinson’s Disease: An Effectiveness Trial

We previously reported that individuals with Parkinson’s disease (PD) present with lower vitamin B3 levels compared to controls. It may be related to carbidopa interaction, defective tryptophan metabolism, and stresses of night sleep disorder. Vitamin B3 is the energy source for all cells by producing NAD+ and NADP+ in redox reactions of oxidative phosphorylation. Thus, some symptoms of PD such as fatigue, sleep dysfunction, and mood changes may be related to the deficiency of vitamin B3. Here, we conducted an effectiveness trial to determine the effect of 12 months of low-dose niacin (a vitamin B3 derivative) enhancement in PD individuals. An average of 9 ± 6-point improvement in the Unified Parkinson’s Disease Rating Scale (UPDRS) III (motor) score was observed after 12 months of daily niacin compared to the expected decline in score (effect size = 0.78, 95% CI = 7–11). Additionally, secondary outcome measures improved. Notably, handwriting size increased, fatigue perception decreased, mood improved, frontal beta rhythm during quiet stance increased, and stance postural sway amplitude and range of acceleration decreased. Set shifting, however, as measured by the Trail Making-B test, worsened from 66 to 96 s. Other measures did not change after 12 months, but it is not clear whether this represents a positive benefit of the vitamin. For example, while the quality of night sleep remained the same, there was a trend towards a decrease in the frequency of awakening episodes. These results suggest that niacin enhancement has the potential to maintain or improve quality of life in PD and slow disease progression.

Relations between postural sway and cognitive workload during various gaze tasks in healthy young and old people.

The purpose of this study was to determine whether postural control would differ under various gaze tasks while standing in a wide or narrow stance between healthy young and old people, and also investigate whether postural sway and cognitive workload are affected by dual-task balance. Ten young and 10 healthy old people participated in this study. Each participant stood upright under four gaze conditions (fixation, saccade, pursuit, vestibular-ocular reflex) and two stance conditions (wide and narrow stance) in a total of 16 trials. Postural sway was measured by the mean sway amplitude of the center of pressure in the medial-lateral and anteriorposterior directions. Cognitive workload was measured through pupil response as an index of cognitive activity (ICA) by using Eye tracking system and Eyeworks. The results showed that postural sway significantly reduced when performing saccadic eye movement in both groups but greater postural sway was evoked in vestibular-ocular reflex condition. In addition, although old people had a significant increase in ICA compared to the young, there were no significant differences among all the gaze conditions in old people. These results confirmed that saccadic eye movements are the most beneficial for reducing postural sway regardless of aging and also provide some insight that pupil response represents an indicator of cognitive workload during dual-task balance context. These findings suggest that eye movement exercises may be considered as an effective intervention to improve postural control so a fall prevention program applying eye movement should be extended to individuals who are at risk of falling.

Motion characteristics of a barge-type floating vertical-axis wind turbine with moonpools

The studies on floating offshore wind turbines have been increasing over recent decades due to the growing investments of industries in marine renewable energy. Compared with horizontal-axis wind turbines, research on vertical-axis wind turbines is relatively few, though the latter may have advantages over the former in some aspects, for example, potentially lower cost of energy. In this paper, the characteristics of the motion responses of a barge-type floating system with four moonpools and a vertical-axis wind turbine are experimentally and numerically investigated. The focus is on the gyroscopic effects of turbine rotations on the motion responses of the floating system under different wave conditions. Physical model tests are conducted in a wave tank, where a 2-MW-class turbine is modelled in the 1:100 scale. It is found that the first-order sway and roll motion amplitudes near the resonant frequencies are reduced by the turbine rotations, whereas the first-order heave motion of the floating system is hardly influenced. The second-order motion responses and mooring tether tensions may be significantly amplified with the increasing rotating speed of turbine. The maximum ratio of the second-order response amplitude of roll motion to the first-order roll amplitude is up to 17% in the experiments of this study. A radiation and diffraction code based on linear potential flow theory is used to predict the motion responses and mooring forces. The comparisons with experimental data suggest that the viscous damping of water resonance in moonpools and the gyroscopic effects of turbine rotations should be taken into account in predictions.

Compromised cognition, but not stepping-down performance, when dual-tasking in stroke survivors

Descending stairs is an indicator of independence among stroke survivors, but is demanding in terms of both neuromuscular control and cognitive functioning. Previous studies found a compromised performance when stepping down with a concurrent cognitive task among healthy older adults, but whether stroke survivors react similarly is not known. This cross-sectional study thus investigated how stroke survivors responded to a dual-task that involved stepping down and compared their performance with that of control subjects. Thirty-four healthy individuals and 26 stroke survivors reacted to an auditory Stroop test while stepping off a 19-cm high platform. The auditory Stroop test was evaluated with a composite score (dividing accuracy by averaged reaction time). Stepping down performances were quantified with subjects’ sway amplitudes in anteroposterior and mediolateral directions after landing and sway velocities of their center of pressure. Stroke survivors demonstrated significantly lower composite scores when dual-tasking (76.4 ± 31.2) than when single-tasking (90.0 ± 25.6), while no significant change in stepping down performance was observed. Stroke survivors also swayed significantly more and with a higher velocity than controls when dual-tasking. The results suggested that stroke survivors adopted a posture-first strategy to deal with this dual-tasking challenge. This study raised the awareness on dual-tasking ability among stroke survivors.

A meta-analysis and systematic review of changes in joint position sense and static standing balance in patients with whiplash-associated disorder.

ObjectiveTo synthesise and analyse the current evidence regarding changes in joint position sense (JPS) and standing balance in people with whiplash-associated disorder (WAD) taking the presence or absence of dizziness into account.Data sourcesPubMed, CINAHL Plus, Web of Science, Embase, MEDLINE and APA PsycINFO were searched by two independent reviewers from inception until August 2020 and reference lists of all included studies were also reviewed.Study selectionOnly cross-sectional studies that measured JPS and/or standing balance between people with WAD vs. healthy controls (HC) or people with WAD complaining of dizziness (WADD) vs. those not complaining of dizziness (WADND) were selected.Data extractionRelevant data were extracted using specific checklists and quality assessment was performed using Downs and Black Scale (modified version).Data synthesisTwenty-six studies were included. For JPS, data were synthesized for absolute error in the primary plane of movement for separate movement directions. For standing balance, data were synthesized for traditional time- and frequency domain sway parameters considering the conditions of eyes open (EO) and eyes closed (EC) separately. For meta-analysis, reduced JPS was observed in people with WAD compared to HC when the head was repositioned to a neutral head position (NHP) from rotation (standardised mean difference [SMD] = 0.43 [95%: 0.24–0.62]) and extension (0.33 [95%CI: 0.08–0.58]) or when the head was moved toward 50° rotation from a NHP (0.50 [0.05–0.96]). Similarly, people with WADD had reduced JPS compared to people with WADND when the head was repositioned to a NHP from rotation (0.52 [0.22–0.82]). Larger sway velocity and amplitude was found in people with WAD compared to HC for both EO (0.62 [0.37–0.88] and 0.78 [0.56–0.99], respectively) and EC (0.69 [0.46–0.91] and 0.80 [0.58–1.02]) conditions.ConclusionThe observed changes of JPS and standing balance confirms deficits in sensorimotor control in people with WAD and especially in those with dizziness.

Fundamental diagrams of luggage-laden pedestrians ascending and descending stairs

In transportation terminals, a lot of passengers usually travel with luggage, which affects not only their mobility but also the ones who have no luggage, especially on stairs. As a result, congestion could be severer during rush hours. However, the impact of luggage on the movement characteristics of pedestrians ascending and descending stairs have not been systematically studied yet. Therefore, in this study, a series of single-file luggage-laden movement experiments under controlled laboratory conditions were performed. Trajectories have been extracted to analyze the movement features under different luggage-laden ratio scenarios. From the space–time diagram, it can be found the average stopping time gradually increases as the increase of the luggage-laden ratios. In the relationship between spatial headway and speed, two regimes are found, i.e., free regime and strongly constrained regime. The minimum descending headway is basically the same as the tread depth, while the minimum ascending headway is greater than the tread depth. The pedestrian adaptation time in the scenario of a high luggage-laden ratio is longer than that of none. Finally, in addition to longitudinal movement, with the increase of speed, pedestrian lateral sway amplitude decline rate in the descending process is faster than that in the ascending process. The impact of carrying luggage ascent and descent the stairs on pedestrian movement characteristics provided in this study is helpful not only for the calibration and verification of the pedestrian models but also for the design of pedestrian facilities in transportation terminals.