Postural Control Performance Research Articles

Effective utilization of attentional resources in postural control in athletes of skill-oriented sports: an event-related potential study.

Postural control plays a key role in skill-oriented sports. Athletes of skill-oriented sports (hereinafter referred to as "skilled athletes") usually showed better control ability compared with non-athletes. However, research focused on the single postural task, rarely considering the actual situation in skill-oriented sports in which other processes, such as cognitive control, frequently accompany postural control. This study aims to explore how skilled athletes control their posture under the dual-task situation and use limited attentional resources. A total of 26 skilled athletes and 26 non-athletes were required to perform the postural control and N-back tasks simultaneously. Center of pressure (COP) trajectory, reaction times (RTs), and discriminability (d') of N-back tasks were recorded and evaluated, along with event-related potentials, including N1 (Oz, PO7, and PO8), P2 (Fz, FCz, Cz, and Pz) components, and the spectral power of alpha band. Skilled athletes demonstrated more postural control stability and a higher d' than non-athletes in all dual tasks. Besides, they showed enhanced N1, P2 amplitudes and reduced alpha band power during dual-tasking. Notably, in skilled athletes, a significant negative correlation between N1 amplitude and d' was observed, while significant positive correlations between alpha band power and postural control performance were also identified. This study investigates the potential advantages of skilled athletes in postural control from the view of neuroscience. Compared to non-athletes, skilled athletes could decrease the consumption of attentional resources in postural control and recruit more attentional resources in stimulus discrimination and evaluation in cognitive tasks. Since the allocation of attentional resources plays a crucial part in postural control in skilled athletes, optimizing the postural control training program and the selection of skilled athletes from a dual-task perspective is important.

Assistive Technology Involving Postural Control and Gait Performance for Adults with Stroke: A Systematic Review and Meta-Analysis.

This study aimed to comprehensively summarize assistive technology devices for postural control and gait performance in stroke patients. In the study, we searched for randomized controlled trials (RCTs) published until 31 December 2022 in four electrical databases. The most frequently applied assistive technology devices involving postural stability and gait function for stroke patients were robot-assistive technology devices. Out of 1065 initially retrieved citations that met the inclusion criteria, 30 RCTs (12 studies for subacute patients and 18 studies for chronic patients) were included in this review based on eligibility criteria. The meta-analysis included ten RCTs (five studies for subacute patients and five for chronic patients) based on the inclusion criteria of the data analysis. After analyzing, the variables, only two parameters, the Berg balance scale (BBS) and the functional ambulation category (FAC), which had relevant data from at least three studies measuring postural control and gait function, were selected for the meta-analysis. The meta-analysis revealed significant differences in the experimental group compared to the control group for BBS in both subacute and chronic stroke patients and for the FAC in chronic stroke patients. Robot-assistive training was found to be superior to regular therapy in improving postural stability for subacute and chronic stroke patients but not gait function. This review suggests that robot-assistive technology devices should be considered in rehabilitative approaches for postural stability and gait function for subacute and chronic stroke patients.

Effects of expertise in skill-oriented sports on postural control: An event-related potential study using dual-task paradigm

Postural control is a fundamental aspect of motor skills and is crucial for achieving optimal performance in sports. However, previous studies mainly explored the postural control ability of athletes of skill-oriented sports (skilled athletes) under single postural control conditions, disregarding the processing characteristics of postural control in real sports scenarios. This research used the event-related potential (ERP) to investigate the postural control ability of skilled athletes during the action inhibition process by a dual-task paradigm. The study included 26 skilled athletes and 25 nonathletes who simultaneously completed a postural control task and a Go/Nogo task. The results showed that skilled athletes exhibited superior postural control performance in all three standing positions and higher N1 and P3 component amplitudes than nonathletes. The study illustrated that skilled athletes exhibit higher flexibility in allocating attentional resources to ensure optimal postural control and action inhibition performance. These findings suggest that skilled athletes possess a higher level of control automation in complex standing positions and more efficient and economical brain processing characteristics, which may contribute to their exceptional performance in sports.

Effect of a visual dual task on postural stability-A comparative study using linear and nonlinear methods.

The dual-task experimental paradigm is used to study the attentional demands of postural control. Postural control is impaired in poststroke patients, and dual-task balance studies address the visual needs of postural control in stroke patients. A nonlinear approach can help us understand the overall behavior of the dynamic system. A total of 20 chronic stroke patients and 20 healthy subjects with similar age, height, and weight participated in this study. The stability and complexity of postural control were assessed using linear and nonlinear methods. All data and parameters (center of pressure [COP] velocity, anteroposterior and mediolateral directions displacement, length of COP path, and phase plane) were analyzed using the Kolmogorov-Smirnov test. When postural control was examined based on linear analysis, the results showed that the main effect of the group was not significant, but the main impact of position was significant for all parameters of the COP variation (p < 0.05). Examination of postural control based on nonlinear analysis also showed that the main effect of the group was not significant, and the main effect of status was significant only for the parameters of approximate entropy in both directions and short-term Lyapunov view in the anterior-posterior direction (p < 0.05). According to the results of this study, the assessment of postural control and gait performance in poststroke patients, as well as the dual tasks they have to perform in daily life, is crucial for their independence in activities of daily living.

Static and dynamic postural control assessment in schoolchildren: Reliability and reference values of the Modified Flamingo Test and Bar Test

IntroductionSingle-leg stance tests have been widely used to evaluate static balance, like the Modified Flamingo Test. The evaluation of dynamic balance on small support surfaces is the objective of some tests like the Bar Test. Research questionHow is the performance of postural control during the performance of these tests in schoolchildren between 6 and 11 years of age in both sexes? What are the reference values of these tests in this population? MethodA cross-sectional study in which a total of 282 children. The evaluation included both tests. ResultsThe relative reliability was excellent (Intraclass Correlation Coefficient = 0.84–0.98), and the absolute reliability ranged between 4.5% and 7.1% for coefficient variation and between 0.5 and 1.5 for the standard error of measurement. The average results were 3.8 ± 2.7 floor touches for the Modified Flamingo Test and 5 ± 3.5 m for the Bar Test. The results of both tests improve progressively with the increase of age. DiscussionIt can be asserted that children of different ages, as well as boys and girls of the same age, perform differently in these tests. Particularly, according to the analysis based on age subgroups, there were greater improvements in the performance of both tests between 8 and 11 years of age. ConclusionsThe girls obtained in both tests better results, although between 6 and 7 years of age the differences between sexes are not significant.

Beta cortical oscillatory activities and their relationship to postural control in a standing balance demanding test: influence of aging.

Age-related changes in the cortical control of standing balance may provide a modifiable mechanism underlying falls in older adults. Thus, this study examined the cortical response to sensory and mechanical perturbations in older adults while standing and examined the relationship between cortical activation and postural control. A cohort of community dwelling young (18-30 years, N = 10) and older adults (65-85 years, N = 11) performed the sensory organization test (SOT), motor control test (MCT), and adaptation test (ADT) while high-density electroencephalography (EEG) and center of pressure (COP) data were recorded in this cross-sectional study. Linear mixed models examined cohort differences for cortical activities, using relative beta power, and postural control performance, while Spearman correlations were used to investigate the relationship between relative beta power and COP indices in each test. Under sensory manipulation, older adults demonstrated significantly higher relative beta power at all postural control-related cortical areas (p < 0.01), while under rapid mechanical perturbations, older adults demonstrated significantly higher relative beta power at central areas (p < 0.05). As task difficulty increased, young adults had increased relative beta band power while older adults demonstrated decreased relative beta power (p < 0.01). During sensory manipulation with mild mechanical perturbations, specifically in eyes open conditions, higher relative beta power at the parietal area in young adults was associated with worse postural control performance (p < 0.001). Under rapid mechanical perturbations, specifically in novel conditions, higher relative beta power at the central area in older adults was associated with longer movement latency (p < 0.05). However, poor reliability measures of cortical activity assessments were found during MCT and ADT, which limits the ability to interpret the reported results. Cortical areas are increasingly recruited to maintain upright postural control, even though cortical resources may be limited, in older adults. Considering the limitation regarding mechanical perturbation reliability, future studies should include a larger number of repeated mechanical perturbation trials.

Joint torque parameters of lower limbs and the relationship with postural balance in young adults: a cross-sectional study

BACKGROUND: Different factors can influence the performance of postural control (PC), one of them being muscle function, which emerges as the neuromuscular capacity to generate tension adaptable to postural disturbances in the lower limbs. AIM: To investigate the influence of joint torque parameters of the lower limbs (hip, knee, and ankle) on the variables of postural balance, analyzed by static posturography in young adults. METHOD: This study included 25 young adults (23.08 ± 4.44 years) who were submitted to motor tasks alternating: the base of support; the surface and vision conditions on a force plate. Joint torque was measured using an isokinetic dynamometer. RESULTS: The hip-abduction, -adduction, and -extension torques were negatively associated with the variables of center of pressure displacement in several conditions, both the most challenging and the least challenging ones. The ankle torque (dorsiflexion and plantar flexion) was negatively associated with postural control only in the semi-tandem condition with a rigid surface and eyes open. On the other hand, the knee torque was positively associated with the center of pressure displacement. Power measurements were more associated with postural control than peak torque. CONCLUSION: In young adults, there seems to be a greater use of the hip strategy, with greater influence of hip torque in relation to ankle torque for postural balance control. Therefore, the strengthening of hip muscles could have an impact on postural control in young adults.

Effects of foot preference on postural control in soccer players

A soccer player often uses the dominant leg during activities and the non-dominant leg is used to support body weight. This may have different effects on the postural control between the dominant and non-dominant legs in soccer players. Detection of a possible asymmetry in postural control is important because a bilateral difference may be a contributing factor to injury. This study aimed to compare the postural control performances of right- and left-footed amateur soccer players; secondly, it aimed to address the postural control differences between the dominant and non-dominant legs of soccer players. Twenty-four healthy male soccer players were divided into two different groups (right foot dominant = 12, left foot dominant = 12). Dynamic postural control scores of soccer players in dominant and non-dominant single-stances were measured under two sensory conditions (eyes open and eyes closed) using the Biodex Balance System. In the comparison of two independent groups according to the normality distribution, the t-test and Mann-Whitney U test were used for independent samples. The t-test for dependent samples and the Wilcoxon test were used to compare dependent groups. The results of the study; whether the players are right-footed or left-footed in both eye-open and eye-closed conditions does not affect their postural control performance; showed that the postural control performance of the dominant leg was higher than the non-dominant leg in the eye-open condition of all soccer players regardless of right and left legs. Therefore, it was determined that leg dominance exhibited a symmetrical performance in terms of postural control.

The use of serial casting in the treatment of children with cerebral palsy: a study protocol

Introduction: Cerebral Palsy (CP) is characterized by a disorder of posture and movement, commonly leading to disabling orthopedic alterations, including muscle shortening, especially in the lower limbs. Stretching methods, performed gradually, are necessary to delay the impairment in function from muscle shortening. The use of serial casting aims to promote proper alignment, and an ideal and stable support base, in addition to better bone and joint health, leading to better posture, mobility, muscle function, and, subsequently, increased fitness and health. Objective: evaluate range of motion, postural control, and motor performance in children with CP, using serial casting, as well as to measure its effect on fitness through the autonomic nervous system (ANS). Methods: Sixty children and adolescents with CP, of both sexes, 3 to 12 years of age, will be divided into three groups: Groups A, B, and C, with 20 individuals each. Group A will use serial casting, Group B will use the orthosis continuously (with removal only allowed for bathing), and Group C will use the orthosis in their daily routine. Range of motion of the ankle of first and second resistance levels (R1 and R2), gross motor function measure (GMFM), and balance (measured by BERG scale) will be used in the initial and final assessments, and after 6 months and one year of follow-up. Timed-up-and-go (TUG), load distribution (baropodometry), motor performance measured through a real basketball game and the virtual MoveHero game, analysis of body angulation with “mydartfish”, and cardiac autonomic modulation through heart rate variability will be assessed in three different situations: barefoot, with orthosis, and with casting. Conclusion: Serial casting demonstrates the potential to produce positive results in the treatment of individuals with CP regarding better alignment, with consequent motor and autonomic improvement.

Lifespan changes in postural control

Lifespan development of postural control shows as an inverted U-shaped function with optimal performance in young adults and similar levels of underperformance in children and older adults. However, similarities in children and older adults might conceal differences in underlying control processes. We mapped out age-related differences in postural control using center-of-pressure trajectories of 299 participants ranging from 7 to 81 years old in three tasks: stable stance, compromised vision, and narrowed base of support. Summary statistics (path length, ellipse area) replicated the well-known U-shape function also showing that compromising vision and narrowing the base of support affected older adults more than children. Stabilogram diffusion analysis (SDA) allows to assess postural control performance in terms of diffusion at short (< 1 s) and longer timescales. SDA parameters showed the strongest short-term drift in older adults, especially under compromised vision or narrowed base of support conditions. However, older adults accommodated their poor short-term control by corrective adjustments as reflected in long-term diffusion under eyes closed conditions and initiating anti-persistent behavior earlier compared with children and young adults in tandem stance. We argue that these results highlight the adaptability of the postural control system and warrant a reinterpretation of previous postural control frameworks.

Postural Control of Patients with Low Back Pain Under Dual-Task Conditions.

Low back pain is a major global public health problem, but the current intervention effect is not ideal. A large body of previous literature suggests that patients with chronic low back pain may have abnormal postural control, which is more evident in the dual task situation. In recent years, research on postural control in patients with low back pain under dual-task conditions has gradually become a hot topic. However, the results obtained from these studies were not entirely consistent. In this review, we summarized relevant studies on the performance of postural control in patients with low back pain under dual-task conditions, analyze it from the perspective of the theoretical model of dual-task interaction, the specific research paradigm of dual task, the performance of postural control, and the related factors affecting postural control performance, etc. It was reasonable to assume that patients with low back pain might have a certain degree of abnormal postural control, and this abnormality was affected by comprehensive factors such as age, cognitive resource capacity, attention needs, complex sensorimotor integration, external environment, etc. Furthermore, postural control performance in low back pain patients under dual-task conditions was further influenced by the nature and complexity of the different tasks. In general, the more attention resources were needed, the external environmental conditions were worse, and the age-related functions were degenerate, etc., the weaker posture control ability was. In short, a deeper understanding of postural control in patients with low back pain under dual-task conditions may shed light on more references for the rehabilitation and management of low back pain, as well as some new ideas for scientific research on cognition and postural control.

Priming Effects of Anodal Transcranial Direct Current Stimulation on the Effects of Conventional Physiotherapy on Balance and Muscle Performance in Athletes With Anterior Cruciate Ligament Injury.

In athletes, postural control impairment and knee muscle dysfunction are the most common disorders following anterior cruciate ligament (ACL) injury. Because of functional changes in the motor cortex following ACL injury, physiotherapy (PT) is not enough for treatment and using neuromodulators, such as trans-cranial direct current stimulation (tDCS) may be necessary. The present study focused on the effects of anodal tDCS (a-tDCS) over the primary motor cortex (M1) concurrent with PT on postural control and muscular performance in the athletes with ACL injury. In this study, 34 athletes with ACL injury were randomly assigned in 2 groups of intervention group (active M1 a-tDCS concurrent with PT, n = 16) and control group (sham M1 a-tDCS concurrent with PT, n = 16). The participants of all groups received 20-minute 2 mA M1 a-tDCS with PT during 10 sessions, while tDCS was turned off after 30 seconds in the sham group. Before, immediately following, and 1 month after the interventions, the center of pressure and the average of power of flexor and extensor muscles at 2 velocities of 30°/s and 60°/s were measured by force plate and isokinetic devices, respectively. One month after treatment, the displacement of center of pressure was decreased in the intervention group (P < .05), while there were no changes in the control group. Y-axis of center of pressure decreased in the intervention group relative to the control group, although average of power of flexor and extensor muscles increased immediately in both groups, but the rise in the intervention group was larger than that in the control group (P < .05). The findings indicated that M1 a-tDCS can induce the efficacy of PT, which has a lasting effect on the improvement of the postural control in athletes with ACL injury.

Effectiveness of proprioceptive training in athletes with and without ankle instability: systematic review

Background: The proprioceptive program is directly related to neuromuscular control, which uses proprioceptive afferences to provide dynamic stabilization of the joint. Some variables can be considered risk factors for injuries, such as sprains, sudden and unexpected movement activities, simple quick changes of direction, soil type or footwear, among others. The balance training program contributes to lower injury rates and increases sports performance rate. Thus works the perception and maintenance of postural balance from information coming from sensory afferences. Objective: To perform a systematic review and verify the effect of proprioceptive training on ankle joint in athletes. Methods: A search for clinical trials was performed in the PUBMED, WEB OF SCIENCE, PEdro and SCIELO databases, the terms used for the search were “Proprioception”, “Athletic” and “Rehabilitation”, with the filters: articles published between the years of 2015 to 2020 and research in humans. Only studies published in the English language that addressed the proposed theme were included. The PEDro scale was used to evaluate the quality of studies with clinical trials, where studies with a score lower than 6/10 on the scale were excluded. Results: With the search 69 articles were found, removing the duplicates we obtained 67 eligible articles, of these, 15 studies met the inclusion and exclusion criteria. After complete analysis, 9 studies were included. Conclusion: Proprioceptive training in athletes, lasting at least three weeks with weekly protocols composed of dynamic exercises directed at individuals with ankle instability is totally effective for both joint injury prevention and rehabilitation. In addition to the increase of variables such as postural balance, coordination, postural control and functional performance.

Stationary rehabilitation robot and functional electrostimulation for the treatment of patients in the initial six months after stroke: a randomized controlled trial

Background: Results from studies investigating the effects of rehabilitation robots, including those using robots combined with functional electrostimulation (FES), on gait quality and postural control post-stroke are conflicting. Therefore, the evidence supporting the use of this approach to rehabilitation remains inconclusive and further research is required into how robotic therapy and FES can improve gait function and postural control at different times after stroke. Aim of the study: To gain knowledge on the effectiveness of stationary robotic exercises, and robotic exercises combined with FES of the lower extremity muscles, on activities of daily living, gait quality, postural control, and quality of life, in people who were between one and six months post-stroke. Material and Methods: A randomized controlled clinical pilot study was conducted. Forty-three post-stroke patients hospitalized at a rehabilitation center were randomly assigned to the following three groups: the GEO Group, for whom stationary robotic exercises were provided, the GEO+FES Group, for whom stationary robotic exercises were provided in combination with FES, and the Control Group, for whom conventional overground gait training was provided. Exercises were undertaken by all groups for 20 minutes a day, six days a week, for three weeks. In addition, all patients were provided with basic post-stroke therapy based on the principles of best clinical practice. All patients were assessed for stroke symptoms before and after therapy using the National Institutes of Health Stroke Scale (NIHSS), for independence in activities of daily living using the Barthel Index, and for quality of life using the Stroke Impact Scale Questionnaire. Static and dynamic postural control and gait performance were assessed using the Berg Balance Scale, the Timed Up and Go Test, the Functional Reach Test, and the 10 Meter Walk Test. Static postural control and gait quality were also assessed using a treadmill with a stabilometric platform. Results. Exercising on a stationary robot, both with and without FES of the lower extremity muscles, contributed to a statistically significant reduction in stroke symptoms (NIHSS, p&lt;0.05). Additionally, exercising on a stationary robot without FES application significantly improved patient quality of life (p&lt;0.05). However, these effects were not significantly different between the experimental and control groups. Conclusions. Stationary robotic exercise, either with or without FES, can be used as a substitute for traditional overground gait training to reduce stroke symptoms and improve quality of life in the first six months post-stroke. They can also be used as exercises to augment standard post-stroke therapy.

Does 8Weeks of Integrated Functional Core and Plyometric Training Improve Postural Control Performance in Young Rhythmic Gymnasts?

It has been suggested that core stability and plyometric training(CPT) can enhance athletes' postural control. Nevertheless, the effects of an integrated core and plyometric training program on rhythmic gymnastics (RG) performance are unclear. This study aimed to evaluate the effects of an integrated functional CPT program on young rhythmics gymnasts' postural performance. A sample of 44 young female rhythmic gymnasts from a competitive team (age = 10.5 ± 1.8years) participated in the study. The subjects were randomly divided into a control group and an experimental group. Pre- and posttest design was used. Postural control was assessed using single-leg stance tests and RG-specific balances over a force platform and evaluated by expert RG judges. The experimental group (n = 23) completed an 8-week functional CPT program based on RG technical requirements. Meanwhile, the control group (n = 21) received their usual training sessions. A mixed model of analysis of variance was applied to evaluate the effects of an intrasubject factor and an intersubject factor on each of the dependent variables. After 8weeks, the experimental group obtained significant better results in some variables of the right support leg with eyes open and left support leg with eyes open single-leg support (p < .01), improvements were also found in some specific RG balances: Arabesque measured on the force platform (p < .01) and the side leg with help balance scored by the judges (p < .01). In conclusion, an integrated functional CPT program improved postural control in young rhythmic gymnasts. Coaches should consider using this CPT to improve RG performance.

Relationship between physical activity level and sleep quality with postural control and hemodynamic response in the prefrontal cortex during dual-task performance

Understanding the cortical activation and postural control behavior during dual-task (DT) has been an object of study. However, despite the multiple benefits of exercise and good sleep quality, less is known about the correlation between physical activity (PA) and sleep quality (SQ) on postural control and brain activation under dual-task performance. This study aimed to analyze the correlation between PA level and SQ with postural control performance and hemodynamic response in the prefrontal cortex during the DT performance in young adults. Thirty-four healthy young adults (mean age ± SD = 22.91 ± 3.90 years) participated in this study, and they performed a single-task and cognitive and motor DT using their smartphones. Postural control was assessed using a force plate to record the center of pressure (CoP) data (total excursion of CoP (TOTEX CoP), displacements of the CoP in anterior-posterior (CoP-AP) and medial-lateral (CoP-ML) directions, mean total velocity displacement of CoP (MVELO CoP), mean displacement velocity of CoP in anterior-posterior (MVELO CoP-AP) and medial-lateral (MVELO CoP-ML) directions, amplitude of CoP in anterior-posterior (A-AP) and medial-lateral (A-ML) directions, and 95% confidence ellipse sway area (CEA)). The hemodynamic response was measured by the oxyhemoglobin and deoxyhemoglobin concentrations using the functional near-infrared spectroscopy. The Pittsburg Sleep Quality Index and International Physical Activity Questionnaire-Short Form questionnaires assessed SQ and level of PA, respectively. Results indicated a positive correlation between SQ and cognitive DT cost for CoP-ML (rs = 0.422, p = 0.013), MVELO CoP-ML (rs = 0.422, p = 0.013) and A-ML (rs = 0.579, p < 0.001). There were no significant relations between the other outcomes (p > 0.05). In conclusion, poor sleep quality was associated with a worse postural control performance in CoP-ML, MVELO CoP-ML and A-ML parameters under cognitive dual-task conditions. The differences found in the postural control and hemodynamic response during dual-task performance do not correlate with physical activity level.

The role of pain intensity and depressive symptoms in the relationship between sleep quality and postural control among middle-aged and older adults with Fibromyalgia

Objective Fibromyalgia (FM) is a chronic pain condition often accompanied by sleep problems and depression that are each associated with reduced physical ability including postural control. Research supports a sequential association between pain intensity and depression in FM, and poor sleep quality may play a key role in this relationship. This study aimed to verify a serial pattern of associations among sleep quality, pain intensity, and depressive symptoms and quantify these effects on objective postural control. Design Community-residing adults diagnosed with FM (n = 155; Mage = 61.08, SD = 7.70; 93% female; 79% White) were included in this cross-sectional study. Main outcomes Participants self-rated sleep quality (restorative sleep, sleep waking, and sleep latency), pain intensity, and depressive symptoms, and the Fullerton Advanced Balance (FAB) scale and 8-Foot Up and Go Test (8FUPGT) measured objective postural control. Results Findings indicated that the serial association between pain intensity and depressive symptoms fully mediated the relationship between sleep quality and both FAB (95% CI [-.125, -.013]), and 8FUPGT (95% CI [.002, .033]) performance. Conclusion Findings highlight the serial association of pain intensity and depressive symptoms with objective postural control performance and the potential for sleep and depression interventions that may maximize functional outcomes in FM.

Investigation of postural control and spatiotemporal parameters of gait during dual tasks in ataxic individuals

Concurrent cognitive and motor tasks in ataxic individuals cause functional limitations and negatively affect the independence of patients in daily life. This study aimed to examine the effects of dual task on postural control and spatiotemporal parameters of gait in ataxic individuals. The study included 20 individuals with ataxia. Disease severity was evaluated using the International Cooperative Ataxia Rating Scale. A force platform was used to evaluate postural sway and limits of stability and a GAITRite electronic walkway to evaluate the spatiotemporal parameters of gait. Postural control and gait were evaluated without a simultaneous task (task-1) and with dual tasks consisting of counting the names starting with "a selected letter such as A" (task-2), counting backwards aloud in threes from 100 (task-3), carrying a glass of water with a tray (task-4), and speaking on a mobile phone (task-5). The effects of dual task on postural control and gait parameters were examined with multiple comparisons. The tasks requiring cognitive skills (tasks 2, 3, 5) were determined to have a greater effect on the increase of body sway, and gait was seen to be affected by motor and/or cognitive tasks (tasks 2, 4, 5). From the results of the present study, it is thought that evaluations of postural control and gait performance of ataxic individuals together with the dual tasks they may encounter in daily life are important in terms of their independence in activities of daily living.

Parameters uncertainty analysis of posture control of a four-wheel-legged robot with series slow active suspension system

This paper focuses on the posture control performance on uneven terrain for a wheel-legged robot (WLR). Firstly, a novel four-wheel-legged robot (FWLR) with series slow active suspension system (SSASS) is proposed. Secondly, the parameters uncertainty of posture control is studied, and an 11 DOF dynamic model and the corresponding system state equation are presented. Thirdly, to suppress the chattering problem and enhance the robustness of traditional sliding mode controller (TSMC), the second order low-pass filter (SOLPF), equivalent speed control, saturation function, terrain estimation model and the actuator model are introduced into the control system, and an improved sliding mode controller (ISMC) is proposed. Finally, both the co-simulation and experiment on uneven terrain are carried out, the results show that even if the system parameters have 30% variation, the robot posture angle can be improved effectively. That is, the proposed robot and ISMC control strategy have good posture control performance with low parameters sensitivity on uneven terrain. Overall, this paper attempts to provide an effective way for the application of WLR on uneven terrain.

Effects of 4Weeks of High-Definition Transcranial Direct Stimulation and Foot Core Exercise on Foot Sensorimotor Function and Postural Control.

Objective: This study aimed to examine the effects of 4 weeks of high-definition transcranial direct current stimulation (HD-tDCS) and foot core exercise (FCE) on foot sensorimotor function (i.e., toe flexor strength and passive ankle kinesthesia) and postural control. Methods: In total, 36 participants were randomly assigned into three groups as follows: HD-tDCS, FCE, and the control group. A total of 12 training sessions were performed over 4 weeks (i.e., three sessions per week) in the laboratory. The HD-tDCS group received 20-min HD-tDCS with a current density of 2 mA, and the FCE group completed short foot exercise, towel curls, toe spread and squeeze, and balance board training. Participants in the control group just maintained the activities what they usually did and did not receive any interventions. Foot muscle strength, passive ankle kinesthesia, and postural control were assessed at baseline and post-intervention. Results: HD-tDCS induced a greater decrease in the percentage changes in the passive kinesthesia thresholds of ankle inversion (p < 0.001) and eversion (p = 0.013) than the control group. Compared with the control group, a significant increase in the percentage change in the metatarsophalangeal joint flexor strength was found in the HD-tDCS group (p = 0.008) and the FCE group (p = 0.027), and a significant increase in the percentage change in toe flexor strength was observed in the FCE group (p = 0.015). Moreover, FCE induced a greater reduction in the percent changes in the medial–lateral average center of gravity sway velocity in one-leg standing with eyes open (p = 0.033) and the anteroposterior average center of gravity sway velocity in one-leg standing with eyes closed (p < 0.001) than control. Conclusion: This study demonstrated that 4 weeks of HD-tDCS and FCE induced distinct benefits on foot sensorimotor function and the standing postural control performance in healthy young adults. HD-tDCS could improve the metatarsophalangeal joint flexor strength and the passive kinesthesia thresholds of ankle inversion and eversion. Meanwhile, FCE could also enhance foot muscle strength and enhance postural control performance in one-leg standing.