The relative contributions of proprioceptive, vestibular, and visual sensory cues to balance control change depending on their availability and reliability. This sensory reweighting is classically supported by non-linear sway responses to increasing visual surround and/or surface tilt amplitudes. However, recent evidence indicates that visual cues are reweighted based on visual tilt velocity rather than tilt amplitude. Therefore, we designed a study to specifically test the hypothesized velocity dependence of reweighting while expanding on earlier findings for visual reweighting by testing proprioceptive reweighting for standing balance on a tilting surface. Twenty healthy young adults stood with their eyes closed on a toes-up/-down tilting platform. We designed four pseudo-random tilt sequences with either a slow (S) or a fast (F) tilt velocity and different peak-to-peak amplitudes. We used model-based interpretations of measured sway characteristics to estimate the proprioceptive sensory weight (Wprop) within each trial. Additionally, root-mean-square values of measured body centre of mass sway amplitude (RMS) and velocity (RMSv) were calculated for each tilt sequence. Wprop, RMS, and RMSv values varied depending on the stimulus velocity, exhibiting large effects (all Cohen\'s d\'s > 1.10). In contrast, we observed no significant differences across stimulus amplitudes for Wprop (Cohen\'s d\'s: 0.02-0.16) and, compared to the differences in velocity, there were much smaller changes in RMS and RMSv values (Cohen\'s d\'s: 0.05 - 0.91). These results confirmed the hypothesized velocity, rather than amplitude, dependence of sensory reweighting.

Ageing induces a decline in GABAergic intracortical inhibition, which seems to be associated not only with decremental changes in well-being, sleep quality, cognition and pain management but also with impaired motor control. So far, little is known regarding whether targeted interventions can prevent the decline of intracortical inhibition in the primary motor cortex in the elderly. Therefore, the present study investigated whether age-related cortical dis-inhibition could be reversed after 6 months of balance learning and whether improvements in postural control correlated with the extent of reversed dis-inhibition. The results demonstrated that intracortical inhibition can be upregulated in elderly subjects after long-term balance learning and revealed a correlation between changes in balance performance and intracortical inhibition. This is the first study to show physical activity-related upregulation of GABAergic inhibition in a population with chronic dis-inhibition and may therefore be seminal for many pathologies in which the equilibrium between inhibitory and excitatory neurotransmitters is disturbed. KEY POINTS: Ageing induces a decline in GABAergic intracortical inhibition. So far, little is known regarding whether targeted interventions can prevent the decline of intracortical inhibition in the primary motor cortex in the elderly. After 6 months of balance learning, intracortical inhibition can be upregulated in elderly subjects. The results of this study also revealed a correlation between changes in balance performance and intracortical inhibition. This is the first study to show physical activity-related upregulation of GABAergic inhibition in a population with chronic dis-inhibition.

For some individuals with severe socket-related problems, prosthesis osseointegration directly connects a prosthesis to the residual limb creating a bone-anchored limb (BAL). We compared dynamic gait stability and between-limb stability symmetry, as measured by the Margin of Stability (MoS) and the Normalized Symmetry Index (NSI), for people with unilateral transfemoral amputation before and one-year after BAL implantation. The MoS provides a mechanical construct to assess dynamic gait stability and infer center of mass and limb control by relating the center of mass and velocity to the base of support. Before and one-year after BAL implantation, 19 participants walked overground at self-selected speeds. We quantified dynamic gait stability anteriorly and laterally at foot strike and at the minimum lateral MoS value. After implantation, we observed decreased lateral MoS at foot strike for the amputated (MoS mean(SD) %height; pre: 6.6(2.3), post: 5.9(1.3), d = 0.45) and intact limb (pre: 6.2(1.2), post: 5.8(1.0), d = 0.38) and increased between-limb MoS symmetry at foot strike (NSI mean(SD) %; anterior-pre: 10.3(7.3), post: 8.4(3.6), d = 0.23; lateral-pre: 18.8(12.4), post: 12.4(4.9), d = 0.47) and at minimum lateral stability (pre: 28.1(18.1), post: 19.2(6.8), d = 0.50). Center of mass control using a BAL resulted in dynamic gait stability more similar between limbs and may have reduced the adoption of functional asymmetries. We suggest that improved between-limb MoS symmetry after BAL implantation is likely due to subtle changes in individual limb MoS values at self-selected walking speeds resulting in an overall positive impact on fall risk through improved center of mass and prosthetic limb control.

BACKGROUND: Sensory information obtained from the visual, somatosensory, and vestibular systems is responsible for regulating postural control, and if damage occurs in one or more of these sensory systems, postural control may be altered.
OBJECTIVE: To evaluate and compare the postural sway velocity between children with normal hearing and with sensorineural hearing loss (SNHL), matched by sex and age group, and to compare the postural sway velocity between children with normal hearing and with SNHL, with and without vestibular dysfunction.
METHODS: Cross-sectional study that evaluated 130 children (65 with normal hearing and 65 with SNHL), of both sexes and aged between 7 and 11 years, from public schools of the city of Caruaru, Pernambuco state, Brazil. The postural sway velocity of the center of pressure (COP) was assessed by a force platform, in two directions, anteroposterior (AP) and mediolateral (ML)), in three positions, namely bipedal support with feet together and parallel (parallel feet (PF)), bipedal support with one foot in front of the other (tandem foot (TF)), and single-leg support (one foot (OF)), evaluated with the eyes open and closed.
RESULTS: Children with SNHL demonstrated greater postural sway velocity compared to children with normal hearing in all the positions evaluated, with significant differences in the AP direction, with the eyes open (PF: p = 0.001; TF: p = 0.000; OF: p = 0.003) and closed (PF: p = 0.050; TF: p = 0.005). The same occurred in the ML direction, with the eyes open (PF: p = 0.001; TF: p = 0.000; OF: p = 0.001) and closed (PF: p = 0.002; TF: p = 0.000). The same occurred in relation to vestibular function, where the children with SNHL with an associated vestibular dysfunction demonstrated greater postural sway velocity compared to children with normal hearing in all the positions evaluated, demonstrating significant differences in the AP direction, with the eyes open (TF: p = 0.001; OF: p = 0.029) and eyes closed (PF: p = 0.036; TF: p = 0.033). The same occurred in the ML direction, with the eyes open (TF: p = 0.000) and with the eyes closed (PF: p = 0.008; TF: p = 0.009).
CONCLUSIONS: Children with SNHL demonstrated greater instability of postural control than children with normal hearing in all the directions assessed. Children with SNHL and an associated vestibular dysfunction demonstrated the greatest instability of postural control in this study.

Noninvasive tracking devices are widely used to monitor real-time posture. Yet significant potential exists to enhance postural control quantification through walking videos. This study advances computational science by integrating OpenPose with a Support Vector Machine (SVM) to perform highly accurate and robust postural analysis, marking a substantial improvement over traditional methods which often rely on invasive sensors. Utilizing OpenPose-based deep learning, we generated Dynamic Joint Nodes Plots (DJNP) and iso-block postural identity images for 35 young adults in controlled walking experiments. Through Temporal and Spatial Regression (TSR) models, key features were extracted for SVM classification, enabling the distinction between various walking behaviors. This approach resulted in an overall accuracy of 0.990 and a Kappa index of 0.985. Cutting points for the ratio of top angles (TAR) and the ratio of bottom angles (BAR) effectively differentiated between left and right skews with AUC values of 0.772 and 0.775, respectively. These results demonstrate the efficacy of integrating OpenPose with SVM, providing more precise, real-time analysis without invasive sensors. Future work will focus on expanding this method to a broader demographic, including individuals with gait abnormalities, to validate its effectiveness across diverse clinical conditions. Furthermore, we plan to explore the integration of alternative machine learning models, such as deep neural networks, enhancing the system\'s robustness and adaptability for complex dynamic environments. This research opens new avenues for clinical applications, particularly in rehabilitation and sports science, promising to revolutionize noninvasive postural analysis.

Body-machine interfaces (BoMIs)-systems that control assistive devices (e.g., a robotic manipulator) with a person\'s movements-offer a robust and non-invasive alternative to brain-machine interfaces for individuals with neurological injuries. However, commercially-available assistive devices offer more degrees of freedom (DOFs) than can be efficiently controlled with a user\'s residual motor function. Therefore, BoMIs often rely on nonintuitive mappings between body and device movements. Learning these mappings requires considerable practice time in a lab/clinic, which can be challenging. Virtual environments can potentially address this challenge, but there are limited options for high-DOF assistive devices, and it is unclear if learning with a virtual device is similar to learning with its physical counterpart. We developed a novel virtual robotic platform that replicated a commercially-available 6-DOF robotic manipulator. Participants controlled the physical and virtual robots using four wireless inertial measurement units (IMUs) fixed to the upper torso. Forty-three neurologically unimpaired adults practiced a target-matching task using either the physical (sample size n = 25) or virtual device (sample size n = 18) involving pre-, mid-, and post-tests separated by four training blocks. We found that both groups made similar improvements from pre-test in movement time at mid-test (Δvirtual: 9.9 ± 9.5 s; Δphysical: 11.1 ± 9.9 s) and post-test (Δvirtual: 11.1 ± 9.1 s; Δphysical: 11.8 ± 10.5 s) and in path length at mid-test (Δvirtual: 6.1 ± 6.3 m/m; Δphysical: 3.3 ± 3.5 m/m) and post-test (Δvirtual: 6.6 ± 6.2 m/m; Δphysical: 3.5 ± 4.0 m/m). Our results indicate the feasibility of using virtual environments for learning to control assistive devices. Future work should determine how these findings generalize to clinical populations.

This study examined the differences between children and adolescents with autism spectrum disorder (ASD) and neurotypically developing (NTD) in terms of balance, postural control, and motor skills. It also examined which motor skills are most affected and whether scores on different assessment tests in ASD children are correlated. A cross-sectional observational study with two research groups was conducted. Timed up and go test (TUG), short form of Bruininks-Oseretsky test of Motor Proficiency version 2 (SFBOT-2), and pediatric balance scale (PBS) were used. A total of 100 participants 50 with ASD and 50 with NTD engaged in the research. Statistically significant differences were obtained between control group and ASD group in TUG test and in SFBOT-2 standard score and total score (p-value = <0.01). A statistically significant difference (p-value = <0.01) was seen between ASD group\'s and control group\'s PBS scores. Poor correlation was noted between TUG and SFBOT-2, as well as between PBS and TUG. A moderate correlation was also found between SFBOT-2 and PBS. Children with ASD present difficulties in motor skills and in static and dynamic balance compared to children with NTD. Differences were observed in the motor skills of strength followed by manual dexterity, running speed and agility, fine motor precision, fine motor integration, and balance. The PBS item that showed the greatest difference between the ASD group and control group was maintaining monopodial support with hands on hips. Finally, poor to moderate correlations were obtained between the different tests with statistically significant differences.

OBJECTIVE: To identify causes of balance impairment in children undergoing treatment for cancer and childhood cancer survivors.
METHODS: A systematic search was performed according to PRISMA guidelines. Studies were included if participants were 0-19 years of age with a current/past diagnosis of cancer, an objective balance measure was reported, and a cause of balance impairment was either stated or implied.
RESULTS: The 64 full text studies included identified balance impairments as sequelae secondary to CNS tumors, and/or as an effect of medical treatment including chemotherapy, radiation, and/or surgery. Cancer treatment can result in damage to the visual, vestibular and/or somatosensory systems which in turn can contribute to balance dysfunction.
CONCLUSIONS: Balance impairments were caused by the cancer itself or the result of medical treatment. Oncology professionals are integral in recognition and treatment of factors affecting balance impairments in childhood cancer; however, further research is needed to identify interventions targeting specific causes of balance impairment.

Nonlinear analyses have emerged as an approach to unraveling the intricate dynamics and underlying mechanisms of postural control, offering insights into the complex interplay of physiological and biomechanical factors. However, achieving a comprehensive understanding of the application of nonlinear analysis in postural control studies remains a challenge due to the various nonlinear measurement methods currently available. Thus, this scoping review aimed to identify existing nonlinear analyses used to study postural control in both dynamic and quiet tasks, and to summarize and disseminate the available literature on the use of nonlinear analysis in postural control. For this purpose, a scoping review was conducted and reported following the PRISMA Extension for Scoping Reviews (PRISMA-ScR) Checklist and Explanation. Searches were conducted up to July 2023 on PubMed/Medline, Embase, CINAHL, Web of Science, and Google Scholar databases, resulting in the inclusion of 397 unique studies. The main classes employed among the studies were entropy-based, fractal-based, quantification of recurrence plots, and quantification of stability, with a total of 91 different algorithms distributed among these classes. The most common condition used to study postural control was quiet standing, followed by dynamic standing and gait tasks. Although various algorithms were utilized for this purpose, sample entropy was employed in 43% of studies to explore mechanisms related to postural control. Among them, 28% were in quiet standing, 3.27% were in dynamic standing, and 4.78% to study postural control during the gait. The results also provide insights into nonlinear analysis for future studies, concerning the complexity and interactions within the postural control system across various task demands.

OBJECTIVE: To describe hand grip strength, walking speed, functional mobility, and postural control at one year following intensive care unit admission for COVID-19, and to find any predictors that are associated with impaired hand grip strength, walking speed, functional mobility, or postural control at the 1-year follow-up.
METHODS: Retrospective cross-sectional and longitudinal observational study.
METHODS: Intensive care unit and outpatient research clinic at Sahlgrenska University Hospital.
METHODS: Of the 105 individuals in \"The Gothenburg Recovery and Rehabilitation after COVID-19 and Intensive Care Unit\" cohort, 78 participated in this study.
METHODS: Descriptive statistics for hand grip strength, walking speed, functional mobility, and postural control were presented and binary logistic regressions were performed to find their significant predictors.
RESULTS: At 1-year following intensive care unit admission for COVID-19, impaired hand grip strength was found in 24.4% for the right hand and 23.1% for the left hand. Walking speed, functional mobility, and postural control were found to be impaired in 29.5%, 21.8%, and 5.1%, respectively. For impaired walking speed, longer length of stay at intensive care unit and presence of diabetes mellitus were risk factors. Diabetes mellitus was found to be the risk factor for impaired functional mobility.
CONCLUSIONS: In this study, 45% of the participants showed impairment in function, activity capacity or both. These results suggest that individuals who recovered after intensive care unit admission for COVID-19 would benefit from receiving long-term follow-up to enable identification of those with need of physical health assistance and rehabilitation.