Effects of arousal and valence on center of pressure and ankle muscle activity during quiet standing.

Emotion affects postural control during quiet standing. Emotional states can be defined as two-dimensional models comprising valence (pleasant/unpleasant) and arousal (aroused/calm). Most previous studies have investigated the effects of valence on postural control without considering arousal. In addition, studies have focused on the center of pressure (COP) trajectory to examine emotional effects on the quiet standing control; however, the relationship between neuromuscular mechanisms and the emotionally affected quiet standing control is largely unknown. This study aimed to investigate the effects of arousal and valence on the COP trajectory and ankle muscle activity during quiet standing. Twenty-two participants were instructed to stand on a force platform and look at affective pictures for 72 seconds. The tasks were repeated six times, according to the picture conditions composed of arousal (High and Low) and valence (Pleasant, Neutral, and Unpleasant). During the task, the COP, electromyogram (EMG) of the tibialis anterior and soleus muscles, and electrocardiogram (ECG) were recorded. The heart rate calculated from the ECG was significantly affected by valence; the value was lower in Unpleasant than that in Neutral and Pleasant. The 95% confidence ellipse area and standard deviation of COP in the anterior-posterior direction were lower, and the mean power frequency of COP in the anterior-posterior direction was higher in Unpleasant than in Pleasant. Although the mean velocity of the COP in the medio-lateral direction was significantly lower in Unpleasant than in Pleasant, the effect was observed only when arousal was low. Although the EMG variables were not significantly affected by emotional conditions, some EMG variables were significantly correlated with the COP variables that were affected by emotional conditions. Therefore, ankle muscle activity may be partially associated with postural changes triggered by emotional intervention. In conclusion, both valence and arousal affect the COP variables, and ankle muscle activity may be partially associated with these COP changes.

Effects of active exergames on physical performance in older people: an overview of systematic reviews and meta-analysis.

This overview assessed the available body of published peer-reviewed systematic reviews and meta-analyses related to the effects of active exergames compared with active/passive control on physical performance outcomes in older people. The methodological quality and certainty of evidence were assessed using PRISMA, AMSTAR 2, and GRADE. The protocol was registered in PROSPERO (code: CRD42023391694). The main outcomes indicate that 4,477 records, five systematic reviews, and 10 meta-analyses were included. The AMSTAR-2 reported six meta-analyses with high methodological quality, four moderate quality, two systematic reviews with low quality, and three very-low quality. Meta-analysis was performed on balance using the Berg Balance Scale (BBS) and Timed Up-and-Go (TUG) tests, on cardiorespiratory fitness using the 6-min walk test, and on upper and lower limbs muscle strength using the handgrip strength, knee extension, and 30-s chair stand tests. Significant differences in favor of the active exergames groups concerning active/passive groups were reported in BBS (SMD = 0.85; 95% CI = 0.12-1.58; I2 = 96%; p = 0.02), TUG (SMD = 1.44; 95% CI = 0.71-2.16; I2 = 97%; p < 0.0001), and 30-s chair stand test (SMD = 0.79; 95% CI = 0.33-1.25; I2 = 88%; p = 0.0008). However, no significant differences were reported in favor of the active exergames groups in 6-min walk (SMD = 0.93; 95% CI = -0.64 to 2.50; I2 = 95%; p = 0.24), handgrip strength (SMD = 0.67; 95% CI = -0.04 to 1.38; I2 = 84%; p = 0.06), and knee extension tests (SMD = 0.20; 95% CI = -0.05 to 0.44; I2 = 95%; p = 0.12) compared to active/passive control. However, it was impossible to perform a meta-analysis for the variables of walking speed as a fall risk due to the diversity of instruments and the small number of systematic reviews with meta-analysis. In conclusion, interventions utilizing active exergames have shown significant improvements in the static and dynamic balance and lower limb muscle strength of apparently healthy older people, compared to control groups of active/inactive participants, as measured by BBS, TUG, and 30-s chair stand tests. However, no significant differences were found in the 6-min walk, HGS, and knee extension tests. Systematic review registration: PROSPERO, CRD42023391694.

Community integration and its predictors in people with stroke: a multicenter longitudinal study.

OBJECTIVE: To investigate the community integration of patients following stroke and determine the predictors of their level of community integration at 1-year follow-up. DESIGN: A multicenter, longitudinal, and observational study. SUBJECTS: Sixty-five inpatients (41 men) with a mean age of 56.9 (standard deviation = 17.0) years, who had their first stroke at least 1 month prior to this study were recruited from 4 rehabilitation inpatient wards in China. METHODS: In the initial assessment, the participants were evaluated using the Community Integration Questionnaire, the Fugl-Meyer Assessment, the Berg Balance Scale, the Modified Barthel Index, the Mini Mental State Examination, and the Modified Ashworth Scale. In the follow-up assessments, which were conducted via telephone no less than 1 year after discharge, the participants were evaluated using the Community Integration Questionnaire and also assessed for other disease-related conditions. RESULTS: The participants' scores on the Community Integration Questionnaire in the follow-up assessment were significantly greater than those at the initial assessment (p < 0.05). In addition, the participants' Community Integration Questionnaire scores in the follow-up assessment were significantly correlated with their ages, numbers of years of education, and Modified Barthel Index, Berg Balance Scale, Mini Mental State Examination scores in the initial assessment (p < 0.05), and marginally significantly correlated with their scores on Fugl-Meyer Assessment in the initial assessment (p = 0.058). The participants' ages, numbers of years of education, and Modified Barthel Index, Berg Balance Scale, Mini Mental State Examination, Fugl-Meyer Assessment of the lower extremity, and Fugl-Meyer Assessment scores in the initial assessment were predictive of their Community Integration Questionnaire scores at follow-up, with coefficients of determination ranging from 0.254 to 0.056 (p < 0.05). CONCLUSIONS: The level of community integration of the participants was generally low, but it was greater at 1-year follow-up than it was initially. Balance function and daily living ability may be key predictors of community integration of patients following stroke.

A comprehensive multivariate analysis of the center of pressure during quiet standing in patients with Parkinson's disease.

BACKGROUND: We hypothesized that postural instability observed in individuals with Parkinson's disease (PD) can be classified as distinct subtypes based on comprehensive analyses of various evaluated parameters obtained from time-series of center of pressure (CoP) data during quiet standing. The aim of this study was to characterize the postural control patterns in PD patients by performing an exploratory factor analysis and subsequent cluster analysis using CoP time-series data during quiet standing. METHODS: 127 PD patients, 47 aged 65 years or older healthy older adults, and 71 healthy young adults participated in this study. Subjects maintain quiet standing for 30 s on a force platform and 23 variables were calculated from the measured CoP time-series data. Exploratory factor analysis and cluster analysis with a Gaussian mixture model using factors were performed on each variable to classify subgroups based on differences in characteristics of postural instability in PD. RESULTS: The factor analysis identified five factors (magnitude of sway, medio-lateral frequency, anterio-posterior frequency, component of high frequency, and closed-loop control). Based on the five extracted factors, six distinct subtypes were identified, which can be considered as subtypes of distinct manifestations of postural disorders in PD patients. Factor loading scores for the clinical classifications (younger, older, and PD severity) overlapped, but the cluster classification scores were clearly separated. CONCLUSIONS: The cluster categorization clearly identifies symptom-dependent differences in the characteristics of the CoP, suggesting that the detected clusters can be regarded as subtypes of distinct manifestations of postural disorders in patients with PD.

Assessing Cognitive Effort in Ménière's Disease: Pupillometry as a Novel Tool for Postural Control.

BACKGROUND: This study aimed to investigate the utility of pupillometry as a measure of cognitive effort in individuals with Ménière's disease experiencing chronic postural destabilization. By integrating pupillometry with static posturography, we sought to gain deeper insights into the cognitive demands and arousal levels associated with postural control in this specific patient population. METHODS: The study included 36 patients who met the diagnostic criteria for Ménière's disease and a control group comprising 36 healthy volunteers. We performed static posturography using a computerized static posturography platform to objectively assess postural imbalance. Additionally, pupillometry was recorded using infrared video-oculoscopy. Pupil dilation was measured before and after participants walked for 7 steps on-site with their vision obscured. RESULTS: Baseline tonic pupil size showed no significant difference between healthy controls and Ménière's patients. However, after walking stimulation, Ménière's patients exhibited highly significant abnormal walking-induced pupil dilation. This suggests increased arousal in response to the challenging task of walking with closed eyes, linked to static upright stance imbalance as correlated with posturography parameters. CONCLUSION: Pupillometry holds promise as an objective tool to assess cognitive effort and arousal during postural control in Ménière's disease. Implementing pupillometry in clinical practice could enhance the management of postural instability in these patients. Our findings contribute to the understanding of cognitive aspects in balance control and open new avenues for further investigations in vestibular dysfunction.

Effects of a nighttime melatonin ingestion on dynamic postural balance and muscle strength the following morning in people living with multiple sclerosis: A preliminary study.

BACKGROUND: Decreased endogenous melatonin concentrations in people with multiple sclerosis (PwMS) are associated with fatigue and pain that impair postural balance and muscle strength. Melatonin ingestion had analgesic and anti-fatigue effects. However, the acute effect of exogenous melatonin on dynamic postural stability and muscle strength has not been studied yet in PwMS. This study aimed to investigate the safety and the efficacy of a nighttime melatonin intake on dynamic postural balance and lower-extremity muscle strength the following morning in PwMS. METHODS: Fourteen PwMS (28.36 ± 6.81 years) were assessed (8 a.m.) pre- and post-acute intake of melatonin or placebo (6mg, 30 minutes before nocturnal bedtime). Evaluated parameters included dynamic postural balance (force platform), lower-extremity muscle strength [Five-Repetition Sit-To-Stand Test (5-STST)], hand dexterity (Nine-Hole Peg Test), nociceptive pain [Visual Analogue Scale (VAS)], neuropathic pain [Neuropathic Pain 4 Questions (DN4)], sleep quality and fatigue perception [Hooper Index (HI)]. RESULTS: In the frontal plane, melatonin reduced the center of pressure (CoP) path length (CoPL), CoPL in the anteroposterior axis (CoPLY) and CoP sway area (CoPAr) compared with placebo by 7.56% (p=0.02, Cohens'd (d)=1.24), 19.27% (p<0.001, d=2.60) and 13.82% (p<0.001, d=2.02), respectively. Melatonin induced a higher decrease in these posturographic parameters compared with placebo in the sagittal plane [CoPL: 9.10% (p=0.005, d=1.02), CoPLY: 4.29% (p=0.025, d=1.07) and CoPAr: 7.45% (p=0.038, d=0.74)]. Melatonin decreased 5-STST duration as well as VAS, DN4, HI-fatigue and HI-sleep scores compared with placebo by 8.19% (p=0.008, d=1.19), 5.74% (p=0.04, d=0.82), 27.30% (p=0.023, d=0.98), 40.15% (p=0.044, d=0.85) and 30.16% (p=0.012, d=1.10), respectively. CONCLUSION: This preliminary study, among PwMS, showed that acute melatonin ingestion was safe and efficient for improving dynamic postural stability and lower-extremity muscle strength probably through its analgesic and anti-fatigue effects.

The effect of electromyography triggered electrical stimulation to abdominal muscles on sitting balance, respiratory functions, and abdominal muscle thickness in complete spinal cord injury: a randomized controlled trial.

Complete thoracic spinal cord injury (SCI) results in a loss of innervation to the abdominal muscles, which affects trunk stability and performance of activities of daily living from a sitting position. Respiratory function is also affected, leading to frequent pulmonary complications. Given the importance of trunk stability and respiratory function, we investigated the effects of electromyography triggered electrical stimulation (EMG-ES) applied to the abdominal muscles on sitting balance, respiratory functions and abdominal muscle thickness in individuals with complete thoracic SCI. This randomized controlled study included 34 participants with complete thoracic SCI who were randomly allocated to the experimental group ( n  = 17) and the control group ( n  = 17). During the 4-week intervention period, the experimental group received EMG-ES to their abdominal muscles, while the control group received isometric abdominal exercises three times per week. Both groups continued with their routine rehabilitation program (active or passive range of motion exercises, stretching, and balance coordination exercises). The primary outcome measures were the modified functional reach test (mFRT) and trunk control test (TCT). Secondary outcome measures included a pulmonary function test (PFT) and the bilateral abdominal muscle thicknesses using ultrasonography. At the end of the study, the experimental group showed significantly greater improvements in both primary outcomes. The mean difference in pre-post changes between the groups for the mFRT area was 242.8 cm² [95% confidence interval (CI): 181.3-329.8; effect size 0.92; P  < 0.001] and 5.0 points for TCT (95% CI: 3.9-6.0; effect size 0.98, P  < 0.001). The increase in the abdominal muscle thickness was also significantly greater in the experimental group ( P  < 0.001) without significant differences in the PFT ( P  > 0.05). We conclude that adding EMG-ES of abdominal muscles may further improve sitting balance and abdominal muscle thickness in individuals with complete thoracic SCI.

Individuals with knee osteoarthritis show few limitations in balance recovery responses after moderate gait perturbations.

BACKGROUND: Knee osteoarthritis causes structural joint damage. The resultant symptoms can impair the ability to recover from unexpected gait perturbations. This study compared balance recovery responses to moderate gait perturbations between individuals with knee osteoarthritis and healthy individuals. METHODS: Kinematic data of 35 individuals with end-stage knee osteoarthritis, and 32 healthy individuals in the same age range were obtained during perturbed walking on a treadmill at 1.0 m/s. Participants received anteroposterior (acceleration or deceleration) or mediolateral perturbations during the stance phase. Changes from baseline in margin of stability, step length, step time, and step width during the first two steps after perturbation were compared between groups using a linear regression model. Extrapolated center of mass excursion was descriptively analyzed. FINDINGS: After all perturbation modes, extrapolated center of mass trajectories overlapped between individuals with knee osteoarthritis and healthy individuals. Participants predominantly responded to mediolateral perturbations by adjusting their step width, and to anteroposterior perturbations by adjusting step length and step time. None of the perturbation modes yielded between-group differences in changes in margin of stability and step width during the first two steps after perturbation. Small between-group differences were observed for step length (i.e. 2 cm) of the second step after mediolateral and anteroposterior perturbations, and for step time (i.e. 0.01-0.02 s) of first step after mediolateral perturbations and the second step after outward and belt acceleration perturbations. INTERPRETATION: Despite considerable pain and damage to the knee joint, individuals with knee osteoarthritis showed comparable balance recovery responses after moderate gait perturbations to healthy participants.

Reorganization of structural brain networks in Parkinson's disease with postural instability/gait difficulty.

The Postural Instability/Gait Difficulty (PIGD) subtype of Parkinson's disease (PD) has a faster disease progression, a higher risk of cognitive and motor decline, yet the alterations of structural topological organization remain unknown. Diffusion Tensor Imaging (DTI) and 3D-TI scanning were conducted on 31 PD patients with PIGD (PD-PIGD), 30 PD patients without PIGD (PD-non-PIGD) and 35 Healthy Controls (HCs). Structural networks were constructed using DTI brain white matter fiber tractography. A graph theory approach was applied to characterize the topological properties of complex structural networks, and the relationships between significantly different network metrics and motor deficits were analyzed within the PD-PIGD group. PD-PIGD patients exhibited increased shortest path length compared with PD-non-PIGD and HCs (P < 0.05, respectively). Additionally, PD-PIGD patients exhibited decreased nodal properties, mainly in the cerebellar vermis, prefrontal cortex, paracentral lobule, and visual regions. Notably, the degree centrality of the cerebellar vermis was negatively correlated with the PIGD score (r = -0.390; P = 0.030) and Unified Parkinson's Disease Rating Scale Part III score (r = -0.436; P = 0.014) in PD-PIGD patients. Furthermore, network-based statistical analysis revealed decreased structural connectivity between the prefrontal lobe, putamen, supplementary motor area, insula, and cingulate gyrus in PD-PIGD patients. Our findings demonstrated that PD-PIGD patients existed abnormal structural connectomes in the cerebellar vermis, frontal-parietal cortex and visual regions. These topological differences can provide a topological perspective for understanding the potential pathophysiological mechanisms of PIGD in PD.

Effects of galvanic vestibular stimulation on postural righting reactions in hemiplegia.

Patients with post-stroke hemiplegia often exhibit reduced ability to maintain sitting balance, a crucial factor for predicting prognosis. Galvanic vestibular stimulation (GVS) influences postural control by stimulating vestibular organ. Although several studies have focused on GVS in static postures, no studies have demonstrated the influence of GVS on righting reactions. Therefore, we aimed to investigate the effects of GVS on postural righting reactions in seated patients with stroke-induced hemiplegia. Using a vertical board (VB), righting reactions were induced by tilting the VB at 10° after patients sat for 1 min. Patients adjusted their bodies until feeling vertical upon prompt. Twenty-two left hemiplegic patients with cerebrovascular disease participated, divided into two groups undergoing right cathode GVS (RC-GVS) followed by left cathode GVS or vice versa, preceded by sham stimulation. Centre of pressure and the joint angle were measured. During the postural righting reactions towards the paralysed side, RC-GVS enhanced the righting reactions and moved the mean position on the x-axis (COPx) to the right and the mean position on the y-axis (COPy) to the front. During the postural righting reaction towards the right side, RC-GVS induced resistance against the righting reaction, COPx was deflected to the right, COPy was deflected backward, and the angle of the neck tilt increased. The findings revealed that GVS with anodal stimulation on the paralysed side could promote righting reactions in patients with post-stroke hemiplegia. SIGNIFICANCE STATEMENT: The study findings suggest that using the contralesional placement of the anode promotes righting reactions, and galvanic vestibular stimulation can induce joint movements in the neck and trunk by polarising it to act as resistance against righting reactions.

Immediate effect of kinesiology taping on muscle strength, static balance and proprioception after eccentric muscle fatigue on ankle: a randomized cross-over trial.

BACKGROUND: Kinesiology Taping(KT) is commonly used as a physical therapy to prevent exercise-induced fatigue. This study aims to evaluate the immediate effects of KT on muscle strength, static balance, and proprioception after eccentric muscle fatigue on ankle. METHODS: Twenty healthy male university students were recruited. The experimental protocol was structured into four sessions, each separated by a one-week washout period to prevent carryover effects. Participants were randomly allocated to one of four intervention conditions in each session, ensuring no participant received the same intervention twice. These conditions were: no taping(NT),sham taping(ST),athletic taping(AT),and kinesiology taping(KT).Taping was applied immediately following an eccentric muscle fatigue protocol targeting the ankle, and assessments were conducted in the order of proprioception, muscle strength and static balance. Isometric muscle strength and proprioception were evaluated using the Biodex isokinetic system. Static balance was measured using the TecnoBody balance platform. RESULTS: KT had a significantly higher plantarflexion/dorsiflexion peak torque, dorsiflexion average peak torque, and plantarflexion/dorsiflexion average power at 60°/s compared with NT and ST in terms of isometric muscle strength (p < 0.05).Furthermore, the plantarflexion peak torque of KT was significantly greater than AT at 60°/s[p = 0.005,95% confidence interval(CI) = 3.39 to 18.20] and 180°/s[p = 0.006,95%CI(2.62,21.98)]. In terms of proprioception, KT showed a lower absolute error in 25° plantarflexion and 10° dorsiflexion compared to NT, ST and AT. For static balance with eyes-open and eyes-closed conditions, AT and KT had a lower total sway area than NT and ST (p < 0.05). Additionally, a significant difference in total sway length with eyes-open condition was observed between AT and KT[p < 0.001,95%CI(-431.81,-168.25)];total sway area and the center of pressure(COP) velocity in the mediolateral(ML) and anteroposterior(AP) directions with eyes-closed condition were significantly lower in AT compared to KT. CONCLUSION: This study suggests that KT is more effective than other taping conditions in improving muscle strength and proprioception after eccentric muscle fatigue on ankle. However, AT is more helpful in increasing static postural control ability after ankle muscle fatigue than KT. TRIAL REGISTRATION: This study was registered with www.chictr.org.cn (registration number: ChiCTR2300068278) on 13/2/2023.

Principal Component Analysis Enhanced with Bootstrapped Confidence Interval for the Classification of Parkinsonian Patients Using Gaussian Mixture Model and Gait Initiation Parameters.

Parkinson's disease is one of the major neurodegenerative diseases that affects the postural stability of patients, especially during gait initiation. There is actually an increasing demand for the development of new non-pharmacological tools that can easily classify healthy/affected patients as well as the degree of evolution of the disease. The experimental characterization of gait initiation (GI) is usually done through the simultaneous acquisition of about 20 variables, resulting in very large datasets. Dimension reduction tools are therefore suitable, considering the complexity of the physiological processes involved. The principal Component Analysis (PCA) is very powerful at reducing the dimensionality of large datasets and emphasizing correlations between variables. In this paper, the Principal Component Analysis (PCA) was enhanced with bootstrapping and applied to the study of the GI to identify the 3 majors sets of variables influencing the postural control disability of Parkinsonian patients during GI. We show that the combination of these methods can lead to a significant improvement in the unsupervised classification of healthy/affected patients using a Gaussian mixture model, since it leads to a reduced confidence interval on the estimated parameters. The benefits of this method for the identification and study of the efficiency of potential treatments is not addressed in this paper but could be addressed in future works.

Trunk-oriented Exercises Versus Whole-body Vibration on Abdominal Thickness and Balance in Children with Duchene Muscular Dystrophy.

OBJECTIVES: Progressive proximal muscle weakening in children with Duchenne muscular dystrophy (DMD) impairs postural adjustments by impairing motor function and preventing ambulation. During daily activities, for gait and dynamic balance, certain postural modifications are required. The objective was to compare the impact of trunk-oriented exercises versus whole-body vibration on abdominal muscle thickness and balance in children with DMD. METHODS: Participants in this study were 30 boys with DMD, aged 6 to 10 years old. Children were divided into two groups (A and B) randomly. Children in group (A) underwent a prescribed regimen of physical therapy along with trunk-oriented exercises, whereas group (B) received the same regimen as group (A) together with whole-body vibration three times per week for three consecutive months. Balance and the thickness of the abdominal muscles were measured using the Biodex balance system and ultrasonography, respectively, before and after therapy. RESULTS: When compared to the pre-treatment results in both groups, the post-treatment results showed a significant difference in all measured variables (p<0.05). Post-treatment values showed that all of the measured variables significantly differed in favor of group A. CONCLUSIONS: Trunk-oriented exercises can improve abdominal thickness and balance more effectively than whole-body vibration in children with DMD. CLINICALTRIALS: gov ID: NCT05688072.

Effects of Taekkyon-based exercise program on balance, lower extremity strength, and gait parameters in community-dwelling older women: Randomized controlled trial.

BACKGROUND: As individuals age, they experience a decline in muscle strength and balance, leading to diminished functional capacity and an increased risk of falls. The purpose of the current study was to investigate the effects of the Taekkyon-based exercise program on balance, muscle strength, and gait ability in women aged over 65-year-old residing in the local community. METHODS: Forty-eight subjects were randomly allocated into the Taekkyon-based exercise program as an experimental group (EG = 25; mean age: 71.68 ±â€…3.26) or a fall prevention program as a control group (CG = 23; mean age: 73.65 ±â€…5.88). EG participants received 1-hour Taekkyon exercise sessions twice a week for 12 consecutive weeks. CG participants received a typical fall prevention program. The measurements in each group included assessments of balance levels (the timed up-and-go test, one-leg stance, and functional reach test), lower extremity strength (the 5-chair stand test and 30-second chair stand test), and gait parameters (cadence, step length, step width, stride length, stride time, and gait velocity) before and after the intervention. RESULTS: After the intervention, balance (timed up-and-go test, one-leg stance, and functional reach test), lower extremity strength (5-chair stand test and 30-second chair stand test), and gait parameters (cadence, stride time, and gait velocity) showed a significant improvement in EG participants compared to CG participants (P < .05). Compared to the normal value of balance ability and strength of elderly women over 65 years of age, most outcomes were greater than average normal values for those receiving Taekkyon exercise. CONCLUSION: Taekkyon-based exercise program was more effective in improving balance, lower extremity strength, and gait capacity than the usual fall prevention program in elderly women over 65 years of age. Its effects can approach normal values for women in this age group. The 12-week Taekkyon-based exercise program could be useful as part of a fall prevention program to elderly people.

Altered foot placement modulation with somatosensory stimulation in people with chronic stroke.

Many individuals who experience a stroke exhibit reduced modulation of their mediolateral foot placement, an important gait stabilization strategy. One factor that may contribute to this deficit is altered somatosensory processing, which can be probed by applying vibration to the involved muscles (e.g., the hip abductors). The purpose of this study was to investigate whether appropriately controlled hip abductor vibration can increase foot placement modulation among people with chronic stroke. 40 people with chronic stroke performed a series of treadmill walking trials without vibration and with vibration of either the hip abductors or lateral trunk (a control condition) that scaled with their real-time mediolateral motion. To assess participants' vibration sensitivity, we also measured vibration detection threshold and lateral sway evoked by abductor vibration during quiet standing. As a group, foot placement modulation increased significantly with either hip or trunk vibration, compared to without vibration. However, these changes were quite variable across participants, and were not predicted by either vibration detection threshold or the lateral sway evoked by hip vibration during standing. Overall, we found that somatosensory stimulation had small, positive effects on post-stroke foot placement modulation. Unexpectedly, these effects were observed with both hip abductor and lateral trunk vibration, perhaps indicating that the trunk can also provide useful somatosensory feedback during walking. Future work is needed to determine whether repeated application of such somatosensory stimulation can produce sustained effects on this important gait stabilization strategy.

Improvement of postural control in the frail older adults through foot care: A pre- and post-intervention study.

Frailty in older adults often leads to foot issues, increasing fall-related fracture risk. Mechanoreceptors, the pressure receptors in the foot sole, are pivotal for postural control. Foot problems can impair mechanoreceptor function, compromising balance. This study aimed to examine the effect of foot care on postural control in frail older adults. Forty-eight participants underwent a five-month monthly foot care intervention. Measurements were taken before and after this intervention. Participants stood for 45 s in a static, open-eyed position on a stabilometer. Center-of-pressure (CoP) analysis included total trajectory length, integrated triangle area, rectangular area, and range of motion in anterior-posterior and medio-lateral directions. Results indicated that foot care significantly increased toe ground contact area by 1.3 times and improved anterior-posterior motion control during static standing. Enhanced postural control resulted from improved skin condition due to foot care that intensified mechanoreceptor signal input and improved postural control output. These findings underscore the potential for reducing fracture risks in older adults through proactive foot care. The study highlights the vital role of foot care in enhancing postural control, with broader implications for aging population well-being and safety.

Effects of Cognitive Inhibition Preceding Voluntary Step Responses to Visual Stimuli in Young and Older Adults.

OBJECTIVES: Age-related changes in executive functions, especially inhibitory control, correlate to decreased balance control and increased fall risk. However, only a few studies focused on the performance of tasks integrating balance and inhibitory control. This study aims to determine the effects of cognitive inhibition preceding the initiation of voluntary steps in young and older adults. METHODS: Performance of 3 stepping tasks (a Simon, Flanker, and a combined Simon-Flanker task [SFT]) were analyzed in 23 young adults and 43 older adults. Each task included congruent and incongruent trials in different step directions. Analyses focused on temporal aspects of step responses as identified by changes in Center of Pressure (CoP) and foot position. A 3-way repeated-measures ANOVA was used to evaluate "inhibition," "age," and "task" effects. RESULTS: With large effect sizes, "inhibition" as well as "age" resulted in longer durations of an initial preparatory phase as well as the step response phase. The SFT showed the largest "task" effects. Duration of CoP movement had the largest impact on total step execution in older adults. A significant interaction effect of "age*inhibition" was found on the duration of CoP movement, but not on CoP onset. DISCUSSION: Overall, our results demonstrate that cognitive inhibition has more impact in older adults, the longer duration of CoP movements in older adults may reflect an ineffective step preparation. Our examination of the duration of subsequent phases which comprise perceptual processing and conflict resolution, response initiation, and step execution sheds light on how cognitive inhibition affects voluntary stepping behavior in young and older adults.

The influence of fear of falling on the control of upright stance across the lifespan.

BACKGROUND: Standing at height, and subsequent changes in emotional state (e.g., fear of falling), lead to robust alterations in balance in adults. However, little is known about how height-induced postural threat affects balance performance in children. Children may lack the cognitive capability necessary to inhibit the processing of threat and fear-related stimuli, and as a result, may show more marked (and perhaps detrimental) changes in postural control compared to adults. This work explored the emotional and balance responses to standing at height in children, and compared responses to young and older adults. METHODS: Children (age: 9.7 ± 0.8 years, n = 38), young adults (age: 21.8 ± 4.0 years, n = 45) and older adults (age: 73.3 ± 5.0 years, n = 15) stood in bipedal stance in two conditions: at ground level and 80 cm above ground. Centre of pressure (COP) amplitude (RMS), frequency (MPF) and complexity (sample entropy) were calculated to infer postural performance and strategy. Emotional responses were quantified by assessing balance confidence, fear of falling and perceived instability. RESULTS: Young and older adults demonstrated a postural adaptation characterised by increased frequency and decreased amplitude of the COP, in conjunction with increased COP complexity (sample entropy). In contrast, children demonstrated opposite patterns of changes: they exhibited an increase in COP amplitude and decrease in both frequency and complexity when standing at height. SIGNIFICANCE: Children and adults adopted different postural control strategies when standing at height. Whilst young and older adults exhibited a potentially protective "stiffening" response to a height-induced threat, children demonstrated a potentially maladaptive and ineffective postural adaptation strategy. These observations expand upon existing postural threat related research in adults, providing important new insight into understanding how children respond to standing in a hazardous situation.

People with degenerative cervical myelopathy have impaired reactive balance during walking.

BACKGROUND: People with degenerative cervical myelopathy are known to have impaired standing balance and walking abilities, but less is known about balance responses during walking. RESEARCH QUESTION: The aim of this project was to assess reactive balance impairments during walking in people with degenerative cervical myelopathy (PwDCM). We hypothesized that center of mass motion following perturbations would be larger in PwDCM and gluteus medius electromyographic amplitude responses would be decreased in PwDCM. METHODS: Reactive balance responses were quantified during unanticipated lateral pulls to the waist while treadmill walking. Walking biomechanics data were collected from 10 PwDCM (F=6) and 10 non-myelopathic controls (F=7) using an 8 camera Vicon System (Vicon MX T-Series). Electromyography was collected from lower limb muscles. Participants walked on an instrumented treadmill and received lateral pulls at random intervals and in randomized direction at 5% and 2.5% body mass. Participants walked at 3 prescribed foot placements to control for effects of the size of base of support. RESULTS: As compared with controls, the perturbation-related positional change of the center of mass motion (ΔCOM) was increased in PwDCM (p=0.001) with similar changes in foot placement (p>0.05). Change in gluteus medius electromyography, however, was less in PwDCM than in controls (p<0.001). SIGNIFICANCE: After experimentally controlling step width, people with mild-to-moderate degenerative cervical myelopathy at least 3 months following cervical spine surgery have impaired reactive balance during walking likely coupled with reduced gluteus medius electromyographic responses. Rehabilitation programs focusing on reactive balance and power are likely necessary for this population.