Changes In Postural Stability Research Articles

Changes in postural stability after cerebrospinal fluid tap test in patients with idiopathic normal pressure hydrocephalus.

In patients with idiopathic normal pressure hydrocephalus (iNPH), the characteristics of balance disturbance are not as well understood as those related to gait. This study examined changes in postural stability in quiet standing after the cerebrospinal fluid tap test (CSFTT) in these patients. Furthermore, the study explored the relationship between the amount of spontaneous body sway and both gait and executive function. All patients diagnosed with iNPH underwent CSFTT. We evaluated their center of pressure (COP) measurements on a force plate during quiet standing, both pre- and post-CSFTT. Following the COP measurements, we calculated COP parameters using time and frequency domain analysis and assessed changes in these parameters after CSFTT. At pre-CSFTT, we assessed the Timed Up and Go (TUG) and the Frontal Assessment Battery (FAB). We investigated the relationship between COP parameters and the TUG and FAB scores at pre-CSFTT. A total of 72 patients with iNPH were initially enrolled, and 56 patients who responded positively to CSFTT were finally included. Post-CSFTT, significant improvements were observed in COP parameters through time domain analysis. These included the velocity of COP (vCOP), root-mean-square of COP (rmsCOP), turn index, torque, and base of support (BOS), compared to the pre-CSFTT values (p < 0.05). In the frequency domain analysis of COP parameters post-CSFTT, there was a decrease in both the peak and average of power spectral density (PSD) values in both the anteroposterior (AP) and mediolateral (ML) directions below 0.5 Hz (p < 0.05). In addition, the TUG scores showed a positive correlation with vCOP, rmsCOP, turn index, torque, BOS, and both the peak and average PSD values in the AP and ML directions below 0.5 Hz (p < 0.05). The FAB scores demonstrated a negative correlation with vCOP, rmsCOP, turns index, BOS, and both peak and average PSD values in the AP direction below 0.5 Hz (p < 0.05). In patients with iNPH who responded to CSFTT, there was an improvement in spontaneous body sway during quiet standing after CSFTT. Increased spontaneous sway is associated with impaired gait and frontal lobe function. This may be linked to impaired cortico-cortical and cortico-subcortical circuits in patients with iNPH.

Intersession reliability of center of pressure measurement during bipedal standing with different foot placement angles

IntroductionThe foot placement is a determinant of the base of support and influences standing balance. The reliability of postural stability tests with different foot placement angles is unclear. Research questionTo determine and compare the intra- and inter-day reliability of the center of pressure-based postural stability while standing with different foot placement angles. MethodTwenty-five healthy adults (16 females and 9 males; age: 29 ± 6 years) completed 70 s trials of eyes open and eyes closed stability tests with 0°, 15°, 30°, and 45° angles between the feet while standing on a forceplate in three sessions: two sessions were in the same day, and the third session was one-week apart. The repeatability of measurements was tested using analysis of variance, interclass correlation, and standard error of measurements. ResultThroughout the three study sessions, there was no difference in postural stability while participants stood with different foot placement angles. The interclass correlation scores ranged from 0.71 to 0.96, the standard error of measurements ranged from 2.1% to 12.9%, and no significant systematic changes (p < 0.05) occurred between the testing sessions for any foot placements. Standing with a 45° angle between the feet with closed eyes showed higher reliability values than other conditions. The intra-day reliability scores were greater than inter-day reliability. DiscussionThe relative reliability of postural stability could be impacted by foot placement angles, which might alter ankle mobility and base of support dimensions. The advantages of larger foot placement angles on improving the relative reliability of postural stability could be better demonstrated in healthy people under challenging conditions such as standing with closed eyes. ConclusionStanding with foot placement angles between 0° and 45° are reliable and a quantitative assessment of the center of pressure could be used to monitor the changes in postural stability between sessions.

외사위의 프리즘 교정에 따른 자세 안정성의 변화

외사위의 프리즘 교정에 따른 자세 안정성의 변화

Effects of Foot Structure Type on Core Stability in University Athletes.

This study assessed the impact of different types of medial foot arch on postural stability and core center of gravity muscle activity among collegiate athletes. The study sample included 103 university-level athletes across various sports (soccer, rugby, basketball, volleyball, field tennis, table tennis, karate, and cheerleading) from the College of Magdalena (Colombia) who exhibited distinct types of medial foot arch: 32 high, 35 low, and 36 neutral arches. Surface electromyography (sEMG) was employed to assess conduction velocity, magnitude values, latency, and fatigue in focal muscles including the spinal erector (SE), internal oblique (IO), external oblique (EO), and rectus abdominis (AR), while measurements of static and dynamic postural control were also considered. Post hoc analysis was performed with Bonferroni correction for all electromyographically measured muscle groups, as well as for measurements of static and dynamic postural stability. Pearson's or Spearman's correlation tests were used to compare the different types of feet. There were no substantial differences observed between the distinct types of feet in terms of focal muscle activity, static stability, or dynamics. Even though the mean values indicated higher muscle activity and stability among those with high foot arches and lower values among those with low arches compared to the neutral foot type, this observed difference was deemed statistically insignificant. We also observed a positive correlation between internal oblique muscle activity and the average power of dynamic postural stability, which remained consistent across all foot types. Our findings indicate that static instability is directly correlated with dynamic instability in the anteroposterior direction, while a clear inverse relationship was established in the lateral direction upon examining the variable correlations. The presence of high or low foot arches did not significantly impact the activity of the muscles responsible for maintaining the body's center of gravity or postural stability among university-level athletes. This suggests the existence of neuromuscular compensation mechanisms that attempt to restore balance and compensate for any changes in postural stability caused by varying foot types. Through targeted training that emphasizes activation of the internal oblique muscle, athletes may see improved postural stability. Our findings indicate that static stabilization exercises can also prove beneficial in improving dynamic stability in the anteroposterior plane, while a more dynamic approach may be required to improve dynamic stability in the lateral plane.

Postural Stability Changes Following Static Loading in Athletes with and without Anterior Cruciate Ligament Reconstruction

Introduction: This study investigated the effect of change in postural stability after applying static load during internal perturbation among professional athletes with and without anterior cruciate ligament (ACL) surgery.&#x0D; Materials and Methods: The participants of the present study were 20 athletes with sixteen months post ACL reconstruction surgery and 20 healthy matched athletes. Each participant performed transitional tasks from double limb stance to single leg stance (SLS) and again to double limb stance on the force plate before and after the application of 10 minutes of constant loading. Area, fore-after range (the meaning of fore-after is anterior- posterior and in articles, this term has been used instead of anterior-posterior) range fore- after (Rfa), range sideway (Rsw), mean velocity (Mv) and confidence ellipse (Ce) of the center of pressure were measured.&#x0D; Results: Rsw (P=0.009) and area (P=0.009) in response to static loading in the healthy group showed a decrease and an increase of area (P=0.009) in response to static loading in the ACLR group was seen on the double limb stance phase. Mv (P&lt;0.001) and area (P&lt;0.001) were bigger in the ACLR group after static loaded on the integration phase.&#x0D; Conclusion: Decreased capacity of passive structures to maintain postural stability against perturbation was observed due to positional change among athletes with a history of ACL reconstruction surgery.

Effects of Different Forms of Sensorimotor Training on Postural Control and Functional Status in Patients with Chronic Low Back Pain.

The aim of this study was to compare three sensorimotor training forms in patients with chronic low back pain to determine their effects on the reduction of pain-related impairment and changes in posturography. Over two weeks, during the multimodal pain therapy (MMPT) period, six sessions of sensorimotor physiotherapy or training in the Galileo® or Posturomed® (n = 25 per group) were performed. A significant reduction in pain-related impairment after the intervention phase was shown across all groups (time effect: p < 0.001; ηp2 = 0.415). There was no change in postural stability (time effect: p = 0.666; ηp2 = 0.003), but there was a significant improvement in the peripheral vestibular system (time effect: p = 0.014; ηp2 = 0.081). An interaction effect was calculated for the forefoot-hindfoot ratio (p = 0.014; ηp2 = 0.111). Only the Posturomed® group showed an improvement in anterior-posterior weight distribution (heel load: 47% vs. 49%). These findings suggest that these forms of sensorimotor training in the context of MMPT are suitable for reducing pain-related impairment. Posturography demonstrated stimulation of a subsystem, but no improvement in postural stability.

123 Early Postural Stability Changes in Patients Undergoing Correction of Spinal Deformity

INTRODUCTION: Adult spinal deformity (ASD) is an increasingly prevalent cause of pain and disability. It is known that ASD correction results in improved alignment, but not whether this alignment results in objective improvements in postural stability. METHODS: A retrospective review of a prospectively maintained database identified 16 patients undergoing ASD correction surgery with five or more segments. Balance was assessed via a force plate pre- and three months postoperatively. Participants were instructed to stand still, with their hands at their sides and eyes open. Center of pressure (COP) and center of gravity (COG) parameters were analyzed and used to derive head sway in the Dubousset cone of economy (COE). Spinopelvic parameters (PI, PT, SVA, and LL) on standing scoliosis radiographic films were also measured pre- and three months postoperatively. RESULTS: In our 16-patient series, there was a mean age of 61.3 years-old, and a median of 10 segments fused. Postoperative force plate assessment showed a decrease in total COP sway and sway velocity (p &lt; 0.05). Coronal COP sway and sway velocity also decreased (p &lt; 0.05). There was a decrease in total, coronal and sagittal COG sway and sway velocity postoperatively (p &lt; 0.05). In the COE, total head sway decreased (p &lt; 0.05). PT remained unchanged following surgical correction, while LL and SVA improved from 44.9° to 56.7° (p &lt; 0.01) and 82.2 to 22.5 mm (p &lt; 0.01), respectively. PI-LL mismatch also improved from 16.2° to 4.8° (p &lt; 0.01). CONCLUSIONS: Following long segment fusion for ASD, postural stability may improve as early as three months, concomitant with improved spinopelvic alignment. We believe force plate assessment warrants further study for postoperative evaluation of postural alignment and clinical outcomes in ASD patients.

At-home assessment of postural stability in parkinson’s disease: a vision-based approach

Postural instability is one of the most disabling symptoms of Parkinson’s Disease, with important impacts on people safety and quality of life since it increases the risk of falls and injuries. Home monitoring of changes in postural stability, as a consequence of therapies and disease progression, is highly desirable for the safety of the patient and better disease management. In this context, we present a system for the automatic evaluation of postural stability that is suitable for self-managing by people with motor impairment directly at home. The system is based on an optical RGB-Depth device, which tracks the body movements both for system’s interaction, thanks to a gesture-based human-machine interface, and the automated assessment of postural stability. A set of tasks, based on standard clinical scales, has been designed for the assessment. The user controls the delivery of the tasks through the system interface. A machine learning approach is adopted, and some kinematic parameters that characterize the user’s performance during each task execution are estimated and used by supervised classifiers for the automatic assessment. Data collected during experimental clinical trials were used to train the classifiers. This approach supports the compliance of the classifier assessments with respect to the clinical ones. The system prototype and the preliminary results on its accuracy in the assessment of postural stability are presented and discussed.

Effects of Posterior Spinal Correction and Fusion on Postural Stability in Patients with Adolescent Idiopathic Scoliosis

The present study aimed to assess the effects of posterior spinal correction and fusion on postural stability in patients with adolescent idiopathic scoliosis (AIS). The study included 41 female patients with AIS at our institution. All patients performed three 10 s single-leg standing trials on a force plate. The center of pressure (COP) was measured preoperatively, and at 1 week and 6 months postoperatively. The postural stability parameters were absolute minimum time-to-boundary (TTB), mean of the minimum TTB, mean COP velocity, standard deviation, range, and 95% confidence ellipse area. One-way repeated analysis of variance or Friedman test was applied to the postural stability parameters. Multiple comparisons were performed using the Bonferroni correction. The absolute minimum TTB and the mean minimum TTB showed a significant increase 6 months post-operation as compared to preoperatively and 1 week postoperatively. The COP velocity significantly decreased at 6 months post-operation compared to preoperatively and 1 week postoperatively. These changes in postural stability indicate that spinal correction and fusion can be considered to improve postural stability during single-leg standing tests in the postoperative period.

Dynamic Postural Stability Among Individuals With Parkinson's Disease Following Performance-Based Overground Locomotor Training

Individuals with Parkinson’s disease (PD) exhibit compromised dynamic postural stability with impaired gait and balance, which contribute to walking limitations. Performing turns while walking perturbs mediolateral stability, challenges the daily functioning of people with PD, and is attributed to altered thoracic movement patterns that include reducing peak turn velocity (°/s). Although previous studies in our lab demonstrated that individuals with neurological impairments improved walking capacity following performance-based overground locomotor training (OLT), dynamic postural stability changes following OLT in people with PD remain unknown. PURPOSE: Characterize changes in dynamic postural stability during turns while walking among individuals with PD following OLT, evidenced by peak turn velocity change. METHODS: Twelve participants with PD (7 Male / 5 Female; Age: 68.5 ± 6.4 years; Hoehn and Yahr: 1-3) completed 24 60-minute OLT sessions twice-weekly. Baseline (PRE) and follow-up (POST) assessments included the 10-minute walk test (10MWT) indoors along a 60-meter corridor while wearing inertial sensors around the fourth lumbar vertebra and the sternum. Angular velocity was collected from each sensor and processed offline. First, turns were identified using integrated lumbar data and extracted from the sternum sensor. Next, peak turn velocity was averaged across all turns at PRE and POST, respectively. Finally, the mean peak turn velocity changes were calculated in the frontal (PTVF) and transverse (PTVT) planes of motion. Positive (+) change reflects improved dynamic postural stability during turns. Statistical analysis included one-tailed t-tests and Cohen’s d effect size. RESULTS: Completed turns increased after OLT (+1.5 ± 1.51; p < 0.01). PTVF showed a moderate and significant increase following OLT (+1.59 ± 2.18 °/s; 95%CI: 0.20, 2.98; p = 0.014; Cohen’s d = 0.43) while PTVT change was small and not significant (+0.88 ± 3.18 °/s; 95%CI: -2.90, 1.14; p = 0.179; Cohen’s d = 0.25). CONCLUSION: This study provides preliminary evidence suggesting that participants moderately improved frontal plane dynamic postural stability during turns after OLT by adapting thoracic movement patterns in ways that likely attenuated perturbed mediolateral stability.

Effects of Diabetic Neuropathy on the Postural Stability of Adults with Type 2 Diabetes Mellitus

Diabetic peripheral neuropathy (DPN) is one of the most common complications, which occurs in 50–70% of people with Type 2 diabetes mellitus (T2DM). The disease usually affects the peripheral nerves and can cause loss of sensation in the feet, leading to impaired body equilibrium during quiet stance and gait, and elevated risk of falls. A total of 38 non-insulin-dependent T2DM adults (mean age 53.21 ± 7.74 years) – 18 with DPN and 20 without DPN, and 20 age- and sex-matched controls took part in the study. The DPN group was selected with standard clinical criteria and a Bulgarian version of the Michigan neuropathy screening instrument. Postural stability was evaluated with static posturography under two visual conditions (eyes open and eyes closed) on firm and soft support. Both diabetic groups exhibited significantly higher postural instability compared with the healthy controls, as well as stronger visual dependence. While standing on firm support, subjects with DPN exhibited significantly higher postural instability than those without DPN in the closed eyes condition only, whereas when standing on soft support, their postural stability was significantly more impaired compared with the diabetic subjects without DPN in both experimental conditions (open and closed eyes). A better understanding of the changes in postural stability in persons with T2DM would contribute to early diagnostics, rehabilitation and prevention of DPN.

In Patients with Grade I and II Ankle Sprains, Dynamic Taping Seems to Be Helpful during Certain Tasks, Exercises and Tests in Selected Phases of the Rehabilitation Process: A Preliminary Report.

We aimed to investigate changes in postural stability on a stable surface after the application of dynamic tape for patients with inversion ankle sprains. This study enrolled 30 patients (age 25.5 ± 8.0 years) with grade I and II ankle sprains, which occurred 7–21 days before enrolment. Postural stability (balance, coordination, feedback) was assessed before and after the application of dynamic tape using a stabilographic platform. Three 32-s exercises were performed on the stabilographic platform, one with eyes open, one with eyes closed and one with visual feedback. After the application of dynamic tape, an improvement was observed in terms of the mean radius of sway (4.2 ± 1.3 mm vs. 3.4 ± 0.9 mm; p = 0.012) and coordination (48.8 ± 19.2% vs. 59.3 ± 5.8%; p = 0.021). Selected balance parameters did not improve significantly in the tests with open and closed eyes. Asymmetric load improved for all tests, but significant differences were only observed with eyes closed (34.9 ± 24.4 vs. 41.7 ± 30.5; p < 0.01). We concluded that the use of dynamic tape after an ankle sprain significantly improved balance and coordination on a stable surface. The benefits were shown in terms of a significant improvement in the asymmetric load of the injured limb in comparison to the healthy limb during the test with closed eyes and a considerable improvement in the asymmetric load that was evaluated with visual feedback on a stable surface.

Bariatric surgery and exercise: A pilot study on postural stability in obese individuals.

This study aimed to analyze the changes in postural stability of individuals with obesity after bariatric surgery, and the effect of three months of regular exercise on the static postural stability. Twenty-two subjects (7 females and 15 males) aged 31 to 68 years (Body mass index 35–55 kg.m-2) completed the study. Participants were divided into two groups: one group participated in an exercise program after the bariatric surgery (n = 10; age 48.9 ± 7.5 years; Body mass index 42 ± 5.6 kg.m-2) while the second group did not exercise at all after bariatric surgery (n = 12; age 44.7 ± 13.6 years, Body mass index 42.6 ± 6.0 kg.m-2). Static postural stability was measured using a Tekscan MobileMat pressure plate before and 4 months after the bariatric surgery. The exercise program included exercising three times a week including: one hour of strengthening, one hour of aerobic group exercise and at least one session of individual exercise at home. There were no significant differences in Center of force sway, Center of force ranges and average speed before and 4 months after bariatric surgery. Also, no effect of exercise was found. Post-pre differences of some parameters were negatively related to age (r from—0.46 to—0.72). Further studies are needed to explore this topic in depth.

Neuroticism and Extraversion Are Related to Changes in Postural Stability During Anatomically-Related Cognitive Tasks

The relationship between personality and postural stability has received little attention. This study addressed whether neuroticism and extraversion correlate with changes in postural stability while performing cognitive tasks related to brain regions selectively associated with neuroticism and extraversion. Thirty-two adults stood on a foam mat in tandem stance and completed a 2-back task and a weather prediction task (WPT). As predicted, higher neuroticism was related to increased dual task sway during the 2-back task, r = 0.40, p = 0.023, and lower extraversion was related to increased dual task sway during the WPT, r = –0.43, p = 0.013, suggesting that personality is related to postural stability in healthy young adults and that personality could be considered in the prediction and treatment of individuals with balance difficulties.

The Influence of Pronated Foot Posture on Knee Isokinetic Strength, Static and Dynamic Postural Stability in Healthy Young Individuals

Background: The foot is a complex body structure that plays an important role in static and dynamic situations. Previous studies have reported that altered foot posture might affect knee joint strength and postural stability, however their relationship still remains unclear. Objects: The purpose of this study was to identify whether pronated foot posture has an influence on knee isokinetic strength and static and dynamic postural stability. Methods: Forty healthy young males aged 18 to 26 years were included. Foot posture was evaluated using the Foot Posture Index-6 (FPI-6), and the subjects were divided into two groups according to their FPI-6 scores: a neutral foot group (n = 20, FPI-6 score 0 to +5) and a pronated foot group (n = 20, FPI-6 score +6 or more). Biodex Systems 3 isokinetic dynamometer was used to evaluate knee isokinetic strength and hamstring to quadriceps ratio at three angular velocities: 60°/sec, 90°/sec, and 180°/sec. The static and dynamic postural stability in a single-leg stance under the eyes-open and eyes-closed conditions were measured with a Biodex Balance System. Results: There were no significant differences between the groups in knee isokinetic strength and static postural stability (p > 0.05), but there was a significant difference in the medial– lateral stability index (MLSI) for dynamic postural stability under the eyes-closed condition (p = 0.022). The FPI-6 scores correlated significantly only with the dynamic overall stability index (OSI) and the MLSI (OSI: R = 0.344, p = 0.030; MLSI: R = 0.409, p = 0.009) under the eyesclosed condition. Conclusion: Participants with pronated foot had poorer medial–lateral dynamic stability under an eyes-closed condition than those without, and FPI-6 scores were moderately positively correlated with dynamic OSI and dynamic MLSI under the eyes-closed condition. These results suggest that pronated foot posture could induce a change in postural stability, but not in knee isokinetic strength.

Postural stability changes after contrast immersion in ankle sprain (Randomized Controlled Trial)

Background: cryotherapy application is commonly used as a physical therapy tools with many advantages. Although often used, its impact on the postural balance is not well-known. Objectives: To investigate the effectiveness of contrast water immersion therapy on ankle posture stability in patients with lateral ankle sprain Methods: Thirty patients, grade I and II lateral ankle sprain their age ranged between 18 to 35 years they were randomly divided into two equal groups using coin flip. Interventions. Group (A) received selected physical therapy program for ankle sprain patients. Group (B) Received contrast water immersion for 16 min in addition to the same selected physical therapy program received by group (A) for 4 weeks. For both groups Biodex balance system was used to measure static and dynamic balance before and after treatment period. Results: analysis of data using ANOVA test, show that there was significant decrease in Overall stability index , Mediolateral stability index and Anteroposterior stability index of the study group compared with that of the control group post-treatment Conclusion: It’s concluded that contrast water immersion for fifteen minutes in patients with lateral ankle sprain had significant effect on static balance. Keywords: Static balance, contrast water immersion, ankle sprain.

Differences in the Effect of Sleep Deprivation on the Postural Stability among Men and Women

Objective: Sleepiness caused by sleep deprivation may increase the risk of injuries and damages during physical activity. Individual data so far indicate a generally better static postural stability of women regardless of sleeping conditions. The main aim of this study was to assess the impact of sleep deprivation on postural stability according to gender after 24 h of sleep deprivation. Methods: Participants included 83 students (36 men and 47 women). Postural stability was measured with eyes open and closed eyes before and after sleep deprivation. Data from posturographic platform were used to assess postural stability objectively. Results: The type of test determined the size of observed changes in postural stability. The data suggest that women are better able to cope with the effects of sleep deprivation than men. Conclusion: Postural control system is very important in sport and in physically active people. The results show that men are more sensitive to sleep deprivation than women because they had higher COP (center of pressure) values in tests. Less postural stability of the body due to sleep deprivation indicates a higher risk of injury during physical activity.

Changes in postural stability on balance platform in patients after meniscal repair – two years follow up

Purpose: The aim of this work was to evaluate postural stability on the balance platform averagely 2 years following meniscal repair. Methods: This is a retrospective, case-control comparative analysis of patients who underwent surgical repair for the isolated longitudinal traumatic meniscal tear versus matched healthy controls. The study group consisted of 30 patients (mean age 29.93 years; averagely 2.3 years after surgery) and the control group – of 30 people. Following physical examination and completion of the IKDC, and the Lysholm questionnaires, the evaluation of the postural stability using two single-leg stabilometry tests was performed. In the static test, the analyzed variables included deviations from the horizontal, vertical axes and the length of the balance path travelled. In the dynamic test, the length of the path travelled and the time to complete task were recorded. Between-limb and between-groups comparison of collected stabilometry tests were performed. Additionally, the IKDC and the Lysholm questionnaires scores were compared between the study and heathy groups. Results: No abnormalities were found on clinical examination in the study group nor any differences between the operated and contralateral knee (p &gt; 0.05). In stabilometry: (1) in the study group, the operated extremity scored worse than the contralateral limb (length of path traveled in: A) static test x = 56.7 cm SD = 37.91 cm vs. x = 21.6 cm SD = 9.06 cm; p = 0.002 and B) dynamic test x = 82.57 cm, SD = 50.43 cm vs. x = 53.32 cm, SD = 13.82 cm; p = 0.003); (2) In the control group, no leg-related differences were noted (p &gt; 0.05); (3) Between-group comparison revealed that the study group scored worse than the control group (length of path traveled in: A) static test x = 56.7 cm, SD = 37.91 cm vs. x = 17.23 cm, SD = 3.39 cm; p = 0.001 and B) dynamic test x = 82.57 cm, SD = 50.43 cm vs. x = 32.13 cm, SD = 9.41 cm; p &lt; 0.001). Study group scored worse on IKDC scores (p &lt; 0.001) but not on Lysholm score (p &gt; 0.05). Conclusions: Postural stability deficit persists despite a successful meniscal repair.

Classification of Rhythmic Cortical Activity Elicited by Whole-Body Balance Perturbations Suggests the Cortical Representation of Direction-Specific Changes in Postural Stability.

Postural responses that effectively recover balance following unexpected postural changes need to be tailored to the characteristics of the postural change. We hypothesized that cortical dynamics involved in top-down regulation of postural responses carry information about directional postural changes (i.e., sway) imposed by sudden perturbations to standing balance (i.e., support surface translations). To test our hypothesis, we evaluated the single-trial classification of perturbation-induced directional changes in postural stability from high-density EEG. We analyzed EEG recordings from six young able-bodied individuals and three older individuals with chronic hemiparetic stroke, which were acquired while individuals reacted to low-intensity balance perturbations. Using common spatial patterns for feature extraction and linear discriminant analysis or support vector machines for classification, we achieved classification accuracies above random level (p < 0.05; cross-validated) for the classification of four different sway directions (one vs. the rest scheme). Screening of spectral features (3-50 Hz) revealed that the highest classification performance occurred when low-frequency (3-10 Hz) spectral features were used. Strikingly, the participant-specific classification results were qualitatively similar between young able-bodied individuals and older individuals with chronic hemiparetic stroke. Our findings demonstrate that low-frequency spectral components, corresponding to the cortical theta rhythm, carry direction-specific information about changes in postural stability. Our work presents a new perspective on the cortical representation of postural stability and the possible role of the theta rhythm in the modulation of (directional) reactive balance responses. Importantly, our work provides preliminary evidence that the cortical encoding of direction-specific changes in postural stability is present in chronic hemiparetic stroke.

Cognitive Loading Produces Similar Change in Postural Stability in Patients With Chronic Ankle Instability and Controls.

While postural stability is compromised in individuals with chronic ankle instability (CAI), few studies have attempted to examine how performing simultaneous cognitive and balancing tasks may alter the complexity of the center of pressure. The purpose of this study was to compare postural stability in patients with CAI to controls during a dual-task condition via sample entropy. Thirty participants (15 CAI, 15 healthy control) performed 3-trials of single-leg stance for 60-seconds each under two different conditions: single-task and dual-task (serial subtraction). Sample entropy (SampEn), a measure of pattern regularity, was calculated from the center of pressure excursion in the anterio-posterior (AP) and medio-lateral (ML) directions. 2x2 mixed-model ANOVAs determined any differences by task or group (p≤0.05). SampEn-AP decreased in the dual-task condition compared to single-task, single-leg balance across groups (F1,28=8.23, p=0.008, d=0.53). A significant interaction for group by task was found for SampEn-ML (F1,28=4.18, p=0.05), but post hoc testing failed to reveal significant differences. Serial subtraction was completed with significantly fewer errors during dual-task compared to single-task (F1,27=12.75, p=0.001, d=0.66). Patients with CAI do not display differences in regularity of postural stability, even when attention is divided. However, the addition of serial subtraction increased the regularity of AP center-of-pressure motion. Increased regularity may suggest a change in motor control strategy, reducing natural fluctuations and flexibility within movement patterns during more challenging tasks. Clinicians could utilize dual-task situations during rehabilitation of patients with CAI, in order to adequately restore stability and function when attention is divided.