Sway Measures Research Articles

Quantifying States and Transitions of Emerging Postural Control for Children Not Yet Able to Sit Independently

Objective, quantitative postural data is limited for individuals who are non-ambulatory, especially for those who have not yet developed trunk control for sitting. There are no gold standard measurements to monitor the emergence of upright trunk control. Quantification of intermediate levels of postural control is critically needed to improve research and intervention for these individuals. Accelerometers and video were used to record postural alignment and stability for eight children with severe cerebral palsy aged 2 to 13 years, under two conditions, seated on a bench with only pelvic support and with additional thoracic support. This study developed an algorithm to classify vertical alignment and states of upright control; Stable, Wobble, Collapse, Rise and Fall from accelerometer data. Next, a Markov chain model was created to calculate a normative score for postural state and transition for each participant with each level of support. This tool allowed quantification of behaviors previously not captured in adult-based postural sway measures. Histogram and video recordings were used to confirm the output of the algorithm. Together, this tool revealed that providing external support allowed all participants: (1) to increase their time spent in the Stable state, and (2) to reduce the frequency of transitions between states. Furthermore, all participants except one showed improved state and transition scores when given external support.

Balancing new technology: Virtual reality for balance measurement case report.

Falling and the inability to maintain balance are the second leading cause of unintentional injury deaths globally. There are a number of chronic and acute conditions characterized by balance difficulties, including neurological diseases, and sport injuries. Therefore, methods to monitor and quantify balance are critical for clinical decision-making regarding risk management and balance rehabilitation. New advances in virtual reality (VR) technology has identified VR as a novel therapeutic platform. VRSway is a VR application that uses sensors attached to a virtual reality headset, and handheld remote controllers for measurement and analysis of postural stability by measuring changes in spatial location relative to the center of mass and calculates various postural stability indexes. This case report evaluates balance measures in 2 healthy participants with no previous history of balance disorders using the VRSway software application and compares to output generated by the current gold standard of balance measurement, force platform technology. The primary objective of this case study was to validate the VRSway stability score for evaluation of balance. Here, we present posturography measures of the VRSway in comparison with force plate readouts in 2 healthy participants. Body Sway measurements were recorded simultaneously in both the force plate and VRSway systems. Data calculated by proprietary software is highly correlative to the data generated by force plates for each of the following measurements for participant-1 and participant-2, respectively: Sway index (r1 = 0.985, P < .001; r2 = 0.970, P < .001), total displacement (r1 = 0.982, P < .001; r2 = 0.935, P < .001), center of pressure mean velocity (r1 = 0.982, P < .001; r2 = 0.935, P < .001), ellipse radius 1 (r1 = 0.979, P < .001; r2 = 0.965, P < .001), ellipse radius 2 (r1 = 0.982, P < .001; r2 = 0.969, P < .001), and ellipse area (r1 = 0.983, P < .001; r2 = 0.969, P < .001). Data from this case study suggest that VRSway measurements are highly correlated with output from force plate technology posing that VRSway is a novel approach to evaluate balance measures with VR. More research is required to understand possible uses of VR-based use for balance measurement in a larger and more diverse cohort.

Assessment of gait and posture characteristics using a smartphone wearable system for persons with osteoporosis with and without falls

We used smartphone technology to differentiate the gait characteristics of older adults with osteoporosis with falls from those without falls. We assessed gait mannerism and obtained activities of daily living (ADLs) with wearable sensor systems (smartphones and inertial measurement units [IMUs]) to identify fall-risk characteristics. We recruited 49 persons with osteoporosis: 14 who had a fall within a year before recruitment and 35 without falls. IMU sensor signals were sampled at 50 Hz using a customized smartphone app (Lockhart Monitor) attached at the pelvic region. Longitudinal data was collected using MoveMonitor+ (DynaPort) IMU over three consecutive days. Given the close association between serum calcium, albumin, PTH, Vitamin D, and musculoskeletal health, we compared these markers in individuals with history of falls as compared to nonfallers. For the biochemical parameters fall group had significantly lower calcium (P = 0.01*) and albumin (P = 0.05*) and higher parathyroid hormone levels (P = 0.002**) than nonfall group. In addition, persons with falls had higher sway area (P = 0.031*), lower dynamic stability (P < 0.001***), gait velocity (P = 0.012*), and were less able to perform ADLs (P = 0.002**). Thus, persons with osteoporosis with a history of falls can be differentiated by using dynamic real-time measurements that can be easily captured by a smartphone app, thus avoiding traditional postural sway and gait measures that require individuals to be tested in a laboratory setting.

Chest-Based Wearables and Individualized Distributions for Assessing Postural Sway in Persons with Multiple Sclerosis.

Typical assessments of balance impairment are subjective or require data from cumbersome and expensive force platforms. Researchers have utilized lower back (sacrum) accelerometers to enable more accessible, objective measurement of postural sway for use in balance assessment. However, new sensor patches are broadly being deployed on the chest for cardiac monitoring, opening a need to determine if measurements from these devices can similarly inform balance assessment. Our aim in this work is to validate postural sway measurements from a chest accelerometer. To establish concurrent validity, we considered data from 16 persons with multiple sclerosis (PwMS) asked to stand on a force platform while also wearing sensor patches on the sacrum and chest. We found five of 15 postural sway features derived from the chest and sacrum were significantly correlated with force platform-derived features, which is in line with prior sacrum-derived findings. Clinical significance was established using a sample of 39 PwMS who performed eyes-open, eyes-closed, and tandem standing tasks. This cohort was stratified by fall status and completed several patient-reported measures (PRM) of balance and mobility impairment. We also compared sway features derived from a single 30-second period to those derived from a one-minute period with a sliding window to create individualized distributions of each postural sway feature (ID method). We find traditional computation of sway features from the chest is sensitive to changes in PRMs and task differences. Distribution characteristics from the ID method establish additional relationships with PRMs, detect differences in more tasks, and distinguish between fall status groups. Overall, the chest was found to be a valid location to monitor postural sway and we recommend utilizing the ID method over single-observation analyses.

The relationship between body sway patterns and motor and attentional functions in early childhood.

[Purpose] We focused on the relationship between body sway patterns and motor and attentional functions in early childhood, and classified diagrams of body sway into four patterns. Furthermore, the relationship between physical fitness tests and Interactive Metronome (IM) tasks was used to determine whether the body sway patterns are indicators of motor and attentional functions in early childhood. [Participants and Methods] Participants were 24 male and 26 female children with a mean age of 2,148.1 ± 103.7 days. Participants were evaluated using physical fitness tests, body sway measures, baseline scores on the IM task (the "task average"), and the percentage of perfect hits ("Super Right On") on the IM task (the "Super Right On" score, or SRO%). [Results] The association between the body sway pattern and motor and attentional functions was examined, and results revealed that the body sway pattern was only slightly associated with motor functions. However, participants with an anterior-posterior pattern of body sway had worse timing and attentional functions than participants with other patterns, as indicated by a lower task average and SRO% on the IM task. [Conclusion] These results suggested that anterior-posterior sway may reflect attentional functions when body sway is measured in children such as 6 year-olds.

Feasibility of Combining Disease-Specific and Balance-Related Measures as Risk Predictors of Future Falls in Patients with Parkinson's Disease.

Evidence supports the view that postural sway in a quiet stance increases with clinical disease severity and dopaminergic therapy in idiopathic Parkinson’s disease (PD), which, in turn, increases the risk of falling. This study evaluated the feasibility of combining disease-specific and balance-related measures as risk predictors for future falls in patients with PD. The patients with PD underwent postural sway measurements (area, length, and velocity traveled by the excursion of the center of pressure) and clinical functional scores (Parkinson’s Disease Rating Scale [UPDRS] and Tinetti balance and gait score assessment) in both the on- and off-states of dopaminergic therapy. The outcome was defined as the development of a new fall. The sway area, velocity, and length increased after the medication administration. The Cox proportional hazards model showed that only previous fall history, Tinetti balance and gait score (on-state), and levodopa equivalent daily dose (LEDD) were associated with the development of future falls. The cumulative risk of fall development showed that the sway length and velocity were associated with future falls after more than six months. The combined LEDD, Tinetti balance and gait score (on-state), and velocity and length of postural sway (on-state) had the highest diagnostic accuracy (area under the curve = 0.9, p < 0.0001). Dopaminergic therapy can improve clinical functional scores but worsen balance-related measures. Increased sway length and velocity during the medication state are hallmarks of future falls, particularly in advanced PD. Combining disease-specific and balance-related measures can serve as an auxiliary diagnosis as risk predictors for future falls.

Overcoming the Limitations of the Berg Balance Scale (BBS)

Research Objectives To increase the sensitivity of the BBS tasks to effectively determine and track the falls risk of individuals. Design The BBS is commonly used to measure falls risk in older adults, but can only be utilized during face-to-face assessments. Due to COVID-19, a virtual health method of assessing falls risk in older adults is necessary. Markerless motion capture was used to provide a quantitative approach to static and dynamic elements of the BBS. This new protocol was dubbed the Enhanced Virtual BBS, or eV-BBS. The eV-BBS provides significantly more objective information than the current BBS, thereby improving its sensitivity and reproducibility. Setting University of Alberta Rehab Robotics Lab, Edmonton, Canada, during the COVID-19 pandemic. Participants A convenience sample of 10 healthy participants were selected. Interventions A test-retest reliability model determined the inter- and intra-participant variability when conducting the sit-to-stand and balance test in the BBS. Main Outcome Measures Novel parameters were created to represent the characteristics of the sit-to-stand and balance components of the BBS, such as rise height, drop height, and root mean square of trunk sway. Results The study revealed significant test-retest reliability (ICC = 0.81 to 0.99) and repeatability (COV < 20%) for the static stability tasks. The sensitivity of the eV-BBS to detect changes between participants was revealed during the analysis of the dynamic stability tasks, which had poor reliability (ICC = 0.10 to 0.60) and repeatability (COV > 20%). Conclusions The results indicate that the current BBS focuses on qualitative measures of sway and task timing. The dynamic and static components (of the sit-to-stand test in particular) are not identified, yet we know these are critical to assessing falling risk. The variability seen in the dynamic data of eV-BBS is likely to be attributable to subtle differences in participant performance of the task. Sensitivity of eV-BBS is high, but the level of sensitivity needed will only become apparent when participants at risk for falling are included in a future study. Author(s) Disclosures The authors have no conflicts of interest to declare. To increase the sensitivity of the BBS tasks to effectively determine and track the falls risk of individuals. The BBS is commonly used to measure falls risk in older adults, but can only be utilized during face-to-face assessments. Due to COVID-19, a virtual health method of assessing falls risk in older adults is necessary. Markerless motion capture was used to provide a quantitative approach to static and dynamic elements of the BBS. This new protocol was dubbed the Enhanced Virtual BBS, or eV-BBS. The eV-BBS provides significantly more objective information than the current BBS, thereby improving its sensitivity and reproducibility. University of Alberta Rehab Robotics Lab, Edmonton, Canada, during the COVID-19 pandemic. A convenience sample of 10 healthy participants were selected. A test-retest reliability model determined the inter- and intra-participant variability when conducting the sit-to-stand and balance test in the BBS. Novel parameters were created to represent the characteristics of the sit-to-stand and balance components of the BBS, such as rise height, drop height, and root mean square of trunk sway. The study revealed significant test-retest reliability (ICC = 0.81 to 0.99) and repeatability (COV < 20%) for the static stability tasks. The sensitivity of the eV-BBS to detect changes between participants was revealed during the analysis of the dynamic stability tasks, which had poor reliability (ICC = 0.10 to 0.60) and repeatability (COV > 20%). The results indicate that the current BBS focuses on qualitative measures of sway and task timing. The dynamic and static components (of the sit-to-stand test in particular) are not identified, yet we know these are critical to assessing falling risk. The variability seen in the dynamic data of eV-BBS is likely to be attributable to subtle differences in participant performance of the task. Sensitivity of eV-BBS is high, but the level of sensitivity needed will only become apparent when participants at risk for falling are included in a future study.

Keeping balance during head-free smooth pursuit: The role of aging

Standing balance is often more unstable when visually pursuing a moving target than when fixating on a stationary one. These effects are common in both young and older adults when the head is restrained during visual task performance. The present study focused on the role of head motion on standing balance during smooth pursuit as a function of age. Three predictions were tested: a) standing balance is compromised to a greater extent in older than young adults by gaze target pursuit compared to fixation, b) older adults pursue a moving target with greater and more variable head rotation than young adults, and c) greater and more variable head rotation during the smooth pursuit task is associated with greater Center of Pressure (CoP) sway. Twenty-two (22) older (age: 71.7 ± 8.1, 12 M / 10 F) and twenty-three (23) young adults (age: 23.6 ± 2.5, 12 M / 11 F) stood on a force plate while either fixating a stationary or smoothly pursuing a horizontally moving target (31.9° peak-to-peak visual angle). CoP (Bertec Balance Plate), head kinematics (Vicon Motion Analysis) and head-unconstrained gaze (Pupil Labs Invisible) were synchronously recorded. The root means square (RMS) of CoP velocity increased during smooth pursuit compared to fixation regardless of age (p < .05), while the interquartile CoP range increased only in older and not in young participants (p < .05). We also calculated the head rotation range (peak to peak cycle amplitude) of motion and variability (SD of range of motion) across the cycles of the smooth pursuit task. Older adults pursued the moving target employing more variable (p = .022) head yaw rotation than young participants although the mean range of head rotation was similar between groups (p =. 077). The amplitude and variability of head yaw rotation did not correlate with CoP sway measures. Results suggest that head-free pursuing of a moving target decreased balance to a greater extent in old than young individuals when compared to fixation. Nevertheless, postural sway during head-free smooth pursuit was not associated with the extent or variability of head rotation.

The association of fear of movement and postural sway in people with low back pain.

Fear of movement is thought to interfere with the recovery from low back pain (LBP). To date, the relationship between fear of movement and postural balance has not been adequately elucidated. Recent findings suggest that more specific fears need to be assessed and put in relation to a specific movement task. We propose that the fear to bend the trunk in a certain direction is distinctly related to the amount of postural sway in different directions. Therefore, our aim was to investigate whether fear of movement in general and fear of bending the trunk in a certain plane is related to postural sway. Data was collected from participants with LBP during two assessments ~3 weeks apart. Postural sway was measured with a force-platform during quiet standing with the eyes closed. Fear of movement was assessed with an abbreviated version of the Tampa Scale of Kinesiophobia (TSK-11) and custom items referring to fear of bending the trunk in the sagittal and the frontal plane. Based on data from 25 participants, fear of bending the trunk in the frontal plane was positively related to displacement in the sagittal and frontal plane and to velocity in the frontal plane (χ 2 = 4.35, p = 0.04; χ 2 = 8.15, p = 0.004; χ 2 = 9.79, p = 0.002). Fear of bending the trunk in the sagittal plane was not associated with any direction specific measure of sway. A positive relation of the TSK-11 with velocity of the frontal plane (χ 2 = 7.14, p = 0.008) was found, but no association with undirected measures of sway. Fear of bending the trunk in the frontal plane may be especially relevant to postural sway under the investigated stance conditions. It is possible that fear of bending the trunk in the frontal plane could interfere with balance control at the hip, shifting the weight from side to side to control balance. For the first time the directional relationship of fear of movement and postural sway was studied. Fear of bending the trunk in the frontal plane was positively associated with several measures of postural sway.

The Instrumented Stand and Walk (ISAW) test to predict falls in older men

Objective measures of balance and gait have the potential to improve prediction of future fallers because balance and gait impairments are common precursors. We used the Instrumented Stand and Walk Test (ISAW) with wearable, inertial sensors to maximize the domains of balance and gait evaluated in a short test. We hypothesized that ISAW objective measures across a variety of gait and balance domains would improve fall prediction beyond history of falls and better than gait speed or dual-task cost on gait-speed. We recruited 214 high-functioning older men (mean 82 years), of whom 91 participants (42.5%) had one or more falls in the 12 months following the ISAW test. The ISAW test involved 30 s of stance followed by a 7-m walk, turn, and return. We examined regression models for falling using 17 ISAW metrics, with and without age and fall history, and characterize top-performing models by AUC and metrics included. The ISAW test improved distinguishing between future fallers and non-fallers compared to age and history of falls, alone (AUC improved from 0.69 to 0.75). Models with 1 ISAW metric usually included a postural sway measure, models with 2 ISAW measures included a turning measure, models with 3 ISAW measures included a gait variability measure, and models with 4 or 5 measures added a gait initiation measure. Gait speed and dual-task cost did not distinguish between fallers and non-fallers in this high-functioning cohort. The best fall-prediction models support the notion that older people may fall due to a variety of balance and gait impairments.

Relationships among postural stability, physical fitness, and shooting accuracy in Olympic female goalball players.

This study aims to examine the relationship between postural perfor-mance, physical fitness level, and shooting performance in Olympic fe-male goalball players. Eight Olympic-level goalball players (age: 20.63± 4.37 years) were recruited from the Turkish National Women's Goalball Team. Postural stability, physical fitness, and shooting performance of the players were measured. The postural stability was determined us-ing body sway measurements during parallel and single-leg stances on a force plate. The physical fitness level of the players is evaluated by curl-up, isometric push-up, trunk lift, and grip strength (dominant hand) tests. A goalball-specific shooting accuracy test was used for shooting performance. Independent sample t-test and Pearson correlation were used for statistical processing. No statistical difference was observed in body sway parameters between open eyes and closed eyes condi-tions except for the anteroposterior sway area. Some of the body sway parameters performed under different stances positively correlated with all physical fitness tests (P<0.05). There was a positive correlation between the shooting accuracy and trunk lift score (r=0.767). Right leg sway area anterior-posterior and ellipse area negatively correlated with shooting accuracy (r=-0.629 and r=-0.692 respectively). It is necessary to attach importance to the improvement of the physical fitness level specific to core strength to maintain postural stability for visually im-paired athletes. In our study, some factors affecting shooting accuracy were identified, but it is necessary not to restrict a complex structure such as shooting accuracy within certain concepts.

Postural control in Parkinsonisms during a short static sway

Neurological diseases, such as Parkinsonisms, are often associated with static postural instability. Progressive supranuclear palsy (PSP) is a rare neurodegenerative disease classified among atypical Parkinsonisms. In the earliest stages, PSP is similar to Parkinson’s disease (PD) [1]. Static postural stability is an important contributor to the balance control framework and balance impairment can be quantified with a postural sway measure [2]. The main goal of our study was to compare postural sway changes in both PSP and PD subjects, using a standing single task of 5-6 seconds, in order to prove that a shorter sway time may be useful to distinguish Parkinsonisms. We assessed fifteen individuals with early PSP and fifteen individuals with recent diagnosis of PD (De Novo PD). Stabilometric analysis was performed for the evaluation of balance through a BTS Bioengineering system. The patient was instructed to stand on the force plate with the eyes open and measures of 5-6 seconds were taken. To find differences between the groups, univariate statistical analysis on sway data was conducted, and an alpha significance level was set to p-value < 0.05. The statistical analysis showed significant differences between De Novo PD and PSP groups for Medio- Lateral (M-L) sway (p-value=0.01), M-L range (p-value=0.023) and radius (p-value=0.026); minimum oscillation from the center of gravity and area showed a statistical trend with a p-value slightly above the 0.05 (p-value=0.056 and p-value=0.061, respectively). Several studies have demonstrated that balance dysfunction in PD is directionally dependent [2,3]. In agreement with our data, patients with atypical Parkinsonism show balance impairment on M-L direction as attested by augmented M-L sway, M-L range and radius. These results indicate that a short static sway of 5-6 seconds, could provide the clinician with a reliable and non-invasive tool to distinguish PSP from PD since the earliest stages.

TEST–RETEST RELIABILITY OF POSTURAL SWAY MEASURES DURING STATIC STANDING BALANCE PERFORMANCE IN HEALTHY ELDERLY ADULTS

Little is known about the reliability of postural sway measures in healthy elderly adults. Moreover, there is no standardized balance test protocols such as an efficient number of repeated measurements for older people. Therefore, we investigated test-retest reliability of center of pressure (COP) variables during static balance performance in elderly adults. Twenty-five elderly adults (15 elderly men and 10 elderly women) were asked to perform quiet standing balance test on a self-developed force platform. COP-based variables, i.e., COP mean distance, sway area, mean velocity, mean frequency, maximum frequency, and maximum power amplitude were derived from the COP data. For the test-retest reliability of each COP-based variable, intraclass correlation coefficient (ICC) was assessed in two-trials and three-trials of balance test. Mean velocity showed the highest ICC values in all directions (ICC = 0.832–0.922). Frequency domain variables presented lower reliability than time domain variables. Additionally, elderly adults did not affect the number of repeated measurements in most postural balance variables. These results suggest that time domain variables are more reliable variables than frequency domain variable and that balance test of two trials might be rather effective for elderly adults. These findings can be used to develop an optimal protocol of static balance test and select postural balance variables for elderly adults.

How Much Data Is Enough? A Reliable Methodology to Examine Long-Term Wearable Data Acquisition in Gait and Postural Sway.

Wearable sensors facilitate the evaluation of gait and balance impairment in the free-living environment, often with observation periods spanning weeks, months, and even years. Data supporting the minimal duration of sensor wear, which is necessary to capture representative variability in impairment measures, are needed to balance patient burden, data quality, and study cost. Prior investigations have examined the duration required for resolving a variety of movement variables (e.g., gait speed, sit-to-stand tests), but these studies use differing methodologies and have only examined a small subset of potential measures of gait and balance impairment. Notably, postural sway measures have not yet been considered in these analyses. Here, we propose a three-level framework for examining this problem. Difference testing and intra-class correlations (ICC) are used to examine the agreement in features computed from potential wear durations (levels one and two). The association between features and established patient reported outcomes at each wear duration is also considered (level three) for determining the necessary wear duration. Utilizing wearable accelerometer data continuously collected from 22 persons with multiple sclerosis (PwMS) for 6 weeks, this framework suggests that 2 to 3 days of monitoring may be sufficient to capture most of the variability in gait and sway; however, longer periods (e.g., 3 to 6 days) may be needed to establish strong correlations to patient-reported clinical measures. Regression analysis indicates that the required wear duration depends on both the observation frequency and variability of the measure being considered. This approach provides a framework for evaluating wear duration as one aspect of the comprehensive assessment, which is necessary to ensure that wearable sensor-based methods for capturing gait and balance impairment in the free-living environment are fit for purpose.

Postural Control Deficits And Type 2 Diabetes: A Meta-analysis Of Observational Studies

Type 2 diabetes patients often present diabetic peripheral neuropathy (DPN), and have an increased risk of falling. However, high fall incidence is also found in diabetic people without DPN. PURPOSE: To explore the association between postural control deficits and type2 diabetes beyond DPN. METHODS: We searched Pubmed, Embase, Medline, Web of Science, and Cochrane Library entries up to November 2021, using keywords including “diabetes” and “postural control” and their synonym. Cohort studies, case-control studies, and cross-sectional studies assessing the postural control of type 2 diabetes patients without DPN, and compared to non-diabetic controls were included. Center of pressure (COP)-based measures of postural sway were the primary outcome. Data were extracted by 2 independent reviewers and analyzed using STATA version 14.0. Random-effect models were applied to estimate the effect size with 95% confidence intervals (CIs), and I2 was used to evaluate the heterogeneity. RESULTS:Thirteen studies met the inclusion criteria, and 602 people (299 type 2diabetes patients and 303 healthy individuals) were included. Type 2 diabetes led to standing postural deficits on the floor with visual support (SMD = 1.25, 95% CI 0.70-1.1.79, P = 0.000, I2 = 88.4%), standing on floor without visual support (SMD = 1.18, 95%CI 0.63-1.84, P = 0.000, I2 = 89.7%), standing on foam with visual support (SMD = 1.03, 95%CI 0.21-1.84,P = 0.014, I2 = 87.0%), and standing on foam without visual support (SMD = 1.30, 95%CI 0.43-2.18,P = 0.004, I2 = 90.0%). Subgroup analysis demonstrated that postural sway increased significantly in patients with a diabetes duration of ≥5 years (SMD = 0.88, 95%CI 0.38-1.38, P = 0.001), BMI < 24.9 kg/m2 (SMD = 1.38, 95%CI 0.15-2.6, P = 0.028), and age < 50 years (SMD = 2.33, 95%CI 1.04-3.62, P = 0.000). CONCLUSIONS: Current literature indicates that postural control deficits are significantly associated with type 2 diabetes beyond DPN. Interestingly, this association is more evident in patients with a younger age or a normal BMI.

MODALITY OF PRACTICE AFFECTS BALANCE IMPROVEMENT WHILE LEARNING TO MOVE WITH A KNEE CRUTCH

PURPOSE: This study determined the impact of practice time and modality of practice on Balance while wearing a knee crutch (KC) on dominant leg, which gives a participant a “Peg Leg” like situation to move around. METHODS: Fifteen female (five in each group) and fifteen male (five in each group) participants were randomly assigned to one of three practice groups: Walking (W), Balance Training (BT), Combination (WBT). Four five-minute practice sessions were completed with balance tested before wearing KC, immediately after putting KC on, after each practice session, and after taking KC off. Balance was calculated as the average distance of three center of pressure measures of body sway during 20 second trials. A 7(time) x 3 (group) Mixed ANOVA followed by a Scheffe multiple comparisons (SMC) were done. RESULTS: ANOVA indicated a significant Time (F(6,162)=88.441, p < .001) and Group (F(2,27)=5.120, p=.013) main effects with significant interaction (F(12,162)=2.744, p = .002). SMC indicated that WBT (53.6 + 14.1 cm, 51.6 + 9.9 cm, 45.6 + 8.0 cm) was significantly different from the BT (36.9 + 4.7 cm, 36.4 + 5.6 cm, 38.4 + 6.0 cm) and W (41.0 + 7.0 cm, 40.7 + 6.4 cm, 35.8 + 3.4 cm) groups following the last three practice sessions (P < .045). The BT and W groups were not significantly different throughout the tests (P > .456). CONCLUSION: Balance appears to improve more efficiently with a consistent modality rather than mixing modalities.

Vertical ground reaction force oscillation during standing on hard and compliant surfaces: The "postural rhythm".

When a person stands upright quietly, the position of the Centre of Mass (CoM), the vertical force acting on the ground and the geometrical configuration of body segments is accurately controlled around to the direction of gravity by multiple feedback mechanisms and by integrative brain centres that coordinate multi-joint movements. This is not always easy and the postural muscles continuously produce appropriate torques, recorded as ground reaction force by a force platform. We studied 23 young adults during a 90 s period, standing at ease on a hard (Solid) and on a compliant support (Foam) with eyes open (EO) and with eyes closed (EC), focusing on the vertical component of the ground reaction force (VGRF). Analysis of VGRF time series gave the amplitude of their rhythmic oscillations (the root mean square, RMS) and of their frequency spectrum. Sway Area and Path Length of the Centre of Pressure (CoP) were also calculated. VGRF RMS (as well as CoP sway measures) increased in the order EO Solid ≈ EC Solid < EO Foam < EC Foam. The VGRF frequency spectra featured prevailing frequencies around 4–5 Hz under all tested conditions, slightly higher on Solid than Foam support. Around that value, the VGRF frequencies varied in a larger range on hard than on compliant support. Sway Area and Path Length were inversely related to the prevailing VGRF frequency. Vision compared to no-vision decreased Sway Area and Path Length and VGRF RMS on Foam support. However, no significant effect of vision was found on VGRF mean frequency for either base of support condition. A description of the VGRF, at the interface between balance control mechanisms and sway of the CoP, can contribute information on how upright balance is maintained. Analysis of the frequency pattern of VGRF oscillations and its role in the maintenance of upright stance should complement the traditional measures of CoP excursions in the horizontal plane.

102. An introductory investigation of standing postural control ‘error’ and its relation to balance in adult spinal deformity surgery patients

102. An introductory investigation of standing postural control ‘error’ and its relation to balance in adult spinal deformity surgery patients

Apathy exacerbates postural control impairments in stroke survivors: The potential effects of cognitive dual-task for improving postural control

Apathy is a stressor and debilitating common condition for both stroke survivors and their caregivers. However, its effects on the postural control of these patients have not yet been investigated. Improved postural stability through withdrawing attention from postural control by concurrent cognitive task (i.e. dual-task condition) has been reported previously, but the effect of apathy, as a confounding factor, remains unknown. This study aimed to examine the effects of apathy and dual-task condition on postural control of chronic stroke survivors from biomechanical and neurophysiological perspectives. Twenty non-apathetic stroke survivors, 20 apathetic stroke survivors, and 20 sex-, age-, weight-, and height-matched healthy subjects were assessed using different postural sway measures and electromyography activity of ankle and hip muscles while quietly standing on rigid and foam surfaces under single-task, easy dual-task, and difficult dual-task conditions. The results showed postural instability and neuromuscular stiffening of stroke survivors, particularly apathetic stroke survivors, compared with healthy controls as evidenced by significantly greater postural sway measures and increased co-contraction of ankle muscles as well as hip muscles. Notably, concurrently performing a cognitive task significantly reduced postural instability and neuromuscular stiffening in chronic stroke survivors even in those with apathy. In conclusion, apathy exacerbates postural control impairments in chronic stroke survivors promoting an inefficient conscious mode of postural control. It is recommended that distracting the attention away from postural control by performing a concurrent cognitive task can be considered an effective strategy while designing interventions for improving postural control in apathetic stroke survivors.

The influence of a vibrotactile biofeedback system on postural dynamics during single-leg standing in healthy older adults

The effectiveness of sensory substitution technology, such as haptic-based vibrotactile biofeedback (VBF), has been verified for balance training and rehabilitation. However, whether VBF training changes postural dynamics in older people remains unknown. This study investigated the influence of VBF training on postural dynamics during single-leg standing in older adults, using detrended fluctuation analysis (DFA). Twenty older adults participated in this study. Measurement of postural sway comprised three phases: first measurement session as a baseline test, postural training (day 1), and second measurement session (day 2). The BF group received BF training during the balance training session, while the control group practiced single-leg stance without BF. The center of pressure (CoP) trajectory was recorded in the first measurement session (pre) and second measurement session (post) at 50 Hz. DFA revealed the presence of two linear scaling regions in the CoP, indicating the presence of fast- and slow-scale fluctuations. For the BF group, slow-scale postural dynamics revealed more anti-persistent behavior after training in the anterior-posterior direction. However, the control group showed a change toward more random dynamics after training. These different influences suggest that the BF system might improve error correction strategies during single-leg standing for older adults, while single-leg standing training without the BF system might cause the loss of controllability in single-leg standing. Further, the results of the DFA are discussed in the context of balance training using VBF.