Balance strategies for recovery from perturbed overground walking.

Bipedal locomotion is naturally unstable and requires active control. Walking is believed to be primarily stabilized through the selection of foot placements; however, other strategies are available, including regulation of ankle inversion/eversion, ankle push-off, and angular momentum through trunk postural adjustments. The roles of these strategies in maintaining overall stability are often masked by the dominant foot placement strategy. The objectives of this study were to describe how the four strategies are used to respond to medial or lateral ground perturbations during overground walking in healthy individuals and determine reliance on each strategy. Fifteen healthy adults walked with and without perturbations applied to the right foot at heel strike while body kinematics and surface electromyographic activity were measured. Medial perturbations resulted in decreased step width on the first step after the perturbation, increased ankle inversion, increased ankle push-off, and rightward trunk sway. Lateral perturbations resulted in increased step width, decreased ankle inversion, no change in ankle push-off, and leftward trunk sway. EMG activity was consistent with the observed strategies (e.g. increased peroneus longus EMG activity during ankle eversion) with the exception of increased bilateral erector spinae activity for all perturbations. Foot placement was the dominant strategy in response to perturbations, with other strategies showing reduced, yet significant, roles. This work demonstrates that multiple strategies are recruited to improve the balance response in addition to foot placement alone. These results can serve as a reference for future studies of populations with impaired balance to identify potential deficits in strategy selection.

A Common Data Element-Based Adjudication Process for mTBI Clinical Profiles: A Targeted Multidomain Clinical Trial Preliminary Study.

INTRODUCTION: The primary purpose of this study was to examine the prevalence and percent agreement of clinician-identified mild traumatic brain injury (mTBI) clinical profiles and cutoff scores for selected Federal Interagency Traumatic Brain Injury Research common data elements (CDEs). A secondary purpose was to investigate the predictive value of established CDE assessments in determining clinical profiles in adults with mTBI. MATERIALS AND METHODS: Seventy-one (23 males; 48 females) participants (M = 29.00, SD = 7.60, range 18-48 years) within 1-5 months (M = 24.20, SD = 25.30, range 8-154 days) of mTBI completed a clinical interview/exam and a multidomain assessment conducted by a licensed clinician with specialized training in concussion, and this information was used to identify mTBI clinical profile(s). A researcher administered CDE assessments to all participants, and scores exceeding CDE cutoffs were used to identify an mTBI clinical profile. The clinician- and CDE-identified clinical profiles were submitted to a multidisciplinary team for adjudication. The prevalence and percent agreement between clinician- and CDE-identified clinical profiles was documented, and a series of logistic regressions with adjusted odds ratios were performed to identify which CDE assessments best predicted clinician-identified mTBI clinical profiles. RESULTS: Migraine/headache, vestibular, and anxiety/mood mTBI clinical profiles exhibited the highest prevalence and overall percent agreement among CDE and clinician approaches. Participants exceeding cutoff scores for the Global Severity Index and Headache Impact Test-6 assessments were 3.90 and 8.81 times more likely to have anxiety/mood and migraine/headache profiles, respectively. The Vestibular/Ocular Motor Screening vestibular items and the Pittsburgh Sleep Quality Index total score were predictive of clinician-identified vestibular and sleep profiles, respectively. CONCLUSIONS: The CDEs from migraine/headache, vestibular, and anxiety/mood domains, and to a lesser extent the sleep modifier, may be clinically useful for identifying patients with these profiles following mTBI. However, CDEs for cognitive and ocular may have more limited clinical value for identifying mTBI profiles.

Comparison of physiological outcomes after dynamic exertion between athletes at return to sport from concussion and controls: Preliminary findings.

OBJECTIVES: Compare physiological (heart rate, heart rate variability, and blood pressure), performance (change-of-direction task completion time and errors), and clinical (symptoms and rating of perceived exertion) outcomes during dynamic exertion between athletes at return to sport after concussion to healthy athlete controls. DESIGN: Case control. METHODS: A sample of 23 (Female = 10; 43.5 %) athletes at medical clearance to play/activity from concussion (CONCUSS) and 23 sex-, age-, and sport-matched healthy athletes (CONTROLS) completed a 5-min seated rest before and after the dynamic exertion test. Independent sample t-tests were used to compare CONCUSS and CONTROLS for completion time, heart rate, and blood pressure; and Mann-Whitney U tests for symptoms, perceived exertion, and errors. A series of ANOVAs were conducted to compare heart rate variability between groups across pre- and post-exercise rest periods. RESULTS: There were no differences in heart rate, blood pressure, symptoms, perceived exertion, and errors. CONCUSS were faster on Zig Zag (p = .048) and Pro Agility (p = .018) tasks, reported lower symptom severity (p = .019), and had lower post-EXiT HRV (p < .049) than CONTROLS. CONCLUSIONS: Performance, symptoms, perceived exertion, and blood pressure outcomes from dynamic exertion were equivocal between athletes at medical clearance from concussion and healthy controls, which provide empirical support for dynamic exercise to inform medical clearance clinical decision making for sport-related concussion. However, differences in autonomic nervous system functioning indicate that additional research is needed to examine temporal changes in heart rate variability and other physiological outcomes following dynamic exertion.

Head and vestibular kinematics during vertical semicircular canal impulses.

BACKGROUND: The video head impulse test (vHIT) is a common assessment of semicircular canal function during high-speed impulses. Reliability of the vHIT for assessing vertical semicircular canals is uncertain. Vertical head impulses require a complex head movement, making it difficult to isolate a single semicircular canal and interpret resulting eye rotations. OBJECTIVE: The purpose of this study was to provide descriptive head kinematics and vestibular stimuli during vertical plane impulses to ultimately improve impulse delivery and interpretation of vHIT results for vertical semicircular canals. METHODS: Six participants received right anterior (RA) and left posterior (LP) semicircular canal impulses. Linear displacements, rotational displacements, and rotational velocities of the head were measured. Peak velocities in semicircular canal planes and peak-to-peak gravitoinertial accelerations at the otolith organs were derived from head kinematics. RESULTS: The largest rotational velocities occurred in the target semicircular canal plane, with non-negligible velocities occurring in non-target planes. Larger vertical displacements and accelerations occurred on the right side of the head compared to the left for RA and LP impulses. CONCLUSIONS: These results provide a foundation for designing protocols to optimize stimulation applied to a singular vertical semicircular canal and for interpreting results from the vHIT for vertical semicircular canals.

Correction: Bohlke et al. The Effect of a Verbal Cognitive Task on Postural Sway Does Not Persist When the Task Is Over. Sensors 2021, 21, 8428.

There was an error in the original publication [...].

Exercise interventions, postural control, and prefrontal cortex activation in older adults.

Improving postural control in older adults is necessary for reducing fall risk, and prefrontal cortex activation may also play a role. We sought to examine the impact of exercise interventions on postural control and prefrontal cortex activation during standing balance tasks. We hypothesized that balance would improve and prefrontal control would be reduced. We assessed a subset of participants enrolled in a randomized trial of two exercise interventions. Both groups completed strength and endurance training and the experimental treatment arm included training on timing and coordination of stepping. Postural control and prefrontal cortex activation were measured during dual-task standing balance tasks before and after the intervention. Eighteen participants in the standard strengthening and mobility training arm and 16 in the timing and coordination training arm were included. We examined pre- to post-intervention changes within each study arm, and compared them between interventions. Results did not show any pre- to post-intervention changes on standing postural control nor prefrontal cortex activation in either arm. In addition, there were no differences between the two intervention arms in either balance or prefrontal activation. While exercise interventions can improve mobility, we do not demonstrate evidence of improved standing balance or prefrontal control in standing.

The Psychometric Properties of the 9-Item Vestibular Activities Avoidance Instrument.

OBJECTIVE: The purpose of this study was to establish the psychometric properties of the 9-Item Vestibular Activities Avoidance Instrument (VAAI-9), a patient-reported outcome measure developed to identify fear avoidance beliefs in persons with vestibular disorders. METHODS: This prospective cohort study included 100 participants 18 years and older seeking care at a balance disorders clinic for dizziness. Participants completed the VAAI-9, the Dizziness Handicap Inventory (DHI), and other patient-reported outcomes at the initial visit and the 3-month follow-up. To measure test-retest reliability, the VAAI-9 was completed again 5 days after the initial visit and was analyzed using a 2-way mixed ICC for absolute agreement. Internal consistency was determined using the Cronbach alpha. The Spearman correlation coefficient was used to assess convergent validity of the VAAI-9 with other outcomes. Receiver operating characteristic curves were used to identify baseline VAAI-9 cutoff scores for those who reported mild (DHI ≤ 30) or moderate or severe (DHI > 30) perceived disability at the 3-month follow-up. RESULTS: The mean age of the study cohort was 49 (SD = 16) years; 73 (73%) were women. Seventy-one participants completed the 5-day follow-up, and 68 completed the 3-month follow-up. The VAAI-9 demonstrated excellent internal consistency (α = 0.91) and test-retest reliability (ICC = 0.90). Baseline VAAI-9 scores had moderate to strong associations with other outcome measures at baseline and 3 months. A baseline VAAI-9 score of 26 or higher had a sensitivity of 80.6% and a specificity of 78.4% for identifying a DHI score of >30 at 3 months (area under the curve = 0.86). CONCLUSIONS: The results provide evidence of excellent reliability and validity for the 9-item VAAI in persons with vestibular disorders. A baseline VAAI-9 score of ≥26 identified individuals at risk of persistent moderate to severe disability due to dizziness. IMPACT: Initial levels of fear avoidance beliefs measured using the VAAI-9 provided important prognostic information about outcomes for persons with vestibular symptoms.

Test-Retest, Interrater Reliability, and Minimal Detectable Change of the Dynamic Exertion Test (EXiT) for Concussion.

BACKGROUND: The Dynamic Exertion Test (EXiT) was developed to inform return-to-play (RTP) decision-making following clinical recovery from sport-related concussion (SRC). The purpose of the current study was to document intrarater and test-retest reliability and minimal detectable change (MDC) scores for physiological [heart rate (HR) and blood pressure], performance (change-of-direction task completion time and errors), and clinical outcomes (endorsed symptoms, perceived exertion) of EXiT, and interrater reliability of performance outcomes. HYPOTHESIS: Healthy athletes would exhibit stable physiological responses to the EXiT across visits, demonstrate consistent change-of-direction task completion time between consecutive trials at each visit, and the fastest time (of 2 trials) across visits, and endorse equivocal symptoms and effort across visits. STUDY DESIGN: Cross-sectional, test-retest. LEVEL OF EVIDENCE: Level 3. METHODS: Seventy-nine (female: 34 [43%], 19.6 ± 5.0 years) athletes completed the EXiT at 2 study visits (8.7 ± 4.7 days between visits). Two-way, mixed, intraclass correlation coefficients (ICCs) were used to evaluate intrarater and test-retest reliability. Cronbach's alpha was used to document the internal consistency of symptoms at each visit, and MDC scores were calculated on the physiological, performance, and clinical outcomes. RESULTS: Measured and percentage of age-estimated maximum HR were reliable following EXiT (ICC = 0.579-0.618). Change-of-direction task completion time (MDC range = 0.75-8.70 s) had good-to-excellent test-retest (ICC = 0.703-0.948) and interrater (ICC = 0.932-0.965) reliability. Symptoms had a high internal consistency at visits 1 (α = 0.894) and 2 (α = 0.805) and were reliable across visits (ICC = 0.588). CONCLUSION: The current investigation established test-retest reliability in addition to MDC scores of an objective dynamic exercise assessment among healthy adolescent and adult athletes. The EXiT may be an objective approach to inform RTP decision-making following SRC recovery. CLINICAL RELEVANCE: The EXiT is a clinically feasible exertion-based assessment that can be readily administered in a variety of outpatient clinical settings.

Rating of perceived difficulty scale for measuring intensity of standing balance exercises in individuals with vestibular disorders.

BACKGROUND: A method for prescribing the difficulty or intensity of standing balance exercises has been validated in a healthy population, but requires additional validation in individuals with vestibular disorders. OBJECTIVE: This study validated the use of ratings of perceived difficulty for estimation of balance exercise intensity in individuals with vestibular disorders. METHODS: Eight participants with a confirmed diagnosis of a vestibular disorder and 16 healthy participants performed two sets of 16 randomized static standing exercises across varying levels of difficulty. Root Mean Square (RMS) of trunk angular velocity was recorded using an inertial measurement unit. In addition, participants rated the perceived difficulty of each exercise using a numerical scale ranging from 0 (very easy) to 10 (very difficult). To explore the concurrent validity of rating of perceived difficulty scale, the relationship between ratings of perceived difficulty and sway velocity was assessed using multiple linear regression for each group. RESULTS: The rating of perceived difficulty scale demonstrated moderate positive correlations RMS of trunk velocity in the pitch (r = 0.51, p < 0.001) and roll (r = 0.73, p < 0.001) directions in participants with vestibular disorders demonstrating acceptable concurrent validity. CONCLUSIONS: Ratings of perceived difficulty can be used to estimate the intensity of standing balance exercises in individuals with vestibular disorders.

The Role of Age, Sex, Body Mass Index, and Sport Type on the Dynamic Exertion Test in Healthy Athletes: A Cross-Sectional Study.

BACKGROUND: The dynamic exertion test (EXiT) was developed to help inform return to play after sport-related concussion, but some factors may threaten the internal validity of EXiT and affect clinical interpretation. OBJECTIVE: To compare age, sex, BMI, and sport types across EXiT physiological [pre-EXiT and post-EXiT percentage of maximum heart rate (HR %max) and blood pressure (BP)], performance (change-of-direction task completion time and committed errors), and clinical [symptoms and rating of perceived exertion (RPE)] outcomes among healthy adolescents and adults. STUDY DESIGN: Cross-sectional. METHODS: Eighty-seven participants ( F = 55, 37.4%) reported symptoms and RPE during the EXiT, which consists of a 12-minute treadmill running protocol, and the dynamic circuit, ball toss, box shuffle (SHUF) and carioca (CAR), zig zag (ZZ), proagility (PA), and arrow agility (AA) tasks. Independent samples t tests were conducted for pre-EXiT and post-EXiT HR %max and BP and change-of-direction task completion time and Mann-Whitney U tests for errors, symptoms, and RPE. A series of 1-way analysis of variance (ANOVAs) and Kruskal-Wallis H tests were conducted to compare collision, contact, and noncontact sport types. RESULTS: Adolescents had lower completion time across AA ( P = 0.01) and male athletes lower than female athletes on CAR, ZZ, PA, and AA ( P < 0.04). Male athletes reported greater RPE after the SHUF, CAR, and AA ( P < 0.03). HR %max , errors, and symptoms were equivocal across all subgroups ( P > 0.05). CONCLUSION: Age and sex should be considered in the interpretation of performance and clinical, but not physiological, EXiT outcomes. The EXiT is a standardized exercise assessment and generalizable to healthy athletes.

Impact of strength and balance on Functional Gait Assessment performance in older adults.

BACKGROUND: The Functional Gait Assessment (FGA) evaluates postural stability in gait and predicts fall risk in older adults. Individual tasks within the FGA consider aspects of mobility assumed to require strength and/or balance to complete. Identifying how quantitative measures of strength and balance relate to FGA performance would allow for more targeted interventions based on one's pattern of performance on different tasks. RESEARCH QUESTION: Is performance on the FGA (total score and individual task scores) related to measures of strength and balance in healthy older adults? METHODS: In a cross-sectional study, healthy older adults (N = 46) were evaluated with the FGA, measures of knee extensor strength, and balance (static stance and weight shifting) (N = 46). Correlational analyses were performed between FGA scores (total and individual) and measures of strength and balance. RESULTS: Total FGA performance was positively correlated with knee extensor strength (maximum torque and rate of torque development). Individual FGA tasks of walking backwards (task 9) and stair climbing (task 10) had the highest correlations with strength measures. Total FGA performance was correlated with reduced postural sway in static balance tasks, but not with balance performance on the weight shifting tasks. The individual FGA task that challenged proprioceptive (task 7) inputs for balance was associated with static balance. SIGNIFICANCE: The total FGA score is related to domains of strength and static balance. The results indicate that the FGA can be influenced by reduced strength and balance. The pattern of performance on individual FGA tasks may indicate whether reduced postural stability in gait is related to deficits in strength or balance domains in this older population.

The Effect of a Verbal Cognitive Task on Postural Sway Does Not Persist When the Task Is Over.

Dual-task balance studies explore interference between balance and cognitive tasks. This study is a descriptive analysis of accelerometry balance metrics to determine if a verbal cognitive task influences postural control after the task ends. Fifty-two healthy older adults (75 ± 6 years old, 30 female) performed standing balance and cognitive dual-tasks. An accelerometer recorded movement from before, during, and after the task (reciting every other letter of the alphabet). Thirty-six balance metrics were calculated for each task condition. The effect of the cognitive task on postural control was determined by a generalized linear model. Twelve variables, including anterior-posterior centroid frequency, peak frequency and entropy rate, medial-later entropy rate and wavelet entropy, and bandwidth in all directions, exhibited significant differences between baseline and cognitive task periods, but not between baseline and post-task periods. These results indicate that the verbal cognitive task did alter balance, but did not bring about persistent effects after the task had ended. Traditional balance measurements, i.e., root mean square and normalized path length, notably lacked significance, highlighting the potential to use other accelerometer metrics for the early detection of balance problems. These novel insights into the temporal dynamics of dual-task balance support current dual-task paradigms to reduce fall risk in older adults.

Utility of a Postural Stability/Perceptual Inhibition Dual Task for Identifying Concussion in Adolescents.

CONTEXT: Research in the area of dual-task paradigms to assess sport-related concussion (SRC) status is growing, but additional assessment of this paradigm in adolescents is warranted. DESIGN: This case-control study compared 49 adolescent athletes aged 12-20 years with diagnosed SRC to 49 age- and sex-matched controls on visual-spatial discrimination and perceptual inhibition (PIT) reaction time tasks performed while balancing on floor/foam pad conditions. METHODS: The SRC group completed measures at a single time point between 1 and 10 days postinjury. Primary outcomes were dual-task reaction time, accuracy, and sway. General linear models evaluated differences between groups (P < .05). Logistic regression identified predictors of concussion from outcomes. Area under the curve evaluated discriminative ability of identifying SRC. RESULTS: Results supported significantly higher anterior-posterior (AP) sway values in concussed participants for visual-spatial discrimination and PIT when balancing on the floor (P = .03) and foam pad (P = .03), as well as mediolateral sway values on the floor during visual-spatial discrimination (P = .01). Logistic regression analysis (R2 = .15; P = .001) of all dual-task outcomes identified AP postural sway during the PIT foam dual task as the only significant predictor of concussed status (ß = -2.4; P = .004). Total symptoms (area under the curve = 0.87; P < .001) and AP postural sway on foam (area under the curve = 0.70; P = .001) differentiated concussed from controls. CONCLUSION: The AP postural sway on foam during a postural stability/PIT dual task can identify concussion in adolescents between 1 and 10 days from injury.

Fear Avoidance Beliefs Are Associated With Perceived Disability in Persons With Vestibular Disorders.

OBJECTIVE: The purpose of this study was to determine the association between fear-avoidance beliefs and disability in 3 months in people with vestibular disorders while accounting for demographic and clinical characteristics. METHODS: This prospective cohort study included people aged 18 to 100 years who reported dizziness. Participants were recruited from a balance disorders clinic and outpatient physical therapy clinics. All participants completed the Vestibular Activities Avoidance Instrument (VAAI) and the Hospital Anxiety and Depression Scale at baseline and the Vestibular Activities and Participation measure (VAP), dizziness Visual Analogue Scale (VAS), and 12-item Short Form Health Questionnaire at baseline and 3-month follow-up. A modified version of the VAAI included 9 items abstracted from the 81-item VAAI. The relationships between 9-item VAAI scores and follow-up measures of disability were assessed using Spearman correlation coefficients. Linear regression models were analyzed to determine the effect of fear-avoidance beliefs on follow-up VAP score while accounting for baseline outcome measures. RESULTS: All participants (n = 404) completed the baseline assessment (mean age = 54 years), and 286 (71%) completed the 3-month assessment. The mean 9-item VAAI score was 25 (SD = 14) at baseline and was significantly associated with VAP (ρ = 0.54), 12-item Short Form Health Questionnaire component scores (ρ = -0.53; -0.44), and dizziness VAS at follow-up (ρ = 0.37). Approximately 38% of the variation in VAP score at follow-up was predicted by age, number of medications, 9-item VAAI score, dizziness VAS, and Hospital Anxiety and Depression Scale-depression score when considered together (R2 = 0.38). CONCLUSION: Fear-avoidance beliefs are associated with measures of disability at 3 months and are predictive of activity limitations and participation restrictions at 3 months when controlling for age, medications, baseline dizziness, and depression symptom severity in people with vestibular disorders. IMPACT: Measurement of fear-avoidance beliefs may provide important prognostic information, suggesting that an assessment of fear-avoidance beliefs could be used by clinicians to identify individuals at greater risk of disability after a vestibular disorder. LAY SUMMARY: Fear-avoidance beliefs in people who have vestibular disorders are associated with disability at 3 months and predict limitations in daily activities at 3 months.

Exploratory Factor Analysis of the Vestibular Activities Avoidance Instrument.

Importance: Fear avoidance is a behavioral response to dizziness that can lead to chronic symptoms and maladaptation of the vestibular system, but there is no valid and reliable clinical measure of fear avoidance for persons with dizziness. Although the Vestibular Activities Avoidance Instrument (VAAI) was developed to identify fear avoidance beliefs in persons with dizziness, it was considered too long for clinical use. Objective: To continue development of the VAAI for clinical use by reducing its length and by assessing the internal consistency and construct validity through associations with measures of disability, quality of life, and psychological well-being. Design, Setting, and Participants: This prospective cohort study conducted from February 2018 to December 2019 at a tertiary care balance disorders clinic and in outpatient physical therapy clinics in the United States included 404 adults with dizziness. Main Outcomes and Measures: Participants completed the 81-item VAAI, the Vestibular Activities and Participation (VAP) measure, the 12-Item Short Form Health Survey (SF-12), and the Hospital Anxiety and Depression Scale (HADS) at baseline. Exploratory factor analysis of the VAAI was conducted to reduce the number of items. Internal consistency of the reduced VAAI was determined by calculating the Cronbach α. Convergent validity was assessed by examining the associations between the reduced VAAI and the VAP, the SF-12, and the HADS using Spearman correlation coefficients. Results: Data from 404 adults (mean [SD] age, 54.0 [17.0] years; 64.6% women) were included in the analyses. The exploratory factor analysis indicated that 2 factors explained the underlying constructs of the 81-Item VAAI. The first factor was retained and measured the construct of fear avoidance. The VAAI was reduced to 9 items (VAAI-9). The VAAI-9 showed excellent internal consistency (Cronbach α = 0.92) and was positively associated with the VAP (ρ = 0.81) and the HADS anxiety (ρ = 0.47) and depression (ρ = 0.64) subscales, and negatively associated with physical (ρ = -0.76) and mental (ρ = -0.47) health-related quality of life. Conclusions and Relevance: These findings indicate that the VAAI-9 is a short, internally consistent, valid measure of fear avoidance and is associated with quality of life, activity limitations and participation restrictions, and psychological well-being. The next steps in the development of the VAAI-9 will include validation in an external sample, assessment of test-retest validity, and prospective investigations of its association with future disability.

Quantitative comparison of correction techniques for removing systemic physiological signal in functional near-infrared spectroscopy studies.

Significance: Isolating task-evoked brain signals from background physiological noise (e.g., cardiac, respiratory, and blood pressure fluctuations) poses a major challenge for the analysis of functional near-infrared spectroscopy (fNIRS) data. Aim: The performance of several analytic methods to separate background physiological noise from brain activity including spatial and temporal filtering, regression, component analysis, and the use of short-separation (SS) measurements were quantitatively compared. Approach: Using experimentally recorded background signals (breath-hold task), receiver operating characteristics simulations were performed by adding various levels of additive synthetic "brain" responses in order to examine the sensitivity and specificity of several previously proposed analytic approaches. Results: We found that the use of SS fNIRS channels as regressors of no-interest within a linear regression model was the best performing approach examined. Furthermore, we found that the addition of all available SS data, including all recorded channels and both hemoglobin species, improved the method performance despite the additional degrees-of-freedom of the models. When SS data were not available, we found that principal component filtering using a separate baseline scan was the best alternative. Conclusions: The use of multiple SS measurements as regressors of no interest implemented in a robust, iteratively prewhitened, general linear model has the best performance of the tested existing methods.

Shared neural substrates of cognitive function and postural control in older adults.

INTRODUCTION: Poor cognitive function and postural control co-occur in older adults. It is unclear whether they share neural substrates. METHODS: Postural sway error during a novel visual tracking (VT) condition and gray matter volume (GMV) were compared between participants with normal cognition (NC), mild cognitive impairment (MCI), or dementia (n = 179, mean age 82, 56% females, 56% white). Associations between VT error, cognitive function, and GMV were examined. RESULTS: Greater VT error was associated with having dementia compared to NC or MCI (odds ratio [95% CI] = 2.15 [1.38, 3.36] and 1.58 [1.05, 2.38]). Regions with lower GMV related to greater VT error and worse cognition were: bilateral hippocampi, parahippocampi, entorhinal, and parietal cortices (all P ≤0.05). GMV of bilateral hippocampi and left parahippocampus explained >20% of VT error between dementia and NC. DISCUSSION: Postural control during visuospatial tasks and dementia may share neural substrates, specifically memory-related regions.

Psychometric properties of instrumented postural sway measures recorded in community settings in independent living older adults.

BACKGROUND: In the last few decades, research related to balance in older adults has been conducted in lab-based settings. The lack of portability and high cost that is associated with the current gold standard methods to quantify body balance limits their application to community settings such as independent living facilities. The purpose of the study was to examine the relative and absolute reliability and the convergent validity of static standing balance performance using an accelerometer device. METHODS: A total of 131 participants (85% female, mean age 80 ± 8 years) were included for the validity aim, and a subsample of 38 participants were enrolled in the reliability testing (89% female, mean age 76 ± 7 years). The root-mean-square (RMS) and normalized path length (NPL) for sway in antero-posterior (AP) and medio-lateral (ML) directions were calculated for different standing balance conditions. Test-retest reliability was assessed over two testing visits occurring 1 week apart using the intraclass correlation coefficient (ICC) for relative reliability, and the minimal detectable change (MDC) was calculated for the absolute reliability. Spearman's rank correlation coefficient was used to test convergent validity at baseline between balance measurements and related mobility measures. RESULTS: Reliability of balance performance using accelerometers was good to excellent with ICC values ranging from 0.41 to 0.83 for RMS sway and from 0.49 to 0.82 for NPL sway. However, the ICC during semi-tandem stance in A-P direction was 0.35, indicating poor reliability. The MDC of the sway measurements ranged from 2.4 to 9.4 for the RMS and 5.2 to 13.8 for the NPL. Balance measurements were correlated with mobility measurements. CONCLUSIONS: Using a portable accelerometer to quantify static standing postural control provides reliable measurements in community settings.

Gray Matter Regions Associated With Functional Mobility in Community-Dwelling Older Adults.

BACKGROUND/OBJECTIVES: Neuroimaging indicators of reduced brain health in the form of lower gray matter volume (GMV), lower fractional anisotropy (FA), and higher white matter hyperintensity volume (WMHV) have been related to global mobility measures, such as gait speed, in older adults. The purpose was to identify associations between brain regions and specific mobility functions to provide a greater understanding of the contribution of the central nervous system to independent living. DESIGN: Cross-sectional study. SETTING: Research laboratory. PARTICIPANTS: Seventy community-ambulating healthy older adults (mean age = 76 ± 5 years). MEASUREMENTS: Participants performed the following tests: gait speed, Five Times Sit to Stand, Four Square Step Test (FSST), and Dynamic Gait Index (DGI). Structural magnetic resonance imaging of each participant's brain was collected. Measures of regional GMV, tract-specific WMHV, and FA were extracted. Correlational analyses between the mobility measures and neuroimaging measures were conducted using whole brain and regional and tract-specific measures. This was followed by linear regression models relating the mobility measures to regions or tracts identified in the correlation analysis, and adjusting for age, sex, and body mass index. RESULTS: Significant associations were found between higher GMV in multiple regions, primarily the parietal and temporal lobes, and better performance in gait speed, DGI, and FSST. After adjusting for personal factors, greater parahippocampus GMV was independently associated with greater gait speed. Greater inferior parietal lobe, supramarginal gyrus, and superior temporal gyrus GMVs were associated with gait function. Greater postcentral gyrus, parahippocampus, and superior temporal gyrus GMVs were associated with faster FSST performance. The WMHV and FA were not significantly correlated with the mobility measures. CONCLUSIONS: Gray matter regions associated with higher performance in mobility measures serving gait function and multidirectional stepping were those structures related to vestibular sensation, spatial navigation, and somatosensation. J Am Geriatr Soc 68:1023-1028, 2020.

Perception of verticality is altered in people with severe chronic low back pain compared to healthy controls: A cross-sectional study.

BACKGROUND: People with chronic low back pain (CLBP) have abnormal lumbar proprioception, which increases their reliance on visual input to maintain body verticality. Maintaining verticality is important for spatial orientation, balance and movement coordination. It is unknown if these patients also have altered perception of verticality. OBJECTIVE: To compare whether the perception of verticality is different between people with and without CLBP. DESIGN: Cross-sectional. METHODS: Two comparisons of perception of verticality were done between a group of people with CLBP (n = 25) and healthy people (n = 25); and between a subgroup of people with severe CLBP (n = 14) and healthy people (n = 25). In a dark room, the subjective visual vertical test was performed under 3 conditions: rod, rod-and-frame, and rod-and-disc. In each condition, the rod was tilted 40° clockwise and counterclockwise, and the participants were asked to bring it back to vertical 0° position. The rod deviation from verticality was recorded in degrees. RESULTS: When considering the CLBP group, analysis of variance showed that deviation from verticality had no significant group interaction with condition (p = 0.2), or group main effect (p = 0.2). However, deviation from verticality was significantly different between the conditions (p < 0.001). When considering the severe CLBP subgroup, the interaction effect was significant (p = 0.046). Simple main effects showed that the severe CLBP subgroup had larger deviations from verticality (7.5 ±â€¯0.9 deg) compared to the healthy group (4.2 ±â€¯0.7 deg) specifically on the rod-and-frame condition (p = 0.007). CONCLUSION: People with severe CLBP appear to have larger deviations in judging verticality compared to the healthy group.