Characteristics of Unsuccessful Balance Reactive Responses to Lateral Loss of Balance in Older Adults.

INTRODUCTION: An effective reactive step response to an unexpected balance loss is an important factor that determines if a fall will happen. We investigated reactive step strategies and kinematics of unsuccessful balance recovery responses that ended with falls in older adults. METHODS: We compared the strategies and kinematics of reactive stepping after a lateral loss of balance, i.e., perturbations, between 49 older female adults who were able to successfully recover from perturbations (perturbation-related non-fallers, PNFs) and 10 female older adults who failed to recover (perturbation-related fallers, PFs). In addition, we compared the successful versus unsuccessful recovery responses of PFs matched to perturbation magnitude. RESULTS: The kinematics of the first reactive step response were significantly different between PFs and PNFs, i.e., longer initiation time, step time, swing time, and time to peak swing-leg velocity, larger first-step length, and center-of-mass displacement. Incomplete crossover stepping and leg collision were significant causes of falls among PFs. Similar findings were found when we compared the successful versus unsuccessful recovery responses of PFs. CONCLUSIONS: The crossover step, which requires a complex coordinated leg movement, resulted in difficulty in controlling and decelerating the moving center of mass following a lateral perturbation, affecting the kinematics of the stepping response, leading to a fall.

Automated Loss-of-Balance Event Identification in Older Adults at Risk of Falls during Real-World Walking Using Wearable Inertial Measurement Units.

Loss-of-balance (LOB) events, such as trips and slips, are frequent among community-dwelling older adults and are an indicator of increased fall risk. In a preliminary study, eight community-dwelling older adults with a history of falls were asked to perform everyday tasks in the real world while donning a set of three inertial measurement sensors (IMUs) and report LOB events via a voice-recording device. Over 290 h of real-world kinematic data were collected and used to build and evaluate classification models to detect the occurrence of LOB events. Spatiotemporal gait metrics were calculated, and time stamps for when LOB events occurred were identified. Using these data and machine learning approaches, we built classifiers to detect LOB events. Through a leave-one-participant-out validation scheme, performance was assessed in terms of the area under the receiver operating characteristic curve (AUROC) and the area under the precision recall curve (AUPR). The best model achieved an AUROC ≥0.87 for every held-out participant and an AUPR 4-20 times the incidence rate of LOB events. Such models could be used to filter large datasets prior to manual classification by a trained healthcare provider. In this context, the models filtered out at least 65.7% of the data, while detecting ≥87.0% of events on average. Based on the demonstrated discriminative ability to separate LOBs and normal walking segments, such models could be applied retrospectively to track the occurrence of LOBs over an extended period of time.

High-Specificity Digital Architecture for Real-Time Recognition of Loss of Balance Inducing Fall.

Falls are a significant cause of loss of independence, disability and reduced quality of life in people with Parkinson's disease (PD). Intervening quickly and accurately on the postural instability could strongly reduce the consequences of falls. In this context, the paper proposes and validates a novel architecture for the reliable recognition of losses of balance situations. The proposed system addresses some challenges related to the daily life applicability of near-fall recognition systems: the high specificity and system robustness against the Activities of Daily Life (ADL). In this respect, the proposed algorithm has been tested on five different tasks: walking steps, sudden curves, chair transfers via the timed up and go (TUG) test, balance-challenging obstacle avoidance and slip-induced loss of balance. The system analyzes data from wireless acquisition devices that capture electroencephalography (EEG) and electromyography (EMG) signals. The collected data are sent to two main units: the muscular unit and the cortical one. The first realizes a binary ON/OFF pattern from muscular activity (10 EMGs) and triggers the cortical unit. This latter unit evaluates the rate of variation in the EEG power spectrum density (PSD), considering five bands of interest. The neuromuscular features are then sent to a logical network for the final classification, which distinguishes among falls and ADL. In this preliminary study, we tested the proposed model on 9 healthy subjects (aged 26.3 ± 2.4 years), even if the study on PD patients is under investigation. Experimental validation on healthy subjects showed that the system reacts in 370.62 ± 60.85 ms with a sensitivity of 93.33 ± 5.16%. During the ADL tests the system showed a specificity of 98.91 ± 0.44% in steady walking steps recognition, 99.61 ± 0.66% in sudden curves detection, 98.95 ± 1.27% in contractions related to TUG tests and 98.42 ± 0.90% in the obstacle avoidance protocol.

Types of falls and strategies for maintaining stability on an unstable surface.

BACKGROUND: Falls constitute an important health issue. They cause significant morbidity, mortality and have marked psychological effects on the individual, too. The aim of this study has been to determine parameters describing human movement strategies for balance and the reaction if balance is lost as a result of an unstable ground, and to attempt to describe the types of falls. MATERIAL AND METHODS: The study group comprised 20 volunteers. Kinematic parameters of falling and dynamic stability were measured using the Vicon Motion System and the Biodex Balance System SD. During the test, subjects stood for 20 s on the tilting platform. The analysis was conducted based on the first recordings, when the participants were not prepared for the event and their reactions were natural. A cluster analysis tool was applied to divide the behavior of people during the test. RESULTS: Based on motion range for kinematic parameters, the cluster analysis revealed 2 types of human behavior: falling (stepping) and restoring balance. Two types of falls were also observed: side and back falls. Moreover, on the basis of angular values for tilting plate, 4 zones were determined. The frequency of access to these zones by each joint revealed 3 strategies to maintain balance: ankle, knee and hip strategy. CONCLUSIONS: A set of initial conditions that may be used for future numerical simulations was also determined. Furthermore, the results presented in this study are likely to support the analysis of the effects and the falling patterns. Med Pr 2018;69(3):245-252.

Reactive stepping behaviour in response to forward loss of balance predicts future falls in community-dwelling older adults.

BACKGROUND: a fall occurs when an individual experiences a loss of balance from which they are unable to recover. Assessment of balance recovery ability in older adults may therefore help to identify individuals at risk of falls. The purpose of this 12-month prospective study was to assess whether the ability to recover from a forward loss of balance with a single step across a range of lean magnitudes was predictive of falls. METHODS: two hundred and one community-dwelling older adults, aged 65-90 years, underwent baseline testing of sensori-motor function and balance recovery ability followed by 12-month prospective falls evaluation. Balance recovery ability was defined by whether participants required either single or multiple steps to recover from forward loss of balance from three lean magnitudes, as well as the maximum lean magnitude participants could recover from with a single step. RESULTS: forty-four (22%) participants experienced one or more falls during the follow-up period. Maximal recoverable lean magnitude and use of multiple steps to recover at the 15% body weight (BW) and 25%BW lean magnitudes significantly predicted a future fall (odds ratios 1.08-1.26). The Physiological Profile Assessment, an established tool that assesses variety of sensori-motor aspects of falls risk, was also predictive of falls (Odds ratios 1.22 and 1.27, respectively), whereas age, sex, postural sway and timed up and go were not predictive. CONCLUSION: reactive stepping behaviour in response to forward loss of balance and physiological profile assessment are independent predictors of a future fall in community-dwelling older adults. Exercise interventions designed to improve reactive stepping behaviour may protect against future falls.

Vestibular deficits leading to disequilibrium and falls in ambulatory amyotrophic lateral sclerosis.

OBJECTIVE: To assess vestibular deficits in response to disequilibrium in ambulatory individuals with amyotrophic lateral sclerosis (ambALS). DESIGN: All participants completed standard protocols for the Sensory Organization Test (SOT) by computerized dynamic posturography. SETTING: Multidisciplinary amyotrophic lateral sclerosis clinic at an academic medical center. PARTICIPANTS: Study participants (N=34) consisted of ambALS (n=19) and healthy controls (HC) (n=15). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Equilibrium scores (ESs) obtained from averaged sway amplitude in condition 5 (ES5) and condition 6 (ES6) of the SOT. RESULTS: In conditions of altered somatosensory information with vision absent or vision sway-referenced, the mean ± SD scores for ambALS (ES5=51.4±22.5; ES6=50.8±22.1) were lower than those for HC (ES5=65.4±11.7, P≤.03; ES6=58.9±12.5, P>.05). Seven ambALS (37%) experienced a total of 19 falls during the sway-referenced support test conditions. There were no falls in the HC. CONCLUSIONS: Nearly 37% of ambALS with normal clinical balance testing have decreased ability to use the vestibular input and required increased reliance on visual input for postural orientation to sustain equilibrium. The mechanism of this alteration in sensory preference is not completely clear. Extrapyramidal involvement early in ALS may be indicated.

Wrist-worn voice recorders capture the circumstances and context of losses of balance among community-dwelling older adults.

BACKGROUND: Most falls among community-dwelling older adults are due to a loss of balance (LOB) after tripping or slipping. Unfortunately, limited insight is available on the detailed circumstances and context of these LOBs. Moreover, commonly used methods to collect this information is susceptible to limitations of memory recall. The goal of this pilot observational study was to explore the circumstances and context of self-reported LOBs captured by wrist-worn voice recorders among community-dwelling older adults. METHODS: In this pilot observational cohort study, 30 community-dwelling adults with a mean (SD) age of 71.8 (4.4) years were asked to wear a voice recorder on their wrist daily for 3 weeks. Following any naturally-occurring LOB, participants were asked to record their verbal responses to six questions regarding the circumstances and context of each LOB abbreviated with the mnemonic 4WHO: When, Where, What, Why, How, and Outcome. RESULTS: Participants wore the voice recorder 10.9 (0.6) hours per day for 20.7 (0.5) days. One hundred seventy-five voice recordings were collected, with 122 meeting our definition of a LOB. Each participant reported 0-23 LOBs over the 3 weeks or 1.4 (2.1) per participant per week. Across all participants, LOBs were most commonly reported 3 p.m. or later (42%), inside the home (39%), while walking (33%), resulting from a trip (54%), and having induced a stepping response to regain balance (48%). No LOBs resulted in a fall. CONCLUSIONS: Among community-dwelling older adults, wrist-worn voice recorders capture the circumstances and context of LOBs thereby facilitating the documentation of detail of LOBs and potentially falls, without reliance on later recall.

Lower-limb inter-joint coordination during balance recovery after trips.

BACKGROUND: Trips are one of the most common external perturbations that can lead to accidental falls. Knowledge about postural control attributes of balance recovery after trips could help reveal the biomechanical causes for trip-induced falls and provide implications for fall prevention interventions. RESEARCH QUESTION: The objective of the present study was to examine coordinated lower-limb movements during balance recovery after trips. METHODS: One hundred and twenty-three volunteers participated in an experimental study. They were tripped unexpectedly by a metal pole when walking on a linear walkway at their self-selected speed. Lower-limb inter-joint coordination quantified by continuous relative phase measures, including the mean of the absolute relative phases (MARP) and the deviation phase (DP), was analyzed during the execution of the first recovery step after unexpected trips. RESULTS: Compared to unsuccessful balance recovery, smaller MARPknee-ankle and DPknee-ankle of successful recovery were observed with distal inter-joint coordination on the swing side. Inter-joint coordination of the stance limb did not significantly differ between successful and unsuccessful recovery conditions. These findings indicate that the control of the swing limb's distal joints is crucial for regaining balance after trips. SIGNIFICANCE: An implication derived from this study is that greater in-phase coordination and smaller coordination variability in distal joints of the swing limb could be considered as potential targets for interventions aimed at preventing trip-induced accidental.

Kinematic Measures for Recovery Strategy Identification following an Obstacle-Induced Trip in Gait.

This study aimed to identify the kinematic measures determining balance outcome following an over-ground trip perturbation. 117 healthy older adults who experienced laboratory-induced trips were divided into loss of balance (LOB) and no LOB groups. The LOB group contained 27 fallers and 34 non-fallers, and the no LOB group contained 21 participants using cross-over strategy and 35 participants using obstacle-hit strategy. A 2-class hierarchical regression model for balance loss showed that margin of stabilty could determine the balance outcomes (LOB or not) with an overall accuracy of 92.7%. The 4-class model for recovery strategies showed that the combination of margin of stability, trunk angle, and COM velocity could determine 81.9% of strategies. Our findings would enhance intervention development for populations at risk of trip-induced falls.

Patient-reported involvement of the eighth cranial nerve in giant cell arteritis.

INTRODUCTION: The frequency of eighth nerve lesions in patients with giant cell arteritis (GCA) has rarely been examined. However, sudden onset deafness has been recorded as a presenting feature of GCA on several occasions. This study sought to establish how common this and other symptoms of eighth nerve involvement are in a large retrospective survey. METHODS: We contacted 170 patients with GCA and 250 matched PMR patients, inviting them to participate in a questionnaire survey of symptoms of eighth nerve dysfunction. We compared the presence of deafness, tinnitus, loss of balance and vertigo in both groups and examined the relationship between the onset of these symptoms and other features of GCA. RESULTS: A total of 317 patients were recruited. The percentage of patients with symptoms of possible vestibulocochlear disease prior to commencement of steroid therapy was significantly greater among GCA patients than PMR patients for all domains. Hearing loss which was twice as common in GCA as in PMR (53% vs 26%) [p = 0.001]. Deafness was concurrent in 35% of GCA patients with other symptoms and 45% reported colocation with headache. Recovery with steroids occurred in 56% of these. CONCLUSION: Symptoms of eighth nerve dysfunction are present in over half of patients with GCA. Recovery with steroids was predicted by concurrence with headache in terms of both timing and location. It appears that eighth nerve involvement, especially acute hearing loss, is a not infrequent feature of GCA and often responds well to steroid therapy. Clinicians should enquire about these symptoms when evaluating a patient for possible GCA.Key Points• Deafness is a frequent presenting feature of giant cell arteritis.• Vertigo, tinnitus and loss of balance are also often reported by GCA sufferers.• Steroid therapy is more likely to relieve these symptoms if they are ipsilateral and concurrent with headache.

[Effectiveness of vestibular rehabilitation in patients with vestibular dysfunction]. / Ocena skutecznosci rehabilitacji przedsionkowej u pacjentów z dysfunkcja blednika.

BACKGROUND: Vertigo and instability due to vestibular dysfunction have been a frequent cause of work absence, with a clearly upward tendency observed in recent years. Uncompensated vestibular hypofunction requires vestibular rehabilitation, but access to this form of treatment remains limited. Therefore, innovative methods of rehabilitation utilizing new technologies, which could promote this therapy, are searched for. Virtual reality (VR) is becoming a popular method of rehabilitation used, for example, in the treatment of stroke or schizophrenia. The aim of this study was to compare and evaluate 2 methods of vestibular rehabilitation in patients with unilateral vestibular disorders. MATERIAL AND METHODS: Forty-three patients with unilateral vestibular disorders diagnosed at the Balance Disorders Unit, 1st Otolaryngology Department of the Medical University of Lodz, were included in this study. The patients, divided into 2 groups, received 10 sessions of rehabilitation. Group 1 (N = 22) was rehabilitated using a VR unit consisting of a forceplate and a motion sensor, while Group 2 (N = 21) performed training on a static posturography platform under physiotherapist supervision. The patients were examined at the baseline, 1 month and 3 months after rehabilitation. During each assessment, posturography was performed which recorded the center of pressure (CoP) displacement. The patients also filled out a questionnaire to quantify vertigo symptoms. RESULTS: The CoP parameters decreased in both groups, with no superiority of either form of training. Analysis of the subjective symptoms reduction revealed a decrease in the Vertigo Syndrome Scale - short form (VSS-sf) score in the second evaluation in both groups, which was slightly greater in the VR group. The improvement remained stable 3 months after rehabilitation. CONCLUSIONS: Both forms of rehabilitation are effective in increasing postural stability and reducing subjective symptoms. Virtual reality training achieves a slightly greater subjective improvement. Med Pr. 2019;70(5):545-53.

Effects of Heat Exposure from Live-Burn Fire Training on Postural Stability of Firefighters.

Firefighters perform physically intensive jobs in suboptimal environments, making it even more important for them to maintain good functional postural balance or stability. As part of their training, firefighters are required to perform physically demanding tasks under high stress and high heat environments. These demanding tasks lead to increased physical fatigue which can then result in poor performance and/or postural instability. The objectives of this study were to 1) investigate the effect of live-firefighting training-induced heat stress on static postural balance, and 2) investigate the association between commonly monitored physiological responses (core body temperature, heart rate, oxygen saturation and blood pressure) and measures of static postural balance. Twenty-six firefighters (mean ± SD: age 36.0 years ±5.2, weight 216 lbs. ± 34, BMI 29.7 ± 4.2) participated in live firefighting training while performing following tasks: search and rescue, hose advancement, and backup. Prior to heat exposure (PRE) and following each scenario (POST1, POST2, POST3), firefighters' postural balance was assessed with a wearable 3-D inertial sensor system quantifying time dependent changes in linear acceleration (LIN ACC) and angular velocity (AV) about three orthogonal axes [Anterior-Posterior (AP), Medial-Lateral (ML), and vertical (V)] during one foot balance tests for 30 seconds under eyes open and eyes closed conditions. The outcome variables from 3-D wearable sensors were used to create 3-D Phase-Plane based postural stability metrics. Physiological measurement of core body temperature (CBT) (measured with a radio pill) as well as perception of heat increased significantly during the live fire-training exercise. In addition, firefighters also perceived an increase in physical fatigue and respiratory distress. Angular combined stability parameters (ACSP), RMS angular velocity around ML axis were significantly correlated with CBT. In the multivariate analysis adjusted for the scenarios, height and weight of the firefighters, these measures of static postural balance were significantly associated with CBT. As per the model results, static postural balance, as indicated by ACSP, worsened with an increase in CBT. Future studies should place sensors at body extremities along with close to center of mass to capture the kinematic movements more comprehensively influencing postural balance.

Falls-risk post-stroke: Examining contributions from paretic versus non paretic limbs to unexpected forward gait slips.

Community-dwelling stroke survivors show a high incidence of falls with unexpected external perturbations during dynamic activities like walking. Previous evidence has demonstrated the importance of compensatory stepping to restore dynamic stability in response to perturbations in hemiparetic stroke survivors. However, these studies were limited to either stance perturbations or perturbation induced under the unaffected limb. This study aimed to compare the differences, if any, between the non-paretic and paretic sides in dynamic stability and protective stepping strategies when exposed to unexpected external perturbation during walking. Twenty hemiparetic subjects experienced an unexpected forward slip during walking on the laboratory walkway either on the paretic (n=10) or the nonparetic limb (n=10). Both groups demonstrated a backward loss of balance with a compensatory stepping response, with the nonparetic-side slip group resorting mainly to an aborted step response (60%) and the paretic-side slip group mainly exhibiting a recovery step response (90%). Although both groups showed an equal incidence of falls, the nonparetic-side slip group demonstrated a higher stability at recovery step touchdown, resulting from lower perturbation magnitudes (slip displacement and velocity) compared to the paretic-side slip group. The results indicate that the paretic side had difficulty initiating and executing a successful stepping response (nonparetic-side slip) and also in reactive limb control while in stance (paretic-side slip). Based on these results it is suggested that intervention strategies for fall-prevention in chronic stroke survivors should focus on paretic limb training for both reactive stepping and weight bearing for improving balance control for recovery from unpredictable perturbations during dynamic activities such as walking.

Dynamic stability and compensatory stepping responses during anterior gait-slip perturbations in people with chronic hemiparetic stroke.

To examine the control of dynamic stability and characteristics of the compensatory stepping responses to an unexpected anterior gait slip induced under the non-involved limb in people with hemi-paretic stroke (PwHS) and to examine any resulting adaptive changes in these on the second slip due to experience from prior slip exposure. Ten PwHS experienced overground slip (S1) during walking on the laboratory walkway after 5-8 regular walking (RW) trials followed by a second consecutive slip trial (S2). The slip outcome (backward loss of balance, BLOB and no loss of balance, NLOB) and COM state (i.e. its COM position and velocity) stability were examined between the RW and S1 and S1 and S2 at touchdown (TD) of non-involved limb and at liftoff (LO) of the contralateral limb. At TD there was no difference in stability between RW and S1, however at LO, subjects demonstrated a lower stability on S1 than RW resulting in a 100% backward loss of balance (BLOB) with compensatory stepping response (recovery step, RS, 4/10 or aborted step, AS, 6/10). On S2, although there was no change in stability at TD, there was a significant improvement in stability at LO with a 40% decrease in BLOB. There was also a change in step strategy with a decrease in AS response (60% to 35%, p<0.05) which was replaced by an increase in the ability to step (increased compensatory step length, p<0.05) either via a recovery step or a walkover step. PwHS have the ability to reactively control COM state stability to decrease fall-risk upon a novel slip; prior exposure to a slip did not significantly alter feedforward control but improved the ability to use such feedback control for improved slip outcomes.

Decreased lower limb muscle recruitment contributes to the inability of older adults to recover with a single step following a forward loss of balance.

In response to a balance disturbance, older individuals often require multiple steps to prevent a fall. Reliance on multiple steps to recover balance is predictive of a future fall, so studies should determine the mechanisms underlying differences between older adults who can and cannot recover balance with a single step. This study compared neural activation parameters of the major leg muscles during balance recovery from a sudden forward loss of balance in older individuals capable of recovering with a single step and those who required multiple steps to regain balance. Eighty-one healthy, community dwelling adults aged 70±3 participated. Loss of balance was induced by releasing participants from a static forward lean. Participants performed four trials at three initial lean magnitudes and were subsequently classified as single or multiple steppers. Although step length was shorter in multiple compared to single steppers (F=9.64; p=0.02), no significant differences were found between groups in EMG onset time in the step limb muscles (F=0.033-0.769; p=0.478-0.967). However, peak EMG normalised to values obtained during maximal voluntary contraction was significantly higher in single steppers in 6 of the 7 stepping limb muscles (F=1.054-4.167; p=0.045-0.024). These data suggest that compared to multiple steppers, single steppers recruit a larger proportion of the available motor unit pool during balance recovery. Thus, modulation of EMG amplitude plays a larger role in balance recovery than EMG timing in this context.