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

Dual-task interference of reactive stepping kinematics for balance recovery strategies in older adults

OBJECTIVE

To characterize the interference of reactive stepping kinematics related to the increase or maintenance of the number of steps in response to a large perturbation during dual tasks among older adults.

METHODS

This was a cross-sectional study that included 52 community-dwelling healthy older adults. Reactive stepping performance was analyzed after forward balance loss during a single task and a second cognitive task. The number of steps taken to recover balance and dual-task interference (DTI) for muscular onset latency, anteroposterior (AP) center of pressure (COP) displacement and velocity before step initiation, and step temporal and spatial variables were measured. The DTI of the variables was compared between the participants who increased versus those who maintained the number of steps taken during the dual task relative to the single task.

RESULTS

Twenty-eight (53.8 %) participants increased their steps during dual tasks relative to a single task. In older adults, the AP COP peak velocity (P < 0.001) and step length (P < 0.001) were significantly worse during dual tasks than during a single task. However, this was not observed for older adults who did not increase their steps. The DTI for the AP COP peak velocity and step length were significantly larger for the older adults who increased their steps than those who did not (AP COP peak velocity; P = 0.044, step length; P = 0.003). Both groups showed a significant muscular onset delay during dual tasks than during a single task (P < 0.001), and no significant differences were found between the groups.

CONCLUSIONS

Our findings suggest that reactive stepping strategies in older adults after a large external perturbation during secondary cognitive tasks can be attributed to interference with COP control before step initiation and step length.

Baseline Measures of Physical Activity and Function Do Not Predict Future Fall Incidence in Sedentary Older Adults: A Prospective Cohort Study

Physical activity (PA) and physical function (PF) are modifiable risk factors for falls in older adults, but their ability to predict future fall incidence is unclear. The purpose of this study was to determine the predictive ability of baseline measures of PA, PF, and lower limb strength on future falls. A total of 104 participants underwent baseline assessments of PA, PF, and lower limb strength. Falls were monitored prospectively for 12 months. Eighteen participants fell at least once during the 12-month follow-up. Participants recorded almost exclusively sedentary levels of activity. PA, PF, and lower limb strength did not differ between fallers and nonfallers. Twelve participants, who reported a minor musculoskeletal injury in the past 6 months, experienced a fall. The results of this study suggest that in a cohort of highly functioning, sedentary older adults, PA does not distinguish fallers from nonfallers and that the presence of a recent musculoskeletal injury appears to be a possible risk factor for falling.

Challenges in Delivering Effective Care for Older Persons with Fragility Fractures

Fragility fractures occur because of low-impact trauma or even spontaneously in individuals with osteoporosis. Caring for older persons with fragility fractures can present several challenges due to the unique needs and vulnerabilities of this population. Older individuals commonly have multiple medical conditions, such as osteoporosis, arthritis, cardiovascular diseases, and diabetes. These comorbidities can complicate fracture management and increase the risk of complications. Fracture repair through surgery may be more complex in older patients due to poor bone quality, decreased tissue elasticity, and higher chances of anesthesia complications. In addition, mobility and functional limitations post-fracture are highly prevalent in this population, affecting their independence and increasing their risk of institutionalization. Addressing these challenges requires a multidisciplinary approach involving orthopedic surgeons, geriatricians, physical and rehabilitation physicians, physiotherapists, occupational therapists, dieticians, social workers, and caregivers. Preventive measures, such as fall prevention strategies and osteoporosis management, can also play a vital role in reducing the incidence of fragility fractures in older persons.

Use of Reactive Balance Assessments With Clinical Baseline Concussion Assessments in Collegiate Athletes

CONTEXT

Current clinical concussion evaluations assess balance deficits using static or dynamic balance tasks while largely ignoring reactive balance. Including a reactive balance assessment might provide a more comprehensive concussion evaluation.

OBJECTIVES

To identify redundancy in current clinical baseline assessments of concussion and determine whether reactive balance adds unique information to these evaluations.

DESIGN

Cross-sectional study.

SETTING

Clinical assessment.

PATIENTS OR OTHER PARTICIPANTS

A total of 279 healthy National Collegiate Athletic Association Division I athletes.

INTERVENTION(S)

Two cohorts of data were collected at the beginning of the athletic season. For cohort 1 (n = 191), the Immediate Post-Concussion Assessment and Cognitive Tool, instrumented modified push and release (I-mP&R), and Balance Error Scoring System (BESS) were administered. For cohort 2 (n = 88), the I-mP&R, BESS, timed tandem gait, walking with eyes closed, and clinical reaction time were administered.

MAIN OUTCOME MEASURE(S)

The strengths of the relationships between the Immediate Post-Concussion Assessment and Cognitive Tool cognitive indices, mP&R clinical score, instrumented measures (BESS sway; I-mP&R time to stability, latency, and step length), BESS score, timed tandem gait, walking time to completion, and clinical reaction time were characterized.

RESULTS

The strongest interinstrument correlation value was between single-task time to stability from the I-mP&R and clinical reaction time but was considered weak (r = 0.35, P = .001). The mP&R and I-mP&R clinical scores were weakly associated with the other assessments.

CONCLUSIONS

Weak correlations between interassessment variables indicated that little redundancy was present in the current clinical evaluations. Furthermore, reactive balance represents a unique domain of function that may improve the comprehensiveness of clinical assessments.

Trip-Related Fall Risk Prediction Based on Gait Pattern in Healthy Older Adults: A Machine-Learning Approach

Trip perturbations are proposed to be a leading cause of falls in older adults. To prevent trip-falls, trip-related fall risk should be assessed and subsequent task-specific interventions improving recovery skills from forward balance loss should be provided to the individuals at risk of trip-fall. Therefore, this study aimed to develop trip-related fall risk prediction models from one's regular gait pattern using machine-learning approaches. A total of 298 older adults (≥60 years) who experienced a novel obstacle-induced trip perturbation in the laboratory were included in this study. Their trip outcomes were classified into three classes: no-falls (n = 192), falls with lowering strategy (L-fall, n = 84), and falls with elevating strategy (E-fall, n = 22). A total of 40 gait characteristics, which could potentially affect trip outcomes, were calculated in the regular walking trial before the trip trial. The top 50% of features (n = 20) were selected to train the prediction models using a relief-based feature selection algorithm, and an ensemble classification model was selected and trained with different numbers of features (1-20). A ten-times five-fold stratified method was utilized for cross-validation. Our results suggested that the trained models with different feature numbers showed an overall accuracy between 67% and 89% at the default cutoff and between 70% and 94% at the optimal cutoff. The prediction accuracy roughly increased along with the number of features. Among all the models, the one with 17 features could be considered the best model with the highest AUC of 0.96, and the model with 8 features could be considered the optimal model, which had a comparable AUC of 0.93 and fewer features. This study revealed that gait characteristics in regular walking could accurately predict the trip-related fall risk for healthy older adults, and the developed models could be a helpful assessment tool to identify the individuals at risk of trip-falls.

Effects of Fear of Falling on the Single-Step Threshold for Lateral Balance Recovery in Older Women

BACKGROUND AND PURPOSE

Fear of falling is associated with poor physical health and influences postural stability during whole-body movement. The ability to recover from lateral balance loss is required to prevent falls; however, the relationship between lateral balance recovery and fear of falling has not been established. This study aimed to investigate whether fear of falling is associated with the stepping threshold for lateral balance recovery.

METHODS

This study included 56 ambulatory, community-dwelling women aged 65 years or older. We determined the single-step threshold as the maximum lean magnitude normalized with body weight from which participants could be suddenly released and still recover balance using a single side step. The short-form Falls Efficacy Scale International was used as a measure of fear of falling.

RESULTS AND DISCUSSION

The single-step threshold significantly correlated with age ( rs =-0.603) and the short-form Falls Efficacy Scale International score ( rs =-0.439). Ordinal regression analysis revealed that age (odds ratio, 0.826; 95% confidence interval, 0.742-0.920) and the short-form Falls Efficacy Scale International score (odds ratio, 0.811; 95% confidence interval, 0.680-0.966) were significantly associated with the single-step threshold, such that older age and greater fear of falling each independently predicted that failure to recover balance with a single step would occur at a lower percentage of body weight.

CONCLUSIONS

Greater fear of falling was associated with reduced ability to recover from lateral balance loss in addition to aging. Future studies should explore whether evidence-based interventions to reduce fear of falling combined with perturbation training might lead to improved ability to recover from balance loss.

Assessment of balance in people with mild traumatic brain injury using a balance systems model approach

PURPOSE

Measuring persistent imbalance after mTBI is challenging and may include subjective symptom-reporting as well as clinical scales. Clinical assessments for quantifying balance following mTBI have focused on sensory orientation. It is theorized that balance control goes beyond sensory orientation and also includes subdomains of anticipatory postural adjustments, reactive postural control, and dynamic gait. The Mini Balance Evaluation Systems Test (Mini-BESTest) is a validated balance test that measures balance according to these subdomains for a more comprehensive assessment. The purpose of this study was to compare Mini-BESTest total and subdomain scores after subacute mTBI with healthy controls.

METHODS

Symptomatic mTBI (n = 90, 20 % male, age=36.0 ± 12.0, 46.3.4 ± 22.1 days since injury) and healthy control (n = 45, 20 % male, age=35.4 ± 12.5) participants completed the Mini-BESTest for balance. Mini-BESTest between-group differences were evaluated using Wilcoxon rank-sum tests.

RESULTS

The mTBI group (Median[minimum,maximum]) had a significantly worse Mini-BESTest total score than the healthy controls (24[18,28] vs 27[23-28], p < 0.001). The mTBI group performed significantly worse in 3 of the 4 subdomains compared to the healthy controls: reactive postural control: 5[2-6] vs 6[3-6], p = 0.003; sensory orientation: 6[5,6] vs 6[6], p = 0.005; dynamic gait: 8[5-10] vs 9[8-10], p < 0.001. There was no significance difference between groups in the anticipatory postural adjustments domain (5[3-6] vs 5[3-6], p = 0.12).

CONCLUSIONS

The Mini-BESTest identified deficits in people with subacute mTBI in the total score and 3 out of 4 subdomains, suggesting it may be helpful to use in the clinic to identify balance subdomain deficits in the subacute mTBI population. In combination with self-reported assessments, the mini-BESTest may identify balance domain deficits in the subacute mTBI population and help guide treatment for this population.

Compensatory stepping responses during real-life falls in older adults

BACKGROUND

Laboratory studies of postural responses suggest that stepping is a common strategy for balance recovery. Yet little is known about the frequency and characteristics of stepping responses during real-life falls in older adults.

RESEARCH QUESTIONS

(1) Among falls experienced by older adults in long-term care (LTC), what is the prevalence of attempts to recover balance by stepping? (2) How often are steps aligned to the direction of the fall? (3) Do the prevalence and characteristics of steps associate with intrinsic and situational factors?

METHODS

We collected and analyzed video footage of 1516 falls experienced by 515 residents of LTC (of mean age 82.7 years). Using generalized estimating equations, we tested whether the prevalence, direction and size of steps associated with sex, age, fall direction, activity at the time of falling, cause of imbalance, and holding or grasping objects.

RESULTS

Stepping after imbalance was observed in 76% of falls, and 80% of these cases involved multiple steps. The direction of steps aligned with the initial fall direction in 81% of cases. The size of the first step was less than one-half foot length in 64% of cases. Secondary steps tended to be similar in size to the first step. Steps were more common for falls during walking than standing, and for sideways falls. Steps were less common in falls involving held objects, and steps were less likely to be aligned with the fall direction when reach-to-grasp responses were observed.

SIGNIFICANCE

Older adults in LTC tended to respond to falls with multiple compensatory steps. Steps were tailored to the direction of the fall, but small in size (less than one-half foot length in size). Exercise programs for fall prevention in older adults should focus on increasing step size to enhance the effectiveness of step recovery responses.

Daily Outdoor Cycling by Older Adults Preserves Reactive Balance Behavior: A Case-Control Study

We examined whether older adults who cycle outdoors regularly have better reactive balance control than noncycling older adults. Sixteen cyclist older adults and 24 age-, sex-, and health-matched controls who did not cycle (noncyclists) were exposed to unannounced perturbations of increased magnitudes in standing. We evaluated the strategies and kinematics employed at each perturbation magnitude. We found that cyclists exhibited a significantly higher stepping threshold, lower probability of stepping at each perturbation magnitude, and lower number of trials in which the participant needed to make a step to retain their balance. Cyclists also tended to recover balance using unloaded leg strategies in the first recovery step rather than a loaded leg strategy; they showed faster swing phase duration in the first recovery step, better controlling the displacement of center of mass than noncyclists. Older adults who cycle regularly outdoors preserve their reactive balance functions, which may reduce fall risks.

Differences in motor response to stability perturbations limit fall-resisting skill transfer

This study investigated transfer of improvements in stability recovery performance to novel perturbations. Thirty adults (20-53 yr) were assigned equally to three treadmill walking groups: groups exposed to eight trip perturbations of either low or high magnitude and a third control group that walked unperturbed. Following treadmill walking, participants were exposed to stability loss from a forward-inclined position (lean-and-release) and an overground trip. Lower limb joint kinematics for the swing phase of recovery steps was compared for the three tasks using statistical parametric mapping and recovery performance was analysed by margin of stability and base of support. The perturbation groups improved stability (greater margin of stability) over the eight gait perturbations. There was no group effect for stability recovery in lean-and-release. For the overground trip, both perturbation groups showed similar enhanced stability recovery (margin of stability and base of support) compared to controls. Differences in joint angle kinematics between treadmill-perturbation and lean-and-release were more prolonged and greater than between the two gait perturbation tasks. This study indicates that: (i) practising stability control enhances human resilience to novel perturbations; (ii) enhancement is not necessarily dependent on perturbation magnitude; (iii) differences in motor response patterns between tasks may limit transfer.

Accuracy and precision of simpler and lower-cost technologies to measure the initial lean angle, step length and step velocity for forward lean releases

Current technologies to measure the maximum forward lean angle, step length and velocity in a clinical setting are neither simple nor cheap. Therefore, the purpose of this study was to determine the accuracy and precision of four live and one post-processing measurement methods compared to the 3D motion analysis gold standard. Twelve healthy younger adults recovered balance, after being released from six randomly ordered forward initial lean angles, using four different live measurement methods: LabVIEW, load cell, inclinometer and protractor. The initial lean angle, step length and velocity were also calculated in post-processing using 2D video analysis and 3D motion analysis. The LabVIEW method was the most accurate and precise, followed by the protractor, inclinometer and load cell methods. The load cell method was the most complex, followed by the LabVIEW, inclinometer and protractor methods. The LabVIEW method was the most expensive, followed by the load cell, inclinometer and protractor methods. Video analysis was sufficiently accurate and precise, equal in complexity and much less expensive than the gold standard. Simpler and lower-cost technologies to measure the initial lean angle, step length and velocity are sufficiently accurate and precise (live: protractor, post-processing: video analysis) to potentially use in a clinical setting.

Reactive Balance Responses After Mild Traumatic Brain Injury: A Scoping Review

OBJECTIVE

Balance testing after concussion or mild traumatic brain injury (mTBI) can be useful in determining acute and chronic neuromuscular deficits that are unapparent from symptom scores or cognitive testing alone. Current assessments of balance do not comprehensively evaluate all 3 classes of balance: maintaining a posture; voluntary movement; and reactive postural response. Despite the utility of reactive postural responses in predicting fall risk in other balance-impaired populations, the effect of mTBI on reactive postural responses remains unclear. This review sought to (1) examine the extent and range of available research on reactive postural responses in people post-mTBI and (2) determine whether reactive postural responses (balance recovery) are affected by mTBI.

DESIGN

Scoping review.

METHODS

Studies were identified using MEDLINE, EMBASE, CINAHL, Cochrane Library, Dissertations and Theses Global, PsycINFO, SportDiscus, and Web of Science. Inclusion criteria were injury classified as mTBI with no confounding central or peripheral nervous system dysfunction beyond those stemming from the mTBI, quantitative measure of reactive postural response, and a discrete, externally driven perturbation was used to test reactive postural response.

RESULTS

A total of 4747 publications were identified, and a total of 3 studies (5 publications) were included in the review.

CONCLUSION

The limited number of studies available on this topic highlights the lack of investigation on reactive postural responses after mTBI. This review provides a new direction for balance assessments after mTBI and recommends incorporating all 3 classes of postural control in future research.

Near-Fall Detection in Unexpected Slips during Over-Ground Locomotion with Body-Worn Sensors among Older Adults

Slip-induced falls are a growing health concern for older adults, and near-fall events are associated with an increased risk of falling. To detect older adults at a high risk of slip-related falls, this study aimed to develop models for near-fall event detection based on accelerometry data collected by body-fixed sensors. Thirty-four healthy older adults who experienced 24 laboratory-induced slips were included. The slip outcomes were first identified as loss of balance (LOB) and no LOB (NLOB), and then the kinematic measures were compared between these two outcomes. Next, all the slip trials were split into a training set (90%) and a test set (10%) at sample level. The training set was used to train both machine learning models (n = 2) and deep learning models (n = 2), and the test set was used to evaluate the performance of each model. Our results indicated that the deep learning models showed higher accuracy for both LOB (>64%) and NLOB (>90%) classifications than the machine learning models. Among all the models, the Inception model showed the highest classification accuracy (87.5%) and the largest area under the receiver operating characteristic curve (AUC), indicating that the model is an effective method for near-fall (LOB) detection. Our approach can be helpful in identifying individuals at the risk of slip-related falls before they experience an actual fall.

Differences in muscle synergies among recovery responses limit inter-task generalisation of stability performance

Generalisation of adaptations is key to effective stability control facing variety of postural threats during daily life activity. However, in a previous study we could demonstrate that adaptations to stability control do not necessarily transfer to an untrained motor task. Here, we examined the dynamic stability and modular organisation of motor responses to different perturbations (i.e. unpredictable gait-trip perturbations and subsequent loss of anterior stability in a lean-and-release protocol) in a group of young and middle-aged adults (n = 57; age range 19-53 years) to detect potential neuromotor factors limiting transfer of adaptations within the stability control system. We hypothesized that the motor system uses different modular organisation in recovery responses to tripping and lean-and-release, which may explain lack in positive transfer of adaptations in stability control. After eight trip-perturbations participants increased their dynamic stability during the first recovery step (p < 0.001), yet they showed no significant improvement to the untrained lean-and-release transfer task compared to controls who did not undergo the perturbation exposure (p = 0.44). Regarding the neuromuscular control of responses, lower number of synergies (3 vs. 4) was found for the lean-and-release compared to the gait-trip perturbation task, revealing profound differences in both the timing and function of the recruited muscles to match the biomechanical specificity of different perturbations. Our results provide indirect evidence that the motor system uses different modular organisation in diverse perturbation responses, what possibly inhibits inter-task generalisation of adaptations in stability control.

Evaluating the contribution of reactive balance to prediction of fall rates cross-sectionally and longitudinally in persons with multiple sclerosis

BACKGROUND

Falls are common in persons with multiple sclerosis (PwMS). Reactive postural control-one's response to a balance perturbation-is likely an aspect of fall risk; however, the relationship between reactive posture and falls is poorly understood in PwMS.

OBJECTIVE

We evaluated tibialis anterior muscle onset latency (TA latency) after balance perturbations as a predictor of fall rates in PwMS, controlling for clinical, functional, sensory, psychological, and cognitive factors.

METHOD

At baseline of the 18-month cohort study, 122 participants with MS (EDSS = 2.23) were included. Assessments were conducted every 6 months.

RESULTS

Of the original 122 participants at the baseline collection, data were available from 41, 39, and 34 people at the 6, 12, and 18 month follow-ups, respectively. Percent fallers at the four time points were 35.3%, 12.2%, 15.4%, and 20.5%. Cross-sectionally (i.e., at baseline), the Timed Up-and-Go, Falls Efficacy Scale - International (FES-I), and TA latency after perturbations were significant predictors of retrospective falls rates using negative binomial regression. Longitudinally, random-effects negative binomial regression found that trait-level FES-I, Stroop Color-Word, and TA latency were significant predictors for falls rates.

CONCLUSION

Delays in automatic postural responses seem to account uniquely for fall rates in PwMS-beyond clinical, balance, or mobility measures. These delays may contribute to the increased fall rate in PwMS. In addition to brief self-report instruments (FES-I) and cognitive assessments, muscle onset after balance perturbations may be a valuable tool for predicting falls in those with MS.

Validity of the four-square step test in persons with haemophilia

INTRODUCTION

Recurrent bleeds into joints causes arthropathy leading to pain and reduced joint movement. This may cause a reduction in postural balance and increase the falls risk in patients with haemophilia (PWH). With an ageing PWH population the need to assess functional balance in clinic will be essential to monitor function and implement interventions to help maintain balance and prevent falls.

AIM

To assess the utility of the Four-Square Step Test (FSST) in PWH.

METHODS

80 PWH of all severity types were recruited and underwent a battery of outcome measures: FSST, Timed up & go (TUG), Short performance physical battery (SPPB), Haemophilia Activity List (HAL), ABC confidence questionnaire, and Haemophilia Joint Health score (HJHS). Demographics were collected, together with self-reported falls/trips history.

RESULTS

All 80 participants were able to complete all test measures. Median age 44.5 years. Number of participants reporting falls ranged from 23% in severe to 3% in mild. Recent trips 53% severe to 17% mild. Excellent Inter and intra-reliability, ICC of .981 (CI .953-.992), P < .001 and ICC .989 (.983-.993) P < .001, respectively. Strong correlations between FSST and TUG/ SPPB .753 and -.728, moderate correlation between FSST and ABC/HAL -.484, -.464 P < .01.

CONCLUSION

FSST is a valid and safe measure to use in PWH. It correlates strongly with other functional measures, has excellent inter and intra rater reliability. FSST correlates with age rather than severity type and provides information to the clinician on the speed/ability to change direction and clear an obstacle. ABC questionnaire was able to differentiate between severities and offers insight into patient confidence to move. SPPB had a ceiling effect with 52/80 scoring 12 and may not be suitable for PWH.

Comparison of the lower extremity kinematics and center of mass variations in sit-to-stand and stand-to-sit movements of non-faller and faller elderly

Objective

To compare the differences in sit-to-stand and stand-to-sit movements of older nonfalling males and older male fallers (also referred to herein as fallers) to contribute to the development of posture transfer–assisting devices or interventional therapies to prevent falls.

Design

Controlled study.

Setting

University research laboratory.

Participants

Ten older men (mean age, 75.9±5.4 years) who had fallen or been unstable at least once in the past year and 10 nonfalling older men (mean age, 70.0±5.0 years) participated in this study.

Interventions

Not applicable.

Main Outcome Measures

Movement duration; sagittal trunk, hip, knee, and ankle joint range of motion (ROM); anteroposterior and mediolateral (ML) center of mass (COM) total trajectory.

Results

During the sit-to-stand transition, fallers exhibited greater trunk joint ROM in the flexion and extension phase and smaller hip joint ROM in the extension phase as well as greater ML COM total trajectory. During stand-to-sit, older fallers exhibited greater trunk joint ROM in the flexion phase and smaller hip and knee joint ROM in the flexion phase as well as greater ML COM total trajectory. Older fallers took more time to perform the stand-to-sit and had greater ML COM total trajectory during the movement; additionally, they exhibited different proportional distributions of ROM for each joint compared with nonfaller.

Conclusion

Older fallers had more difficulty performing stand-to-sit than sit-to-stand; they exhibited more body sway in COM motion and, in particular, were unable to control ML motion y. Older fallers were more likely to adopt trunk, hip, and knee joint flexion strategies to maintain balance during sit-to-stand and stand-to-sit than nonfaller participants were.

Interadministrator Reliability of a Modified Instrumented Push and Release Test of Reactive Balance

CONTEXT

Traditional assessments of reactive balance require sophisticated instrumentation to ensure objective, highly repeatable paradigms. This instrumentation is clinically impractical. The Push and Release test (P&R) is a well-validated clinical test that examines reactive balance, and the application of wearable inertial measurement units (IMU) enables sensitive and objective assessment of this clinically feasible test. The P&R relies on administrator experience and may be susceptible to interadministration reliability concerns. The purpose of this study was to evaluate the interadministrator reliability of objective outcomes from an instrumented, modified version of the P&R test.

DESIGN

Crossover interadministrator design.

METHODS

Twenty healthy adults (20-35 y) completed the P&R in 4 directions with 2 different administrators. Measures quantified using IMUs included step latency, step length, and time to stability. Lean angle (LA) at release was used as a measure of administration consistency. The intraclass correlation coefficient (ICC) estimate was used to assess interadministrator reliability in each direction. To determine consistency of LA within and across administrators, we calculated the SDs for each rater by direction and the interadministrator reliability of LA using ICC.

RESULTS

Across individual directions, the ICC for agreement between raters ranged from .16 to .39 for step latency, from .52 to .62 for time to stability, and from .48 to .84 for step length. Summary metrics across all 4 directions produced higher ICC values. There was poor to moderate consistency in administration based on LA, but LA did not significantly affect any of the outcomes.

CONCLUSION

The modified P&R yields moderate interadministrator reliability and high validity. Summary metrics over all 4 directions (the maximum step latency, the median time to stability, and the median step length) are likely more reliable than direction-specific scores. Variations in body size should also be considered when comparing populations.

The Stepping Threshold Test for Reactive Balance: Validation of Two Observer-Based Evaluation Strategies to Assess Stepping Behavior in Fall-Prone Older Adults

Introduction: Measurement of reactive balance is critical for fall prevention but is severely underrepresented in the clinical setting due to the lack of valid assessments. The Stepping Threshold Test (STT) is a newly developed instrumented test for reactive balance on a movable platform, however, it has not yet been validated for fall-prone older adults. Furthermore, different schemes of observer-based evaluation seem possible. The aim of this study was to investigate validity with respect to fall risk, interpretability, and feasibility of the STT using two different evaluation strategies. Methods: This study involved 71 fall-prone older adults (aged ≥ 65) who underwent progressively increasing perturbations in four directions for the STT. Single and multiple-step thresholds for each perturbation direction were determined via two observer-based evaluation schemes, which are the 1) consideration of all steps (all-step-count evaluation, ACE) and 2) consideration of those steps that extend the base of support in the direction of perturbation (direction-sensitive evaluation, DSE). Established balance measures including global (Brief Balance Evaluations Systems Test, BriefBEST), proactive (Timed Up and Go, TUG), and static balance (8-level balance scale, 8LBS), as well as fear of falling (Short Falls Efficacy Scale-International, FES-I) and fall occurrence in the past year, served as reference measurements. Results: The sum scores of STT correlated moderately with the BriefBEST (ACE: r = 0.413; DSE: r = 0.388) and TUG (ACE: r = -0.379; DSE: r = -0.435) and low with the 8LBS (ACE: r = 0.173; DSE: r = 0.246) and Short FES-I (ACE: r = -0.108; DSE: r = -0.104). The sum scores did not distinguish between fallers and non-fallers. No floor/ceiling effects occurred for the STT sum score, but these effects occurred for specific STT thresholds for both ACE (mean floor effect = 13.04%, SD = 19.35%; mean ceiling effect = 4.29%, SD = 7.75%) and DSE (mean floor effect = 7.86%, SD = 15.23%; mean ceiling effect = 21.07%, SD = 26.08). No severe adverse events occurred. Discussion: Correlations between the STT and other balance tests were in the expected magnitude, indicating convergent validity. However, the STT could not distinguish between fallers and non-fallers, referring to a need for further studies and prospective surveys of falls to validate the STT. Current results did not allow a definitive judgment on the advantage of using ACE or DSE. Study results represented a step toward a reactive balance assessment application in a clinical setting.

The ability to increase the base of support and recover stability is limited in its generalisation for different balance perturbation tasks

Background

The assessment of stability recovery performance following perturbations contributes to the determination of fall resisting skills. This study investigated the association between stability recovery performances in two perturbation tasks (lean-and-release versus tripping).

Methods

Healthy adults (12 young: 24 ± 3 years; 21 middle-aged: 53 ± 5 years; 11 old: 72 ± 5 years) were suddenly released from a forward-inclined position attempting to recover stability with a single step. In a second task, all participants experienced a mechanically induced trip during treadmill walking. To assess dynamic stability performance, the antero-posterior margin of stability (MoS), the base of support (BoS), and the rate of increase in BoS were determined at each foot touchdown (TD) for both tasks.

Results

Only weak to moderate correlations in dynamic stability performance parameters were found between the two tasks (0.568 > r > 0.305, 0.001 < p < 0.04). A separation of participants according to the number of steps required to regain stability in the lean-and-release task revealed that multiple- (more than one step) compared to single-steppers showed a significantly lower MoS at TD (p = 0.003; g = 1.151), lower BoS at TD (p = 0.019; g = 0.888) and lower rate of increase in BoS until TD (p = 0.002; g = 1.212) after release. Despite these profound subgroup differences in the lean-and-release task, no differences between multiple- and single-steppers were observed in the stability recovery performance during tripping.

Conclusion

The results provide evidence that the ability to effectively control dynamic stability following a sudden balance disturbance in adults across a wide age range is limited in its generalisation for different perturbation tasks.

Perturbation practice in multiple sclerosis: Assessing generalization from support surface translations to tether-release tasks

OBJECTIVE

To determine whether improvements in protective stepping experienced after repeated support surface translations generalize to a different balance challenge in people with multiple sclerosis (PwMS) BACKGROUND: MS affects almost 1 million people in the United States and impairs balance and mobility. Perturbation practice can improve aspects of protective stepping in PwMS, but whether these improvements generalize is unknown.

METHODS

Fourteen PwMS completed two visits, 24hrs apart. The balance tasks included tether-release trials and support surface translations on a treadmill eliciting backward protective stepping. Margin of stability, step length, and step latency were calculated. Generalization was assessed via multilevel mediation models (MLMM) with bootstrapping to produce percentile and bias corrected confidence intervals RESULTS: There were no mediated effects for margin of stability or step latency; however, mediation was observed for step length, indicating that participants increased step length throughout the treadmill trials, and this generalized to tether-release trials DISCUSSION: MLMM may be useful for evaluating generalization of motor training to novel balance situations, particularly in small sample sizes. Using these analyses, we observed PwMS generalized improvements in step length, suggesting that aspects of protective step training may translate to improvements in other reactive balance tasks in PwMS.

The effects of the Otago Exercise Programme on actual and perceived balance in older adults: A meta-analysis

Objective

Falls are serious issues in older populations. Balance problems are a major cause of falls and may lead to fear of falling and decreased balance confidence. The Otago Exercise Programme (OEP) is an effective fall prevention program that benefits balance function and fear of falling. The primary aim of the meta-analysis was to investigate the effectiveness of the OEP intervention on actual balance performance (i.e., static, dynamic, proactive or reactive balance) and perceived balance ability (i.e., balance confidence or fear of falling) for older adults; the secondary aim was to examine which OEP protocol most improves balance in older adults.

Methods

A systematic electronic review search was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines to identify randomized controlled trials (RCTs) investigating the effects of the OEP on actual balance performance and perceived balance ability in healthy older adults, and examining which OEP training protocol and intervention format most improves balance.

Results

A total of 12 RCTs were included in the analyses. The OEP exerted significant effects on static balance (Hedges’s g = 0.388; 95% confidence interval [CI] = 0.131 to 0.645), dynamic balance (g = -0.228; 95% CI = -0.352 to -0.1.4), proactive balance (g = 0.239; 95% CI = 0.061 to 0.416) and perceived balance (g = -0.184; 95% CI = -0.320 to -0.048) in older adults. Subgroup analysis indicated that the group format for the OEP was more effective for improving static (p = 0.008), dynamic (p = 0.004) and perceived balance (p = 0.004) than was the individual format. Sessions of >30 minutes were more effective in improving static (p = 0.007) and perceived balance (p = 0.014) than were sessions of ≤30 minutes. However, the effects of the OEP on balance were unrelated to the types of control group, training frequency and training period.

Discussion

The OEP is helpful for improving actual balance including static, dynamic, and proactive balance; enhancing confidence in balance control; and reducing fear of falling in older adults. In particular, administrating the OEP in a group setting in >30-minute sessions may be the most appropriate and effective exercise protocol for improving balance.

Change in 'first-trial' performance after protective step practice in people with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a debilitating, neurodegenerative disorder causing considerable gait and balance dysfunction. Reactive balance (i.e., quick movements in response to a loss of balance) is particularly important for fall risk and is impaired in people with MS compared to neurotypical peers. Therefore, improving reactive balance among those with MS is critical. However, for maximum ecological validity, improvements in reactive balance through training would be demonstrable upon first loss-of-balance, rather than an average of several trials as is typically reported. This study evaluated changes in performance on the first stepping trial in people with MS after one day of practice.

METHODS

Fourteen people with MS underwent two, consecutive days of support-surface perturbations from stance. On day 1, participants underwent a single backward-stepping trial, followed by 35 practice trails (forward and backward). Approximately 24 h later, participants were again exposed to a single backward stepping perturbation. Protective stepping outcomes were step length, step latency, and margin of stability at first foot contact. The backward step performance on the first trial of days one and two were compared, and difference scores were evaluated for relationships with correlates based on theoretical considerations.

FINDINGS

First-trial margin of stability increased (improved) from day 1 to day 2 (P = .016). Steps were also faster on average by approximately 5 ms on day 2, although this improvement was not significant (P = .062).

INTERPRETATIONS

Although preliminary, these findings provide evidence that individuals with MS may be able to experience first-trial improvements after a low dose of perturbation training.

Adaptation of the Compensatory Stepping Response Following Predictable and Unpredictable Perturbation Training

Background

Effective training of the backward step response could be beneficial to improve postural stability and prevent falls. Unpredicted perturbation-based balance training (PBT), widely known as compensatory-step training, may enhance the fear of falling and the patterns of postural muscle co-contraction. Contrastingly, PBT with predictable direction or both direction and timing would suppress the fear and the co-contraction patterns during training, but the efficacy of predictable PBT for unpredictable perturbations is still unknown.

Objective

To compare the adaptation effects of compensatory-step training with and without predictable perturbations on backward stepping against unpredictable perturbations.

Methods

Thirty-three healthy young adults were randomly assigned to one of the following step training groups: Unpredicted, Predicted, and Self-initiated. In training sessions, participants were perturbed to induce a compensatory step with (Predicted group) or without (Unpredicted group) knowledge of the perturbation's direction or while knowing both the direction and timing of the perturbation (Self-initiated group). In test sessions (pre- and post-training), participants were instructed to recover their postural stability in response to an unpredicted perturbation. The margin of stability (MOS), center of mass (COM) shift, and step characteristics were measured during a backward step in both test and training sessions.

Results

All three groups showed a significant increase in the step length and velocity in the post-training sessions compared to those in the pre-training sessions. Moreover, in the Unpredicted and Predicted groups, but not in the Self-initiated group, the MOS at step contact was significantly increased following the training session. In addition, the Self-initiated group showed a significant increase in COM shift at 50 ms after slip onset during training compared to the Unpredicted and Predicted groups.

Conclusion

Unpredicted and predicted PBT improve step characteristics during backward stepping against unpredictable perturbations. Moreover, the unpredictable PBT and PBT with direction-predictable perturbations enhance the feedback postural control reflected as the postural stability at step contact.

Identifying and Characterizing Types of Balance Recovery Strategies Among Females and Males to Prevent Injuries in Free-Standing Public Transport Passengers

Free-standing passengers on public transport are subjected to perturbations during non-collision incidents caused by driver maneuvers, increasing the risk of injury. In the literature, the step strategy is described as a recovery strategy during severe perturbations. However, stepping strategies increase body displacement, ultimately subjecting passengers to higher risk of impacts and falls on public transport. This study investigates the influence of different recovery strategies on the outcome of balance recovery of free-standing public transport passengers, challenged in postural balance by the non-uniform vehicle dynamics. From high-speed video recordings, a qualitative investigation of the balance responses of volunteer participants in a laboratory experiment was provided. On a linearly moving platform, 24 healthy volunteers (11 females and 13 males) were subjected to perturbation profiles of different magnitude, shape and direction, mimicking the typical acceleration and deceleration behavior of a bus. A methodology categorizing the balancing reaction to an initial strategy and a recovery strategy, was used to qualitatively identify, characterize and, evaluate the different balance strategies. The effectiveness of different strategies was assessed with a grading criterion. Statistical analysis based on these ordinal data was provided. The results show that the current definition in the literature of the step strategy is too primitive to describe the different identified recovery strategies. In the volunteers with the most successful balancing outcome, a particularly effective balance recovery strategy not yet described in the literature was identified, labeled the fighting stance. High jerk perturbations seemed to induce faster and more successful balance recovery, mainly for those adopting the fighting stance, compared to the high acceleration and braking perturbation profiles. Compared to the pure step strategy, the characteristics of the fighting stance seem to increase the ability to withstand higher perturbations by increasing postural stability to limit body displacement.

Stability recovery performance in adults over a wide age range: A multicentre reliability analysis using different lean-and-release test protocols

The ability to effectively increase the base of support is crucial to prevent from falling due to stability disturbances and has been commonly assessed using the forward-directed lean-and-release test. With this multicentre study we examined whether the assessment of stability recovery performance using two different forward lean-and-release test protocols is reliable in adults over a wide age range. Ninety-seven healthy adults (age from 21 to 80 years) were randomly assigned to one out of two lean angle protocols: gradual increase to maximal forward-lean angle (maximal lean angle; n = 43; seven participants were excluded due to marker artefacts) or predefined lean angle (single lean angle; n = 26; 21 participants needed to be excluded due to multiple stepping after release or marker artefacts). Both protocols were repeated after 0.5 h and 48 h to investigate intra- and inter-session reliability. Stability recovery performance was examined using the margin of stability at release (MoS_RL) and touchdown (MoS_TD) and increase in base of support (BoS_TD). Intraclass correlation coefficients (confidence intervals at 95%) for the maximal lean angle and for the single lean angle were respectively 0.93 (0.89-0.96) and 0.94 (0.89-0.97) in MoS_RL, 0.85 (0.77-0.91) and 0.67 (0.48-0.82) in MoS_TD and 0.88 (0.81-0.93) and 0.80 (0.66-0.90) in BoS_TD, with equivalence being revealed for each parameter between all three measurements (p < 0.01). We concluded that the assessment of stability recovery performance parameters in adults over a wide age range with the means of the forward lean-and-release test is reliable, independent of the used lean angle protocol.

Pain Is Associated With Poor Balance in Community-Dwelling Older Adults: A Systematic Review and Meta-analysis

OBJECTIVES

Pain is a risk factor for falls in older adults, but the mechanisms are not well understood, limiting our ability to implement effective preventive strategies. The aim of this study was to systematically review and synthesize the literature that has examined the impact of pain on static, dynamic, multicomponent, and reactive balance in community-dwelling older adults.

DESIGN

Systematic review and meta-analysis.

SETTING AND PARTICIPANTS

Studies from inception to March 2019 were identified from electronic databases (MEDLINE, EMBASE, PsycINFO, CINAHL), contact with the primary authors, and reference lists of included articles.

METHODS

Cross-sectional and case-control studies that compared objective balance measures between older (minimum age 60 years) adults with and without pain were included.

RESULTS

Thirty-nine eligible studies (n = 17,626) were identified. All balance modalities (static, dynamic, multicomponent, and reactive) were significantly poorer in participants with pain compared to those without pain. Subgroup analyses revealed that chronic pain (pain persisting ≥3 months) impaired balance more than pain of unspecified duration. The effects of pain at specific sites (neck, lower back, hip, knee, and foot) on balance were not significantly different.

CONCLUSIONS AND IMPLICATIONS

Pain is associated with poor static, dynamic, multicomponent, and reactive balance in community-dwelling older adults. Pain in the neck, lower back, hip, knee, and foot all contribute to poor balance, and this is even more pronounced for chronic pain. Comprehensive balance and pain characteristic assessments may reveal mechanisms underlying the contribution of pain to instability and increased fall risk in older people.

Variations in situational risk factors for fractures of the distal forearm, hip, and vertebrae in older women

Background

Situational factors during a fall among three common types of fractures of the distal forearm, hip, and vertebrae among older women in Taiwan were investigated.

Methods

In 2016 ~ 2017, study participants were identified from those aged ≥65 years who visited emergency departments due to a fall in two university-affiliated hospitals in Taipei. In addition to individual characteristics, situational factors during the fall (location, activity, change of center of mass, fall mode, fall direction, initiating a protective response, and being hit) were collected. A sample of 203 distal-forearm fractures, 189 vertebral fractures, and 375 hip fractures was recruited, while 717 women with a soft-tissue injury were used as a control group. The identification of situational risk factors for each type of fracture was validated by using those who sustained one of the other two types of fracture as a control group.

Results

After adjusting for age and other individual characteristics, compared to soft-tissue injuries, distal-forearm fractures were significantly more likely to occur with slips (odds ratio [OR] = 11.0; 95% confidence interval [CI] = 4.76 ~ 25.4), trips (OR = 3.40; 95% CI = 1.42 ~ 8.17), step-downs (OR = 4.95; 95% CI = 2.15 ~ 11.4), and from sideways falls (OR = 1.73; 95% CI = 1.12 ~ 2.67) and significantly less likely to occur indoors (OR = 0.62; 95% CI = 0.42 ~ 0.90) or from backwards falls (OR = 0.62; 95% CI = 0.41 ~ 0.95). Hip fractures were significantly more likely to occur with step-downs (OR = 1.76; 95% CI = 1.13 ~ 2.75) and from backwards (OR = 3.16; 95% CI = 2.15 ~ 4.64) or sideways falls (OR = 5.56; 95% CI = 3.67 ~ 8.41) and significantly less likely when hitting an object (OR = 0.26; 95% CI = 0.13 ~ 0.52) or initiating a protective response (OR = 0.58; 95% CI = 0.36 ~ 0.93). Vertebral fractures were significantly more likely to occur with slips (OR = 2.42; 95% CI = 1.30 ~ 4.50), step-downs (OR = 2.53; 95% CI = 1.43 ~ 4.48), and backwards falls (OR = 2.15; 95% CI = 1.39 ~ 3.32). Similar results were found in the validation analyses.

Conclusions

Large variations in situational risk factors for the three types of fracture in older women existed. A combination of individual and situational risk factors may display a more-comprehensive risk profile for the three types of fracture, and an intervention that adds training programs on safe landing strategies and effective compensatory reactions may be valuable in preventing serious injuries due to a fall.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-021-02157-2.

Promoting Generalized Learning in Balance Recovery Interventions

Recent studies have shown balance recovery can be enhanced via task-specific training, referred to as perturbation-based balance training (PBT). These interventions rely on principles of motor learning where repeated exposure to task-relevant postural perturbations results in more effective compensatory balance responses. Evidence indicates that compensatory responses trained using PBT can be retained for many months and can lead to a reduction in falls in community-dwelling older adults. A notable shortcoming with PBT is that it does not transfer well to similar but contextually different scenarios (e.g., falling sideways versus a forward trip). Given that it is not feasible to train all conditions in which someone could fall, this limited transfer presents a conundrum; namely, how do we best use PBT to appropriately equip people to deal with the enormous variety of fall-inducing scenarios encountered in daily life? In this perspective article, we draw from fields of research that explore how general learning can be promoted. From this, we propose a series of methods, gleaned from parallel streams of research, to inform and hopefully optimize this emerging field where people receive training to specifically improve their balance reactions.

Stepping impairment and falls in older adults: A systematic review and meta-analysis of volitional and reactive step tests

OBJECTIVE

To systematically examine stepping performance as a risk factor for falls. More specifically, we examined (i) if step tests can distinguish fallers from non-fallers and (ii) the type of step test (e.g. volitional vs reactive stepping) that is required to distinguish fallers from non-fallers.

DATA SOURCE

PubMed, EMBASE, CINAHL, Cochrane Database of Systematic Reviews and reference lists of included articles.

STUDY SELECTION

Cross-sectional and cohort studies that assessed the association between at least one step test and falls in older people (age ≥ 60 and/or mean age of 65).

RESULTS

A meta-analysis of 61 studies (n = 9536) showed stepping performance was significantly worse in fallers compared to non-fallers (Cohen'sd 0.56, 95 % CI 0.48 to 0.64, p < 0.001, I² 66 %). This was the case for both volitional and reactive step tests. Twenty-three studies (n = 3615) were included in a diagnostic meta-analysis that showed that step tests have moderate sensitivity (0.70, 95 % CI 0.62 to 0.77), specificity (0.68, 95 % CI 0.58 to 0.77) and area under the receiver operating characteristics curve (AUC) (0.75, 95 % CI 0.59 to 0.86) in discriminating fallers from non-fallers.

CONCLUSIONS

This large systematic review demonstrated that both volitional and reactive stepping impairments are significant fall risk factors among older adults. Step tests can identify fallers from non-fallers with moderate accuracy.

Examining Different Motor Learning Paradigms for Improving Balance Recovery Abilities Among Older Adults, Random vs. Block Training-Study Protocol of a Randomized Non-inferiority Controlled Trial

Introduction: Falls are the leading cause of fatal and nonfatal injuries among older adults. Studies showed that older adults can reduce the risk of falls after participation in an unexpected perturbation-based balance training (PBBT), a relatively novel approach that challenged reactive balance control. This study aims to investigate the effect of the practice schedule (i.e., contextual interference) on reactive balance function and its transfer to proactive balance function (i.e., voluntary step execution test and Berg balance test). Our primary hypothesis is that improvements in reactive balance control following block PBBT will be not inferior to the improvements following random PBBT.

Methods and Analysis: This is a double-blind randomized controlled trial. Fifty community-dwelling older adults (over 70 years) will be recruited and randomly allocated to a random PBBT group (n = 25) or a block PBBT group (n = 25). The random PBBT group will receive eight training sessions over 4 weeks that include unexpected machine-induced perturbations of balance during hands-free treadmill walking. The block PBBT group will be trained by the same perturbation treadmill system, but only one direction will be trained in each training session, and the direction of the external perturbations will be announced. Both PBBT groups (random PBBT and block PBBT) will receive a similar perturbation intensity during training (which will be customized to participant’s abilities), the same training period, and the same concurrent cognitive tasks during training. The generalization and transfer of learning effects will be measured by assessing the reactive and proactive balance control during standing and walking before and after 1 month of PBBT, for example, step and multiple steps and fall thresholds, Berg balance test, and fear of falls. The dependent variable will be rank transformed prior to conducting the analysis of covariance (ANCOVA) to allow for nonparametric analysis.

Discussion: This research will explore which of the balance retraining paradigms is more effective to improve reactive balance and proactive balance control in older adults (random PBBT vs. block PBBT) over 1 month. The research will address key issues concerning balance retraining: older adults’ neuromotor capacities to optimize training responses and their applicability to real-life challenges.

Clinical Trial Registration: Helsinki research ethics approval has been received (Soroka Medical Center approval #0396-16-SOR; MOH_2018-07-22_003536; www.ClinicalTrials.gov, NCT04455607).

Volitional step execution is an ineffective predictor of recovery performance after sudden balance loss across the age range

Rapid stepping to preserve stability is a crucial action in avoiding a fall. It is also an important measure in the assessment of fall-resisting skills. We examined whether volitional step execution correlates with recovery stepping performance after sudden balance loss for adults of different ages. In addition, we investigated whether volitional step performance can discriminate between individuals with high and low balance recovery capabilities, i.e. between those making single versus multiple steps after balance perturbation. Healthy adults (28 young, 43 middle-aged and 26 older; 24 ± 4, 52 ± 5 and 72 ± 5 years respectively) performed a single step in the anterior direction volitionally in response to a mechanical stimulus to the heel. In a second stepping task, participants experienced sudden anterior balance loss in a lean-and-release protocol. For both tasks, an optical motion capture system was used to assess stepping kinematics. We found on average 28% shorter reaction times, 46% faster maximal step velocities and 48% higher rates of increase in base of support across all participants after sudden balance loss compared to volitional stepping (p < 0.001). There was a significant age-related decline in recovery stepping performance after sudden balance loss: 24/26 older, 15/43 middle-aged and none of the younger adults required two or more steps to regain balance (p < 0.001). Multiple- compared to single-steppers had on average 23% shorter step lengths and 12% lower maximal step velocities for the lean-and-release task (p < 0.01). Multiple-steppers also had reduced rates of increase in base of support for both stepping tasks (14% for balance recovery and 11% for volitional stepping). Furthermore, in examining the relationship between the results of the two tasks, only weak to moderate correlations were observed for step velocity and rate of increase in base of support (0.36 ≤ r ≤ 0.52; p < 0.001). Thus, performance in volitional step execution has a low potential to explain variability in recovery response after sudden balance loss in adults across the lifespan and hence seems less suitable to be used to identify deficiencies in reactive stepping responses necessary to cope with sudden balance disturbances.

Comparison of forward and backward postural perturbations in mild-to-moderate Parkinson's disease

BACKGROUND

Assessing postural stability in Parkinson's disease (PD) often relies on measuring the stepping response to an imposed postural perturbation. The standard clinical technique relies on a brisk backwards pull at the shoulders by the examiner and judgement by a trained rater. In research settings, various quantitative measures and perturbation directions have been tested, but it is unclear which metrics and perturbation direction differ most between people with PD and controls.

OBJECTIVES

(1) Use standardized forward vs. backward perturbations of a support surface to evaluate reactive stepping performance between PD and control participants. (2) Evaluate the utility of using principal components analysis to capture the dynamics of the reactive response and differences between groups.

METHODS

Sixty-two individuals participated (40 mild-to-moderate PD, off medication). Standardized rapid translations of the support surface were applied, requiring at least one step, backward or forward, to restore balance. The number of steps taken and the projection of the first principal component (PC1) of the center of pressure (COP) time series were entered in linear repeated-measures mixed effect models.

RESULTS

Forward falls required significantly fewer steps to recover than backward falls. PC1 captured more than half of the variance in the COP trajectory. Analysis of the PC1 projection revealed a significant interaction effect of group (PD vs. controls) by direction, such that there was a group difference in forward stepping, but not backward.

SIGNIFICANCE

Forward reactive stepping in PD differed from controls more than backward-stepping. PC1 projections of the COP trajectory capture the dynamics of the postural response and differ between PD and controls.

The Effects of Bicycle Simulator Training on Anticipatory and Compensatory Postural Control in Older Adults: Study Protocol for a Single-Blind Randomized Controlled Trial

Background: Falls are the leading cause of fatal and non-fatal injuries among older adults. Perturbation-Based-Balance Training (PBBT) is a promising approach to reduce fall rates by improving reactive balance responses. PBBT programs are designed for older adults who are able to stand and walk on a motorized treadmill independently. However, frail older adults, whose fall rates are higher, may not have this ability and they cannot participate. Thus, there is a critical need for innovative perturbation exercise programs to improve reactive balance and reduce the fall risks among older adults in a wider range of functioning. Trunk and arms are highly involved in reactive balance reactions. We aim to investigate whether an alternative PBBT program that provides perturbations during hands-free bicycling in a sitting position, geared to improve trunk and arm reactive responses, can be transferred to reduce fall risks and improve balance function among pre-frail older adults.

Methods: In a single-blinded randomized-controlled trial, 68 community-dwelling pre-frail older adults are randomly allocated into two intervention groups. The experimental group receives 24-PBBT sessions over 12-weeks that include self-induced internal and machine-induced external unannounced perturbations of balance during hands-free pedaling on a bicycle-simulator system, in combination with cognitive dual-tasks. The control group receives 24 pedaling sessions over 12-weeks by the same bicycle-simulator system under the same cognitive dual-tasks, but without balance perturbations. Participants' reactive and proactive balance functions and gait function are assessed before and after the 12-week intervention period (e.g., balance reactive responses and strategies, voluntary step execution test, postural stability in upright standing, Berg Balance Test, Six-meter walk test, as well as late life function and fear of falling questionnaires).

Discussion: This research addresses two key issues in relation to balance re-training: (1) generalization of balance skills acquired through exposure to postural perturbations in a sitting position investigating the ability of pre-frail older adults to improve reactive and proactive balance responses in standing and walking, and (2) the individualization of perturbation training to older adults' neuromotor capacities in order to optimize training responses and their applicability to real-life challenges.

Clinical Trial Registration:www.clinicaltrials.gov, NCT03636672 / BARZI0104; Registered: July 22, 2018; Enrolment of the first participant March: 1, 2019. See Supplementary File.

Use of the extended feasible stability region for assessing stability of perturbed walking

Walking stability has been assessed through gait variability or existing biomechanical measures. However, such measures are unable to quantify the instantaneous risk of loss-of-balance as a function of gait parameters, body sway, and physiological and perturbation conditions. This study aimed to introduce and evaluate novel biomechanical measures for loss-of-balance under various perturbed walking conditions. We introduced the concept of ‘Extended Feasible Stability Region (ExFSR)’ that characterizes walking stability for the duration of an entire step. We proposed novel stability measures based on the proximity of the body’s centre of mass (COM) position and velocity to the ExFSR limits. We quantified perturbed walking of fifteen non-disabled individuals and three individuals with a disability, and calculated our proposed ExFSR-based measures. 17.2% (32.5%) and 26.3% (34.0%) of the measured trajectories of the COM position and velocity during low (high) perturbations went outside the ExFSR limits, for non-disabled and disabled individuals, respectively. Besides, our proposed measures significantly correlated with measures previously suggested in the literature to assess gait stability, indicating a similar trend in gait stability revealed by them. The ExFSR-based measures facilitate our understanding on the biomechanical mechanisms of loss-of-balance and can contribute to the development of strategies for balance assessment.

Evaluating Balance Recovery Techniques for Users Wearing Head-Mounted Display in VR

Room-scale 3D position tracking enables users to explore a virtual environment by physically walking, which improves comfort and the level of immersion. However, when users walk with their eyesight blocked by a head-mounted display, they may unexpectedly lose their balance and fall if they bump into real-world obstacles or unintentionally shift their center of mass outside the margin of stability. This paper evaluates balance recovery methods and intervention timing during the use of VR with the assumption that the onset of a fall is given. Our experiment followed the tether-release protocol during clinical research and induced a fall while a subject was engaged in a secondary 3D object selection task. The experiment employed a two-by-two design that evaluated two assistive techniques, i.e., video-see-through and auditory warning at two different timings, i.e., at fall onset and 500ms prior to fall onset. The data from 17 subjects showed that video-see-through triggered 500 ms before the onset of fall can effectively help users recover from falls. Surprisingly, video-see-through at fall onset has a significant negative impact on balance recovery and produces similar results to those of the baseline condition (no intervention).

Interactions between initial posture and task-level goal explain experimental variability in postural responses to perturbations of standing balance

Postural responses to similar perturbations of standing balance vary widely within and across subjects. Here, we identified two sources of variability and their interactions by combining experimental observations with computational modeling: differences in posture at perturbation onset across trials and differences in task-level goals across subjects. We first collected postural responses to unpredictable backward support-surface translations during standing in 10 young adults. We found that maximal trunk lean in postural responses to backward translations were highly variable both within subjects (mean of ranges = 28.3°) and across subjects (range of means = 39.9°). Initial center of mass (COM) position was correlated with maximal trunk lean during the response, but this relation was subject specific (R² = 0.29-0.82). We then used predictive simulations to assess causal relations and interactions with task-level goal. Our simulations showed that initial posture explains the experimentally observed intrasubject variability with a more anterior initial COM position increasing the use of the hip strategy. Differences in task-level goal explain observed intersubject variability with prioritizing effort minimization leading to ankle strategies and prioritizing stability leading to hip strategies. Interactions between initial posture and task-level goal explain observed differences in intrasubject variability across subjects. Our findings suggest that variability in initial posture due to increased sway as observed in older adults might increase the occurrence of less stable postural responses to perturbations. Insight in factors causing movement variability will advance our ability to study the origin of differences between groups and conditions.NEW & NOTEWORTHY Responses to perturbations of standing balance vary both within and between individuals. By combining experimental observations with computational modeling, we identified causes of observed kinematic variability in healthy young adults. First, we found that trial-by-trial differences in posture at perturbation onset explain most of the kinematic variability observed within subjects. Second, we found that differences in prioritizing effort versus stability explained differences in the postural response as well as differences in trial-by-trial variability across subjects.

Posterior single-stepping thresholds are prospectively related to falls in older women

BACKGROUND

Falls are a leading cause of injury in older women. Stepping thresholds quantify balance-reaction capabilities. It is unclear how such evaluations predict falls in comparison to, or as a complement to, other objective measures of gait, standing postural control, strength, and balance confidence.

AIMS

The objective of this study was to determine if stepping thresholds are prospectively related to falls in older women.

METHODS

For this prospective cohort study, 125 ambulatory, community-dwelling women, age ≥ 65 years were recruited. Using a treadmill to deliver perturbations to standing participants, we determined anteroposterior single- and multiple-stepping thresholds. Here, thresholds represent the minimum perturbation magnitudes that consistently evoke one step or multiple steps. In addition, gait kinematics, obstacle-crossing kinematics, standing sway measures, unipedal stance time, the functional reach, lower extremity isometric strength, grip strength, balance confidence, and fall history were evaluated. Falls were prospectively recorded for one year.

RESULTS

Seventy-four participants (59%) fell at least once. Posterior single-stepping thresholds were the only outcome that predicted future fall status (OR = 1.50, 95% CI 1.01-2.28; AUC = .62). A multivariate approach added postural sway with eyes closed as a second predictive variable, although predictive abilities were not meaningfully improved.

DISCUSSION

These results align with the previous evidence that reactive balance is a prospective indicator of fall risk. Unlike previous studies, strength scaled to body size did not contribute to fall prediction.

CONCLUSION

Posterior single-stepping thresholds held a significant relationship with future fall status. This relationship was independent of, and superior to that of, other measures of standing balance, gait, strength, and balance confidence.

Impact of pain on reactive balance and falls in community-dwelling older adults: a prospective cohort study

BACKGROUND

pain is associated with increased postural sway and falls in older adults. However, the impact of pain on reactive balance induced by postural perturbations and how this might predispose older adults to falls is not known.

OBJECTIVE

to investigate whether any pain, back/neck pain and lower limb pain are associated with poor reactive balance and prospective fall outcomes in older adults.

DESIGN

12-month prospective cohort study.

SETTING

community.

SUBJECTS

242 community-dwelling older adults aged 70+ years.

METHODS

participants completed a questionnaire on the presence of pain and underwent force-controlled waist-pull postural perturbations while standing. Force thresholds for stepping, step initiation time, step velocity and step length were quantified. Falls were monitored with monthly falls calendars for 12-months.

RESULTS

participants with lower limb pain had significantly lower force thresholds for stepping. Those with any pain or pain in the back/neck had longer step initiation time, slower step velocity and shorter step length. The three pain measures (any pain, back/neck pain, lower limb pain) were significantly associated with multiple falls when adjusted for age, sex, body mass index, use of polypharmacy, strength and walking speed. In mediation analyses, there was a significant indirect effect of reactive balance for the relationship between back/neck pain and falls with fractures.

CONCLUSIONS

older people with pain have impaired reactive balance and an increased risk of falls. Reactive balance partially mediated the association between pain and fall-related fractures. Further research is required to confirm the findings of this study.

Ankle motor strategy use in older and younger adults as assessed by a two-dimensional kinematic analysis smart device application

Background/aims

Motor strategies change with age, resulting in balance deficits. Clinical options for objectively measuring motor strategies are limited. The use of two-dimensional kinematic analysis through smart devices and applications may provide a cost-effective portable solution for measuring differences in motor strategy use between older and younger adults. The aims of this study were to investigate the concurrent validity of a two-dimensional software and two-dimensional application and to determine whether the application could capture the difference in ankle motor strategy use by older and younger adults (construct validity).

Methods

Video clips captured by Sony and iPad Air cameras were used to assess concurrent validity between the two-dimensional software and application. A total of 30 older (72.6 ± 4.0 years) and 30 younger (26.5±4.5 years) adults performed forward and backward stepping. A two-dimensional applicationmeasured the ankle position in degrees and time taken in seconds to initiate and complete a compensatory step.

Results

The two-dimensional software and app demonstrated excellent reliability (ICC2,1 ≥0.994). The ankle forward stop angle differed significantly between older and younger adults (P=0.012). No differences were observed in time taken to initiate and complete a compensatory step.

Conclusions

The two-dimensional application appears to be a valid alternative to two-dimensional software for measuring ankle motor strategies. Further investigation for clinical use is warranted.

The kinematics and strategies of recovery steps during lateral losses of balance in standing at different perturbation magnitudes in older adults with varying history of falls

BACKGROUND

Step-recovery responses are critical in preventing falls when balance is lost unexpectedly. We investigated the kinematics and strategies of balance recovery in older adults with a varying history of falls.

METHODS

In a laboratory study, 51 non-fallers (NFs), 20 one-time fallers (OFs), and 12 recurrent-fallers (RFs) were exposed to random right/left unannounced underfoot perturbations in standing of increasing magnitude. The stepping strategies and kinematics across an increasing magnitude of perturbations and the single- and multiple-step threshold trials, i.e., the lowest perturbation magnitude to evoke single step and multiple steps, respectively, were analyzed. Fall efficacy (FES) and self-reported lower-extremity function were also assessed.

RESULTS

OFs had significantly lower single- and multiple-step threshold levels than NFs; the recovery-step kinematics were similar. Surprisingly, RFs did not differ from NFs in either threshold. The kinematics in the single-step threshold trial in RFs, however, showed a significant delay in step initiation duration, longer step duration, and larger center of mass (CoM) displacement compared with NFs and OFs. In the multiple-step threshold trial, the RFs exhibited larger CoM displacements and longer time to fully recover from balance loss. Interestingly, in the single-stepping trials, 45% of the step-recovery strategies used by RFs were the loaded-leg strategy, about two times more than OFs and NFs (22.5 and 24.2%, respectively). During the multiple-stepping trials, 27.3% of the first-step recovery strategies used by RFs were the loaded-leg strategy about two times more than OFs and NFs (11.9 and 16.4%, respectively), the crossover stepping strategy was the dominated response in all 3 groups (about 50%). In addition, RFs reported a lower low-extremity function compared with NFs, and higher FES in the OFs.

CONCLUSIONS

RFs had impaired kinematics during both single-step and multiple-step recovery responses which was associated with greater leg dysfunction. OFs and NFs had similar recovery-step kinematics, but OFs were more likely to step at lower perturbation magnitudes suggesting a more "responsive" over-reactive step response related from their higher fear of falling and not due to impaired balance abilities. These data provide insight into how a varying history of falls might affect balance recovery to a lateral postural perturbation.

TRIAL REGISTRATION

This study was registered prospectively on November 9th, 2011 at clinicaltrials.gov ( NCT01439451 ).

Exercise of Dynamic Stability in the Presence of Perturbations Elicit Fast Improvements of Simulated Fall Recovery and Strength in Older Adults: A Randomized Controlled Trial

Age-related impairments of reactive motor responses to postural threats and reduced muscular capacities of the legs are key factors for the higher risk of falling in older people. It has been evidenced that a training of dynamic stability in the presence of perturbations has the potential to improve these deficits. However, the time course of training effects during such interventions is poorly understood. The purpose of this parallel-group study was to investigate the temporal adaptation dynamics of the balance recovery performance and leg strength during a dynamic stability training. Forty-two healthy older adults (65–85 years) were randomly assigned to a training (n = 27, analyzed n = 18) or control group (n = 15, n = 14). The training was conducted in a group setting for 6 weeks (3×/week, 45 min). The exercises focused on the mechanism of stability control (i.e., modulation of the base of support and segment counter-rotations around the center of mass) during standing, stepping, and jumping on unstable surfaces with a high balance intensity. Before, after 3 and after 6 weeks, the maximum plantar flexion moment and the knee extension moment were assessed. The recovery performance was evaluated by a simulated forward fall (lean-and-release test) and the margin of stability concept. The margin of stability at release decreased significantly after 3 weeks of training (34%, effect size g = 0.79), which indicates fast improvements of balance recovery performance. The margin of stability further decreased after week 6 (53%, g = 1.21), yet the difference between weeks 3 and 6 was not significant. Furthermore, the training led to significant increases in the plantar flexion moment after weeks 3 (12%, g = 0.72) and 6 (13%, g = 0.75) with no significant difference between weeks. For the knee extension moment, a significant increase was found only after week 6 (11%, g = 1.07). The control group did not show any significant changes. This study provides evidence that a challenging training of dynamic stability in the presence of perturbations can improve balance recovery performance and leg strength of older adults already after a few weeks. Therefore, short-term training interventions using this paradigm may be an effective strategy for fall prevention in the elderly population, particularly when intervention time is limited.

Quality of life in elderly people after a hip fracture: a prospective study

BACKGROUND

Hip fracture is an important social and medical problem due to its increasing prevalence, the consequences for health and the economic impact on the health care system, but there is no doubt that it also has repercussions on health-related quality of life (HRQoL). Hence the importance of understanding and determining the impact of the condition on everyday life from the perspective of the patient's physical, emotional and social well-being.

PURPOSE

To determine the impact of hip fracture on HRQoL of people over the age of 65 1 month after surgery, related factors and the effects on functional ability and mood.

METHODS

Prospective observational study conducted in the traumatology units of two university hospitals in the province of Cáceres with consecutive sampling of all patients over the age of 65 admitted for hip fracture surgery during the study period. Sociodemographic and clinical data were recorded at the time of admission and prospectively at the follow-up visit 1 month later. Clinical, social, quality of life (EQ-5D-), basic functional and instrumental capacity (Barthel Index (BI) and Lawton & Brody Scale), and geriatric depression (Yesavage) variables were collected.

RESULTS

The study included 224 patients with a median age of 84.6 years (SD ± 6.1), 76.3% were female. Charlson's comorbidity was 5.3 (SD ± 1.2). The EQ-5D index decreased from 0.62 (SD ± 0.35) to 0.16 at 1 month follow up (SD ± 0.20) p <  0.001. The mean Visual Analog Scale (VAS) score of EQ-5D decreased from 72.8 (SD ±15.8) to 48.3 (SD ± 17.2) p <  0.001. All dimensions of EQ-5D showed a significant reduction from the time of pre-fracture status to 1 month after surgery. Independent factors associated with HRQoL 1 month after surgery were pre-fracture status Barthel Index score, Lawton and Brody scale, presence of depression, and type of surgery.

CONCLUSIONS

After a hip fracture, patients experience considerable deterioration in their HRQoL, especially in self-care, daily activities, and mobility. There is also a significant decline in functional capacity for both the basic and instrumental activities of daily living. One month after surgery, HRQoL is a long way from pre-fracture levels.

Development of a fall-risk assessment profile for community-dwelling older adults by using the National Health Interview Survey in Taiwan

Background

Falls represent a global health issue among older adults and cause a considerable burden on medical systems. In this study, a fall-risk assessment profile was developed for community-dwelling older adults.

Method

The data of survey participants aged > 65 years were obtained from three rounds (2005, 2009, and 2013) of the National Health Interview Survey in Taiwan. In total, 8356 older participants were included in this study. Logistic regression analyses were used to determine potential predictors associated with falls. The regression coefficients of the predictors in the final model were translated into scores (by multiplying by 5) and then summed to obtain a total risk-score for falls. A receiver operating characteristic (ROC) curve was used to evaluate the discriminative performance of the risk assessment profile.

Result

Self-reported falls within 1 year accounted for 19.1% of the total falls. The predictors that were included in the risk profile according to the logistic regression analysis results were as follows: female sex (adjusted odds ratio = 1.57; risk-score = 2), living alone (adjusted odds ratio = 1.56; risk-score = 2), urinary incontinence (adjusted odds ratio = 1.36; risk-score = 2), perceived unhealthiness (adjusted odds ratio = 1.32; risk-score = 1), perceived pain (adjusted odds ratio = 1.51; risk-score = 2), hospital admission in the past year (adjusted odds ratio = 2.42; risk-score = 4), low activity of daily living (ADL) scores (adjusted odds ratio = 1.29; risk-score = 1), and low mobility function scores (adjusted odds ratio = 1.68; risk-score = 3). At a total risk-score cutoff point of 6 (range 0–17), the model predicted falls with a sensitivity and specificity of 75.16 and 52.75%, respectively (area under the ROC curve = 0.70).

Conclusion

The fall-risk assessment profile comprising eight predictors—female sex, living alone, incontinence, perceived unhealthiness, perceived pain, hospital admission in the past year, low ADL scores, and low mobility function scores—may serve as an assessment tool for identification of older adults with a high risk of falling, and assessment results can be used to facilitate community-based intervention.

Effects of Exergaming on Balance of Healthy Older Adults: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Balance is critical for older adults to perform daily activities. However, age-related declines in balance increase the risk of falls and severe injuries, such as bone fractures and head injuries. Exergames have been widely applied to improve health-related outcomes in older adults. This meta-analysis aims to quantify the effects of exergaming interventions on balance performance in healthy older adults. A literature search was performed using PubMed, ScienceDirect, SPORTDiscus, COCHRANE, EBSCO, and EMBASE. A total of 16 experimental studies met inclusion criteria for a full-text review. Data synthesis examined balance functions, including static, dynamic, proactive, and perceived balance abilities when performing daily activities. Intervention protocols of the reviewed studies included an average of two to three 40-minute exergaming sessions per week for 8 weeks. A random effects model identified significant effects in favor of the exergaming group, with moderate effect size in dynamic balance (Hedges' g = 0.36, 95% CI = 0.26-1.30, P < 0.001), and perceived balance (Hedges' g = 0.31, 95% CI = 0.04-0.58, P = 0.02); and considerable effect size in Chair Stand Test (Hedges' g = 0.78, 95% CI = 0.26-1.30, P = 0.003), and balance test batteries (Hedges' g = 0.72, 95% CI = 0.42-1.02, P < 0.001). No significant effect was found in the static balance (Hedges' g = 0.22, 95% CI = -0.31 to 0.76, P = 0.42), or proactive balance (Hedges' g = 0.54, 95% CI = -0.12 to 1.20, P = 0.11). Meta-analysis identified exergaming-associated benefits in older adults' balance function and confidence. This finding supports the feasibility of exergaming as a supplementary approach to improve balance for healthy older adults. Health professionals may optimize treatment effect by integrating exergaming sessions into a traditional balance exercise program.

Reactive gait and postural adjustments following the first exposures to (un)expected stepdown

This study evaluated the reactive biomechanical strategies associated with both upper- and lower-body (lead and trail limbs) following the first exposures to (un)expected stepdown at comfortable (1.22 ± 0.08 m/s) and fast (1.71 ± 0.11 m/s) walking velocities. Eleven healthy adults completed 34 trails per walking velocity over an 8-m, custom-built track with two forceplates embedded in its center. For the expected stepdown, the track was lowered by 0-, -10- and -20-cm from the site of the second forceplate, whereas the unexpected stepdown was created by camouflaging the second forceplate (-10-cm). Two-way repeated-measurement ANOVAs detected no velocity-related effects of stepdown on kinematic and kinetic parameters during lead limb stance-phase, and on the trail limb stepping kinematics. However, analyses of significant interactions revealed greater peak flexion angles across the trunk and the trail limb joints (hip, knee and ankle) in unexpected versus expected stepdown conditions at a faster walking velocity. The -10-cm unexpected stepdown (main effect) had a greater influence on locomotor behavior compared to expected conditions due mainly to the absence of predictive adjustments, reflected by a significant decrease in peak knee flexion, contact time and vertical impulse during stance-phase. Walking faster (main effect) was associated with an increase in hip peak flexion and net anteroposterior impulse, and a decrease in contact time and vertical impulse during stepdown. The trail limb, in response, swung forward faster, generating a larger and faster recovery step. However, such reactive stepping following unexpected stepdown was yet a sparse compensation for an unstable body configuration, assessed by significantly smaller step width and anteroposterior margin-of-stability at foot-contact in the first-recovery-step compared with expected conditions. These findings depict the impact of the expectedness of stepdown onset on modulation of global dynamic postural control for a successful accommodation of (un)expected surface elevation changes in young, healthy adults.