Stressing the postural response. A quantitative method for testing balance

Mobile Data Gathering and Preliminary Analysis for the Functional Reach Test

The functional reach test (FRT) is a clinical tool used to evaluate dynamic balance and fall risk in older adults and those with certain neurological diseases. It provides crucial information for developing rehabilitation programs to improve balance and reduce fall risk. This paper aims to describe a new tool to gather and analyze the data from inertial sensors to allow automation and increased reliability in the future by removing practitioner bias and facilitating the FRT procedure. A new tool for gathering and analyzing data from inertial sensors has been developed to remove practitioner bias and streamline the FRT procedure. The study involved 54 senior citizens using smartphones with sensors to execute FRT. The methods included using a mobile app to gather data, using sensor-fusion algorithms like the Madgwick algorithm to estimate orientation, and attempting to estimate location by twice integrating accelerometer data. However, accurate position estimation was difficult, highlighting the need for more research and development. The study highlights the benefits and drawbacks of automated balance assessment testing with mobile device sensors, highlighting the potential of technology to enhance conventional health evaluations.

Measuring the Reliability of Postural Sway Measurements for a Static Standing Task: The Effect of Age

Background: A force plate is used to determine the ability to balance ability. However, only some medical centers or laboratories are equipped with force plates because they are costly so a low-cost force plate is required for home care or health care institutes. Few studies compare the reliability of postural sway measurements in terms of age. This study proposes a low-cost force plate to select reliable parameters to evaluate postural sway.

Objectives: To determine the intra-rater reliability of a novel force plate and the effect of age difference on the intra-rater test-retest reliability for the center of pressure (COP).

Methods: Forty participants were enrolled for this study: 20 youths and 20 older adults. Participants stood on a custom-made and low-cost force plate with eyes opened and eyes closed to measure COP-related parameters. The within-day test-retest reliability was measured at two sessions on the same day and the between-days reliability was measured on two different days. The COP-related parameters include the average velocity of COP, the average velocity in the antero-posterior and medio-lateral directions, the mean distance of COP and the mean distance in the antero-posterior and medio-lateral directions. An intra-class correlation coefficient test with one-way random model was performed to determine the reliability of different variables within-days and between-days. The results were presented in single measurement of intraclass correlation coefficient (ICC), the standard error of measurements, and the minimal detectable changes of each COP-related parameters.

Results: The novel low-cost force plate demonstrates excellent reliability in terms of the COP velocity related parameters for within- and between-day measurements. The ICC of COP distance related parameters were good to excellent reliability for between-day measurements (range: 0.43–0.84). Older adults demonstrated excellent reliability in terms of the mean distance for antero-posterior and the results were better than those for younger participants for the eyes-opened and eyes-closed conditions. The reliability in terms of the mean distance for medio-lateral was poor to good for older adults (range: 0.38–0.55), and excellent for younger participants.

Conclusion: The novel and low-cost force plate reliably measured balance and age affects the reliability of different COP variables, so the results of this study were pertinent to the selection of COP measures.

The measurement properties of the Lean-and-Release test in people with incomplete spinal cord injury or disease

OBJECTIVE

To evaluate test-retest reliability, agreement, and convergent validity of the Lean-and-Release test for the assessment of reactive stepping among individuals with incomplete spinal cord injury or disease (iSCI/D).

DESIGN

Multi-center cross-sectional multiple test design.

SETTING

SCI/D rehabilitation hospital and biomechanics laboratory.

PARTICIPANTS

Individuals with motor incomplete SCI/D (iSCI/D).

INTERVENTIONS

None.

OUTCOME MEASURES

Twenty-six participants attended two sessions to complete the Lean-and-Release test and a battery of clinical tests. Behavioral (i.e. one-step, multi-step, loss of balance) and temporal (i.e. timing of foot off, foot contact, swing of reactive step) parameters were measured. Test-retest reliability was determined with intraclass correlation coefficients, and agreement was evaluated with Bland-Altman plots. Convergent validity was assessed through correlations with clinical tests.

RESULTS

The behavioral responses were reliable for the Lean-and-Release test (ICC = 0.76), but foot contact was the only reliable temporal parameter using data from a single site (ICC = 0.79). All variables showed agreement according to the Bland-Altman plots. The behavioral responses correlated with scores of lower extremity strength (0.54, P<0.01) and balance confidence (0.55, P < 0.01). Swing time of reactive stepping correlated with step time (0.73, P < 0.01) and cadence (-0.73 P < 0.01) of over ground walking.

CONCLUSIONS

The behavioral response of the Lean-and-Release test is a reliable and valid measure for people with iSCI/D. Our findings support the use of the behavioral responses to evaluate reactive stepping for research and clinical purposes.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02960178.

SC, Crews RT. Diabetes and Reactive Balance: Quantifying Stepping Thresholds With a Simple Spring Scale to Measure Fall-Risk in Ambulatory Older Adults

BACKGROUND

Fall-risk assessments for patients with diabetes fail to consider reactive responses to balance loss. The purpose of this study was to assess the feasibility of using a simple clinical tool to evaluate the impact of diabetes and fall history on reactive balance in older adults.

METHODS

We recruited 72 older adults with and without diabetes. Postural perturbations were applied by a waist-mounted spring scale. Stepping thresholds (STs) in the anterior and posterior directions were defined as the lowest spring-loads that induced a step. Balance was assessed via the National Institutes of Health Toolbox Standing Balance Test, and lower extremity sensation was assessed using vibratory perception threshold and Semmes-Weinstein monofilaments. Fall history over the past year was self-reported. Cox regressions and analysis of variance were used to compare hazard rates for stepping and observed STs between groups.

RESULTS

Anterior STs were elicited in 42 subjects and posterior STs in 65 subjects. Hazard rates for posterior ST were significantly affected by diabetes, with greater hazards for fallers with diabetes versus control fallers and nonfallers, after accounting for balance and sensory loss. For those who stepped, ST was lower in the posterior direction for the diabetes group. Additionally, anterior but not posterior ST was lower in all fallers vs all nonfallers.

CONCLUSIONS

The waist-mounted spring scale is a clinically implementable device that can assess ST in older adults with diabetes. Using the device, we demonstrated that ST was affected by diabetes and could potentially serve as a fall-risk factor independent of balance or sensory loss.

Cortical Engagement Metrics During Reactive Balance Are Associated With Distinct Aspects of Balance Behavior in Older Adults

Heightened reliance on the cerebral cortex for postural stability with aging is well-known, yet the cortical mechanisms for balance control, particularly in relation to balance function, remain unclear. Here we aimed to investigate motor cortical activity in relation to the level of balance challenge presented during reactive balance recovery and identify circuit-specific interactions between motor cortex and prefrontal or somatosensory regions in relation to metrics of balance function that predict fall risk. Using electroencephalography, we assessed motor cortical beta power, and beta coherence during balance reactions to perturbations in older adults. We found that individuals with greater motor cortical beta power evoked following standing balance perturbations demonstrated lower general clinical balance function. Individual older adults demonstrated a wide range of cortical responses during balance reactions at the same perturbation magnitude, showing no group-level change in prefrontal- or somatosensory-motor coherence in response to perturbations. However, older adults with the highest prefrontal-motor coherence during the post-perturbation, but not pre-perturbation, period showed greater cognitive dual-task interference (DTI) and elicited stepping reactions at lower perturbation magnitudes. Our results support motor cortical beta activity as a potential biomarker for individual level of balance challenge and implicate prefrontal-motor cortical networks in distinct aspects of balance control involving response inhibition of reactive stepping in older adults. Cortical network activity during balance may provide a neural target for precision-medicine efforts aimed at fall prevention with aging.

Does increased gait variability improve stability when faced with an expected balance perturbation during treadmill walking?

BACKGROUND

Currently, there is uncertainty as to whether movement variability is errorful or exploratory.

RESEARCH QUESTION

This study aimed to determine if gait variability represents exploration to improve stability. We hypothesized that 1) spatiotemporal gait features will be more variable prior to an expected perturbation than during unperturbed walking, and 2) increased spatiotemporal gait variability pre-perturbation will correlate with improved stability post-perturbation.

METHODS

Sixteen healthy young adults completed 15 treadmill walking trials within a motion simulator under two conditions: unperturbed and expecting a perturbation. Participants were instructed not to expect a perturbation for unperturbed trials, and to expect a single transient medio-lateral balance perturbation for perturbed trials. Kinematic data were collected during the trials. Twenty steps were recorded post-perturbation. Unperturbed and pre-perturbation gait variabilities were defined by the short- and long-term variabilities of step length, width, and time, using 100 steps from pre-perturbation and unperturbed trials. Paired t-tests identified between-condition differences in variabilities. Stability was defined as the number of steps to centre of mass restabilization post-perturbation. Multiple regression analyses determined the effect of pre-perturbation variability on stability.

RESULTS

Long-term step width variability was significantly higher pre-perturbation compared to unperturbed walking (mean difference = 0.28 cm, p = 0.0073), with no significant differences between conditions for step length or time variabilities. There was no significant relationship between pre-perturbation variability and post-perturbation restabilization.

SIGNIFICANCE

Increased pre-perturbation step width variability was neither beneficial nor detrimental to stability. However, the increased variability in medio-lateral foot placement suggests that participants adopted an exploratory strategy in anticipation of a perturbation.

The Effect of Perturbation-Based Balance Training and Conventional Intensive Balance Training on Reactive Stepping Ability in Individuals With Incomplete Spinal Cord Injury or Disease: A Randomized Clinical Trial

Introduction: Impaired balance leads to falls in individuals with motor incomplete spinal cord injury or disease (iSCI/D). Reactive stepping is a strategy used to prevent falls and Perturbation-based Balance Training (PBT) can improve this ability.

Objective: The objective of this study was to determine if PBT results in greater improvements in reactive stepping ability than frequency-matched Conventional Intensive Balance Training (CIBT) in adults with iSCI/D.

Design: Randomized clinical trial.

Setting: Tertiary SCI/D rehabilitation center.

Participants: Twenty-one adults with chronic (>1 year) iSCI/D were randomized. Due to one drop out 20 participants completed the study.

Methods: Participants were randomly allocated to complete either PBT or CIBT three times per week for 8 weeks. Both programs included challenging static and dynamic balance tasks, but the PBT group also experienced manual external balance perturbations.

Main Outcome Measures: Assessments of reactive stepping ability using the Lean-and-Release test were completed at baseline, and after 4 and 8 weeks of training, and 3 and 6 months after training completion. A blinded assessor evaluated secondary outcomes.

Results: Twenty-five participants were screened and 21 consented; one withdrew. Ten PBT and 10 CIBT participants were included in analyses. Across all participants there were improvements in reactive stepping ability (p = 0.049), with retention of improvements at follow up assessments. There were no differences in reactive stepping ability between groups [median (interquartile range): PBT 0.08 (0.68); CIBT 0.00 (0.22)]. One participant in the PBT group experienced a non-injurious fall during training.

Conclusions: Balance training is beneficial for individuals with iSCI/D, but the addition of manual perturbations (i.e., PBT) did not prove advantageous for performance on a measure of reactive stepping ability.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT02960178.

Early Postural Instability in Parkinson's Disease: A Biomechanical Analysis of the Pull Test

Postural instability in Parkinson's disease (PD) is commonly assessed by the pull test. This clinical test may be biased by the variability of the pull force applied. Our objective was to study the postural responses elicited by reproducible pull forces in healthy subjects and PD patients at different stages of the disease. We performed a multimodal approach that included a systematic analysis of the pull force needed to reach the backward limit of stability (FBLoS) assessed by mechanically produced forces, the displacements of the center of pressure (CoP) recorded on a force platform, and the latencies and patterns of activation of the stabilizing muscles. Comparisons between groups were performed by univariate and multivariate statistical analyses. Sixty-four healthy subjects and 32 PD patients, 22 Hoehn-Yahr (H-Y) stages I-II and 10 H-Y stage III, were studied. In healthy subjects, FBLoS decreased with aging and was lower in females. Mean (SD) FBLoS was 98.1 (48.9) Newtons (N) in healthy subjects, 70.5 (39.8) N in PD patients H-Y stages I-II, and 37.7 (18.9) N in PD patients H-Y stage III. Compared to healthy subjects and when adjusted for age and gender, PD patients H-Y stages I-II exhibited the following: (a) a reduced FBLoS; (b) larger CoP displacements and higher velocities for the same applied force; and (c) combined ankle and hip strategies elicited by less intense pull forces. All of these abnormalities were more pronounced in H-Y stage III PD patients compared to H-Y stages I-II PD patients. In conclusion, patients in the early stages of PD already exhibit a degree of postural instability due to inefficient postural adjustments, and they can more easily be destabilized by small perturbations than healthy subjects. This balance impairment becomes more pronounced in more advanced PD. In the pull test, pull force to step back should be a variable to consider when testing balance in clinical practice.

Reactive stepping after a forward fall in people living with incomplete spinal cord injury or disease

STUDY DESIGN

Cross sectional.

OBJECTIVES

To compare the reactive stepping ability of individuals living with incomplete spinal cord injury or disease (SCI/D) to that of sex- and age-matched able-bodied adults.

SETTING

A tertiary SCI/D rehabilitation center in Canada.

METHODS

Thirty-three individuals (20 with incomplete SCI/D) participated. Participants assumed a forward lean position in standing whilst 8-12% of their body weight was supported by a horizontal cable at waist height affixed to a rigid structure. The cable was released unexpectedly, simulating a forward fall and eliciting one or more reactive steps. Behavioral responses (i.e., single step versus non-single step) were compared using a Chi-square test. The following temporal parameters of reactive stepping were compared using t-tests: the onset of muscle activation in 12 lower extremity muscles (six per limb) and step-off, step contact and swing time of the stepping leg.

RESULTS

Behavioral responses were significantly different between groups (χ² = 13.9 and p < 0.01) with participants with incomplete SCI/D showing more non-single step responses (i.e., multi-steps and falls). The onsets of muscle activation were more variable in participants with incomplete SCI/D, but only the stepping tibialis anterior showed a significantly slower onset in this group compared with able-bodied adults (t = -2.11 and p = 0.049). Movement timing of the stepping leg (i.e., step-off, step contact, and swing time) was not significantly different between groups.

CONCLUSIONS

Reactive stepping ability of individuals with incomplete SCI/D is impaired; however, this impairment is not explained by temporal parameters. The findings suggest that reactive stepping should be targeted in the rehabilitation of ambulatory individuals with SCI/D.

Insufficient Balance Recovery Following Unannounced External Perturbations in Persons With Stroke

Background. Persons with stroke (PwS) are at increased risk of falls, especially toward the paretic side, increasing the probability of a hip fracture. The ability to recover from unexpected loss of balance is a critical factor in fall prevention. Objectives. We aimed to compare reactive balance capacity and step kinematics between PwS and healthy controls. Methods. Thirty subacute PwS and 15 healthy controls were exposed to forward, backward, right, and left unannounced surface translations in 6 increasing intensities while standing. Single step threshold, multiple step threshold, and fall threshold (ie, perturbation intensity leading to a fall into harness system) were recorded as well as reactive step initiation time, step length, and step velocity. Results. Twenty-five PwS fell into harness system during the experiment while healthy controls did not fall. Fourteen out of 31 falls occurred in response to surface translations toward the nonparetic side, that is, falling toward the paretic side. Compared with healthy controls, PwS demonstrated significantly lower fall threshold and multiple step threshold in response to forward, backward, and lateral surface translations. Impairments were more pronounced in response to forward surface translation and toward the nonparetic side (ie, loss of balance toward the paretic side). A trend toward significant shorter step length in response to lateral surface translations was found in PwS compared with healthy controls. Conclusions. Findings highlight the importance of assessing reactive balance capacity in response to perturbations in different directions and intensities in addition to the routine assessment in PwS.

The comparison of the effects of physical activity and neurofeedback training on postural stability and risk of fall in elderly women: A single-blind randomized controlled trial

Study Design: This was a single-blind randomized controlled trial. Background: Fall and postural instability are common undesirable consequences of the elderly. Although the benefits of exercise for fall prevention have been demonstrated, the majority of the elderly are physically inactive due to several physical and mental limitations they may face. Another alternative treatment such as neurofeedback with providing additional sensory information may enhance movement performance and so decrease the risk of fall. Objectives: To compare the effects of physical activity and neurofeedback training on postural stability and risk of fall in elderly women. Methods: Forty-five physically independent women who were older than 65 years old, living in the Fereshtegan Elderly Care Center in Shiraz, were recruited and randomly divided into three groups including control, physical activity, and neurofeedback training (15 people in each group). Participants in experimental groups trained for 12 weeks (3 days per week/30 minutes per session). Fall risk and postural stability of participants in all three groups were evaluated before and after intervention using the Biodex Balance System. Results: A mixed model design ANOVA comparing neurofeedback training and physical activity exhibited a significantly greater improvement in both risk of fall and postural stability compared to control (P < .05). Results of post-hoc analysis further indicated that neurofeedback training compared to physical activity can be superior beneficial in reducing risk of fall (P = .005) and improving postural stability (P = .005). There were also significant interactions between group and time of fall risk (P = .0005, ηp² = 0.97) and postural stability (P = .001, ηp² = 0.79). Conclusion: Both neurofeedback and physical activity could be considered as useful alternative for postural stability and balance improvement in elderly women; however, neurofeedback training was more effective than physical activity.

Postural adjustments in anticipation of predictable perturbations allow elderly fallers to achieve a balance recovery performance equivalent to elderly non-fallers

BACKGROUND

In numerous laboratory-based perturbation experiments, differences in the balance recovery performance of elderly fallers and non-fallers are moderate or absent. This performance may be affected by the subjects adjusting their initial posture in anticipation of the perturbation.

RESEARCH QUESTIONS

Do elderly fallers and non-fallers adjust their posture in anticipation of externally-imposed perturbations in a laboratory setting? How does this impact their balance recovery performance?

METHODS

21 elderly non-fallers, 18 age-matched elderly fallers and 11 young adults performed both a forward waist-pull perturbation task and a Choice Stepping Reaction Time (CSRT) task. Whole-body kinematics and ground reaction forces were recorded. For each group, we evaluated the balance recovery performance in the perturbation task, change in initial center of mass (CoM) position between the CSRT and the perturbation task, and the influence of initial CoM position on task performance.

RESULTS

The balance recovery performance of elderly fallers was equivalent to elderly non-fallers (p > 0.5 Kolmogorov-Smirnov test). All subject groups anticipated forward perturbations by shifting their CoM backward compared to the CSRT task (young: 2.1% of lower limb length, elderly non-fallers: 2.7%, elderly fallers: 2.2%, Hodges-Lehmann estimator, p < 0.001 Mann-Whitney U). This backward shift increases the probability of resisting the traction without taking a step.

SIGNIFICANCE

The ability to anticipate perturbations is preserved in elderly fallers and may explain their preserved balance recovery performance in laboratory-based perturbation tasks. Therefore, future fall risk prediction studies should carefully control for this postural strategy, by interleaving perturbations of different directions for example.

The Effect of Active Physical Training Interventions on Reactive Postural Responses in Older Adults: A Systematic Review

BACKGROUND

A variety of physical interventions have been used to improve reactive balance in older adults.

PURPOSE

To summarize the effectiveness of active treatment approaches to improve reactive postural responses in community-dwelling older adults.

DESIGN

Systematic review guided by PRISMA guidelines.

STUDY SELECTION

A literature search included the databases PubMed, OVID, CINAHL, ClinicalTrials.gov, OTseeker, and PEDro up to December 2017. Randomized controlled trials that evaluated quantitative measures of reactive postural responses in healthy adults following participation in an active physical training program were included.

DATA SYNTHESIS

Of 4,481 studies initially identified, 11 randomized controlled trials covering 313 participants were selected for analysis. Study designs were heterogeneous, preventing a quantitative analysis. Nine of the 11 studies reported improvements in reactive postural responses.

CONCLUSIONS

Several clinically feasible training methods have the potential to improve reactive postural responses in older adults; however, conclusions on the efficacy of treatment methods are limited because of numerous methodological issues and heterogeneity in outcomes and intervention procedures.

Intensive Balance Training for Adults With Incomplete Spinal Cord Injuries: Protocol for an Assessor-Blinded Randomized Clinical Trial

BACKGROUND

Impaired reactive balance control can lead to increased falls in people with neurological impairments. Perturbation-based balance training (PBT), which involves repetitive exposure to destabilizing external perturbations, improves the ability to take reactive steps in older adults and individuals who have had a stroke.

OBJECTIVE

The objective is to investigate whether PBT or conventional intensive balance training (CIBT) results in greater improvements in reactive stepping ability in individuals with chronic incomplete spinal cord injury (iSCI).

DESIGN

The design consists of an assessor-blind randomized clinical trial comparing the efficacy of 2 balance training programs (PBT and CIBT) matched for training duration (thrice weekly for 8 weeks).

SETTING

A tertiary spinal cord injury rehabilitation center is used as the setting.

PARTICIPANTS

Participants include 24 adults with iSCI classified as a C or D on the American Spinal Association Impairment Scale, who are able to stand independently and exhibit moderate trunk control.

INTERVENTION

Both PBT and CIBT involve 24 sessions, each 1 hour long, of individualized static and dynamic balance tasks. However, PBT includes external, unexpected balance perturbations provided manually by the trainer at a frequency of roughly 1 per training minute.

MEASUREMENTS

The primary outcome is the ability to recover balance using a single step during the Lean-and-Release test, a novel method of assessing reactive balance. Secondary outcomes include a number of clinical balance and gait assessments, and the number of falls experienced in a 6-month follow-up period. Semi-structured interviews are conducted 3 months after training completion to gain insight into the participants' perceptions of the impact of the interventions.

LIMITATIONS

A control group receiving "standard care" for balance training is not included.

CONCLUSIONS

This trial will provide physical therapists with insight into the efficacy of 2 forms of balance training for individuals with iSCI.

Can Wii Balance? Evaluating a Stepping Game for Older Adults

Decline in balance control is an issue for older adults as it leads to an increased risk of falling which may result in serious injury. Mitigating this risk may be achieved through balance training and exercise, but lack of adherence to an exercise program often occurs. Improvement in balance control may be difficult to quantify in an unbiased manner given the therapist providing the treatment also assesses the patient. We developed a gamified system using an off-the-shelf technology through an iterative feedback with therapists and clients to evaluate a response time during stepping as a measure of balance control. The game was designed using serious game strategies to increase participant engagement. This game included two Nintendo Wii balance boards between which the individual was required to step while the times were recorded. To provide evidence that the system could be used in a clinical environment, we conducted a cross-sectional study collecting data for five minutes at the beginning of a physiotherapy assessment. One hundred and four individuals older than 50 years of age were recruited who were able to step forward with or without an aid. The response time for a step using the system was negatively correlated to the Berg balance score.

Exploring the relationship between stability and variability of the centre of mass and centre of pressure

BACKGROUND

There are competing perspectives in the literature regarding the role of movement variability in quiet standing and balance control. Some view high variability as indicative of poor balance control and a contributor to increased fall risk, whereas others view variability as beneficial in providing sensory information that aids balance control.

RESEARCH QUESTION

This study aimed to help to clarify the role of variability in balance control by testing two competing hypotheses: that increased variability would lead to instability, or that increased variability would improve stability, where stability is defined as the ability to respond to a perturbation.

METHODS

Fourteen healthy young adults (20-35 years old) were recruited. Participants experienced postural perturbations of varying magnitudes, delivered via sudden backward movement of the support surface. Magnitudes of postural perturbation were chosen such that both step and no-step responses could be observed at each magnitude. Variability in the centre of mass and centre of pressure movement was measured for 10 s prior to the postural perturbation. Multiple regression was used to determine if movement variability predicted step responses when controlling for perturbation magnitude, trial order, and margin of stability at perturbation onset.

RESULTS

Lower variability in medio-lateral centre of mass and centre of pressure position, and lower variability in medio-lateral centre of pressure velocity were related to increased odds of stepping in response to the perturbation (p-values ≤0.001).

SIGNIFICANCE

This study provides support for the hypothesis that, at least for relatively low variability values, increased centre of pressure and mass movement variability improves stability. Specifically, increasing movement of the centre of pressure and mass in the medio-lateral direction may help to preserve stability in the antero-posterior direction by providing the central nervous system with information about the antero-posterior centre of mass across a wide range of medio-lateral positions.

Balance Confidence Is Related to Features of Balance and Gait in Individuals with Chronic Stroke

BACKGROUND

Reduced balance confidence is associated with impairments in features of balance and gait in individuals with subacute stroke. However, an understanding of these relationships in individuals at the chronic stage of stroke recovery is lacking. This study aimed to quantify the relationships between balance confidence and specific features of balance and gait in individuals with chronic stroke.

METHODS

Participants completed a balance confidence questionnaire and clinical balance assessment (quiet standing, walking, and reactive stepping) at 6 months postdischarge from inpatient stroke rehabilitation. Regression analyses were performed using balance confidence as a predictor variable, and quiet standing, walking, and reactive stepping outcome measures as the dependent variables.

RESULTS

Walking velocity was positively correlated with balance confidence, whereas mediolateral center of pressure excursion (quiet standing) and double support time, step width variability, and step time variability (walking) were negatively correlated with balance confidence.

CONCLUSIONS

This study provides insight into the relationships between balance confidence and balance and gait measures in individuals with chronic stroke, suggesting that individuals with low balance confidence exhibited impaired control of quiet standing as well as walking characteristics associated with cautious gait strategies. Future work should identify the direction of these relationships to inform community-based stroke rehabilitation programs for individuals with chronic stroke, and determine the potential utility of incorporating interventions to improve balance confidence into these programs.

Elderly Fallers: A Baseline Audit of Admissions to a Day Hospital for Elderly People

Falls in elderly people are a major problem for health and social services because of the incidence of injury and the fear of falling as a disabling consequence (McKee 1998). It seemed that many admissions to a South Buckinghamshire day hospital for elderly people were as a result of falls.

A retrospective and concurrent caseload audit was carried out of medical and occupational therapy notes. The aim of the audit was to establish the incidence of falls among the day hospital population, with a view to improving the quality of the service. The data collected included age, diagnosis, functional ability and consequential actions. These items were included by consensus agreement following a literature review.

Fifty-six of 196 elderly people admitted over the 12-month period had fallen at least once. Of these, 73% had no apparent predisposing factor for their fall and 39% were not carrying out any obvious activity at the time; 59% had an increase in social support due to decreased confidence and mobility after the fall. A multidisciplinary team approach was reinforced and the management of patients' problems on an individual basis was to be continued. The adoption of the audit data collection form as a checklist to facilitate future assessment was recommended.

Preliminary study of measurements of sway in an elderly community population

Postural control seems to deteriorate with advancing age but it is not clear why this happens. As part of a larger epidemiological study of community elderly, a representative sample of 85 people aged 75 and over living at home had assessments of physical and psychological function and measurements of sway and base of support carried out, using a portable force plate. Sway increased with increasing age but there was no difference in sway between men and women. Significant positive associations were found between greater sway and impaired visual acuity, poor nutritional state and reduced mobility. Subjects with various physical impairments tended to have worse balance. Subjects who had had falls did not sway more than non-fallers, but subjects with symptoms of 'dizziness' had a significantly smaller base of support and larger sway than those without, demonstrating an association between objectively impaired balance and subjective symptoms of imbalance.

Relationships between fear of falling, balance confidence, and control of balance, gait, and reactive stepping in individuals with sub-acute stroke

Fear of falling is common in individuals with stroke; however, the associations between fear of falling, balance confidence, and the control of balance and gait are not well understood for this population. This study aimed to determine whether, at the time of admission to in-patient rehabilitation, specific features of balance and gait differed between individuals with stroke who did and did not report fear of falling, and whether these features were related to balance confidence. Individuals with stroke entering in-patient rehabilitation were asked if they were afraid of falling, and completed the Activities-Specific Balance Confidence Scale. Participants performed quiet standing, gait, and reactive stepping tasks, and specific measures were extracted for each (quiet standing: centre of pressure amplitude, between-limb synchronization, and Romberg quotients; gait: walking velocity, double support time, and variability measures; reactive stepping: number of steps, frequency of grasp reactions, and frequency of assists). No significant differences were identified between individuals with and without fear of falling. Balance confidence was negatively related to centre of pressure amplitude, double support time, and step time variability, and positively related to walking velocity. Low balance confidence was related to poor quiet standing balance control and cautious behavior when walking in individuals with sub-acute stroke. While the causal relationship between balance confidence and the control of balance and gait is unclear from the current work, these findings suggest there may be a role for interventions to increase balance confidence among individuals with stroke, in order to improve functional mobility.

Biomechanical Analysis of a Dynamic Stability Test System to Evoke Sway and Step Recovery

This paper reports on the dynamic analysis and experimental validation of a method to perturb the balance of subjects in quiet standing. Electronically released weights pull the subject's waist through a specified displacement sensed by a photoelectric sensor. A dynamic model is derived that computes the force applied to the subject as a function of waist acceleration. This model accurately predicts the acceleration of mock subjects (suspended masses) with high repeatability. The validity and simplicity of this model suggest that this method can provide a standard for provocation testing on stable surfaces. Proof-of-concept trials on human subjects demonstrate that the device can be used with a force platform and motion tracking and that the device can induce both sway and step recoveries in healthy male adults.

Protocol for a randomized controlled clinical trial investigating the effectiveness of Fast muscle Activation and Stepping Training (FAST) for improving balance and mobility in sub-acute stroke

Background

Following stroke, many people have difficulty activating their paretic muscles quickly and with sufficient power to regain their balance by taking quick and effective steps. Reduced dynamic balance and mobility following stroke, or ‘walking balance’, is associated with reduced self-efficacy and restrictions in daily living activities, community integration, and quality of life. Targeted training of movement speeds required to effectively regain balance has been largely overlooked in post-stroke rehabilitation. The Fast muscle Activation and Stepping Training (FAST) program incorporates fast functional movements known to produce bursts of muscle activation essential for stepping and regaining standing balance effectively. The purpose of this study is to: 1) compare the effectiveness of an outpatient FAST program to an active control outpatient physiotherapy intervention in improving walking balance following stroke, and 2) explore potential mechanisms associated with improvements in walking balance.

Methods/Design

This will be an assessor-blinded, parallel group randomized controlled trial design. Sixty participants (30 per group) who have sustained a stroke within the previous six months will be randomly assigned with stratification for lower limb motor recovery to receive twelve 45-minute 1:1 physiotherapy intervention sessions over 6 – 10 weeks in an outpatient setting of either: 1) FAST intervention - systematic and progressive practice of fast squatting and stepping exercises, or 2) active control - conventional physiotherapy directed at improving balance and mobility that includes no targeted fast movement training. The same blinded research physiotherapist will assess outcomes at three time points: 1) baseline (prior to intervention), 2) follow up (within one week post-intervention); and 3) retention (one month post-intervention). The primary outcome is dynamic balance assessed using the Community Balance and Mobility Scale. We will also assess fast and self-selected walking speed, balance self-efficacy, and the ability to respond to internal and external perturbations to balance and associated changes in postural muscle activation.

Discussion

The targeted training of fast functional movements in the FAST program is expected to improve walking balance following stroke compared to the active control intervention. Unique to this study is the investigation of potential mechanisms associated with improvements in walking balance.

Trial registration

NCT01573585

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-014-0187-y) contains supplementary material, which is available to authorized users.

Using the systems framework for postural control to analyze the components of balance evaluated in standardized balance measures: a scoping review

OBJECTIVE

To identify components of postural control included in standardized balance measures for adult populations.

DATA SOURCES

Electronic searches of MEDLINE, EMBASE, and CINAHL databases using keyword combinations of postural balance/equilibrium, psychometrics/reproducibility of results/predictive value of tests/validation studies, instrument construction/instrument validation, geriatric assessment/disability evaluation, gray literature, and hand searches.

STUDY SELECTION

Inclusion criteria were measures with a stated objective to assess balance, adult populations (18y and older), at least 1 psychometric evaluation, 1 standing task, a standardized protocol and evaluation criteria, and published in English. Two reviewers independently identified studies for inclusion. Sixty-six measures were included.

DATA EXTRACTION

A research assistant extracted descriptive characteristics and 2 reviewers independently coded components of balance in each measure using the Systems Framework for Postural Control, a widely recognized model of balance.

DATA SYNTHESIS

Components of balance evaluated in these measures were underlying motor systems (100% of measures), anticipatory postural control (71%), dynamic stability (67%), static stability (64%), sensory integration (48%), functional stability limits (27%), reactive postural control (23%), cognitive influences (17%), and verticality (8%). Thirty-four measures evaluated 3 or fewer components of balance, and 1 measure-the Balance Evaluation Systems Test-evaluated all components of balance.

CONCLUSIONS

Several standardized balance measures provide only partial information on postural control and omit important components of balance related to avoiding falls. As such, the choice of measure(s) may limit the overall interpretation of an individual's balance ability. Continued work is necessary to increase the implementation of comprehensive balance assessment in research and practice.

Balance and muscle power of children with Charcot-Marie-Tooth

BACKGROUND:

In certain diseases, functional constraints establish a greater relationship with muscle power than muscle strength. However, in hereditary peripheral polyneuropathies, no such relationship was found in the literature.

OBJECTIVE:

In children with Charcot-Marie-Tooth (CMT), to identify the impact of muscle strength and range of movement on the static/dynamic balance and standing long jump based on quantitative and functional variables.

METHOD:

The study analyzed 19 participants aged between 6 and 16 years, of both genders and with clinical diagnoses of CMT of different subtypes. Anthropometric data, muscle strength of the lower limbs (hand-held dynamometer), ankle and knee range of movement, balance (Pediatric Balance Scale) and standing long jump distance were obtained by standardized procedures. For the statistical analysis, Pearson and Spearman correlation coefficients were used.

RESULTS:

There was a strong positive correlation between balance and the muscle strength of the right plantar flexors (r=0.61) and dorsiflexors (r=0.59) and a moderate correlation between balance and the muscle strength of inversion (r=0.41) and eversion of the right foot (r=0.44). For the long jump and range of movement, there was a weak positive correlation with right and left plantar flexion (r=0.20 and r=0.12, respectively) and left popliteal angle (r=0.25), and a poor negative correlation with left dorsiflexion (r=-0.15).

CONCLUSIONS:

The data on the patients analyzed suggests that the maintenance of distal muscle strength favors performance during balance tasks, while limitations in the range of movement of the legs seem not to be enough to influence the performance of the horizontal long jump.

Effects of visual biofeedback training for fall prevention in the elderly

[Purpose] The purpose of this study was to investigate the effects of six weeks of visual biofeedback training for prevention of falling in the elderly. The Tetrax system was used for visual biofeedback training. [Subjects and Methods] Thirty elderly persons (experimental group=15, control group=15) who were above 70 and under 80 years of age participated in biofeedback training. They were trained for 15 minutes a day, three times per week. We measured the weight distribution index, stability index, and fall index in the subjects using the Tetrax system, and paired t-tests were used to evaluate the changes before and after intervention. The difference between the groups was compared using an independent t-test. [Results] The experimental group showed significant differences in weight distribution index, stability index, and fall index. The control group showed no significant differences. According to the comparison of training effects between the two groups, the variables of stability index and fall index revealed a statistically significant difference. [Conclusion] The method of visual biofeedback training used in this study should be considered a therapeutic method for the elderly to improve weight distribution, stability, and effectiveness in preventing falls.

Risk factors for falls among older adults: a review of the literature

Falls are one of the major causes of mortality and morbidity in older adults. Every year, an estimated 30-40% of patients over the age of 65 will fall at least once. Falls lead to moderate to severe injuries, fear of falling, loss of independence and death in a third of those patients. The direct costs alone from fall related injuries are a staggering 0.1% of all healthcare expenditures in the United States and up to 1.5% of healthcare costs in European countries. This figure does not include the indirect costs of loss of income both to the patient and caregiver, the intangible losses of mobility, confidence, and functional independence. Numerous studies have attempted to define the risk factors for falls in older adults. The present review provides a brief summary and update of the relevant literature, summarizing demographic and modifiable risk factors. The major risk factors identified are impaired balance and gait, polypharmacy, and history of previous falls. Other risk factors include advancing age, female gender, visual impairments, cognitive decline especially attention and executive dysfunction, and environmental factors. Recommendations for the clinician to manage falls in older patients are also summarized.

Is Impaired Control of Reactive Stepping Related to Falls During Inpatient Stroke Rehabilitation?

Background. Individuals with stroke fall more often than age-matched controls. Although many focus on the multifactorial nature of falls, the fundamental problem is likely the ability for an individual to generate reactions to recover from a loss of balance. Stepping reactions to recover balance are particularly important to balance recovery, and individuals with stroke have difficulty executing these responses to prevent a fall following a loss of balance. Objective. The purpose of this study is to determine if characteristics of balance recovery steps are related to falls during inpatient stroke rehabilitation. Methods. We conducted a retrospective review of individuals with stroke attending inpatient rehabilitation (n = 136). Details of falls experienced during inpatient rehabilitation were obtained from incident reports, nursing notes, and patient interviews. Stepping reactions were evoked using a “release-from-lean” postural perturbation. Poisson regression was used to determine characteristics of stepping reactions that were related to increased fall frequency relative to length of stay. Results. In all, 20 individuals experienced 29 falls during inpatient rehabilitation. The characteristics of stepping reactions significantly related to increased fall rates were increased frequency of external assistance to prevent a fall to the floor, increased frequency of no-step responses, increased frequency of step responses with inadequate foot clearance, and delayed time to initiate stepping responses. Conclusions. Impaired control of balance recovery steps is related to increased fall rates during inpatient stroke rehabilitation. This study informs the specific features of stepping reactions that can be targeted with physiotherapy intervention during inpatient rehabilitation to improve dynamic stability control and potentially prevent falls.

A qualitative review of balance and strength performance in healthy older adults: impact for testing and training

A continuously greying society is confronted with specific age-related health problems (e.g., increased fall incidence/injury rate) that threaten both the quality of life of fall-prone individuals as well as the long-term sustainability of the public health care system due to high treatment costs of fall-related injuries (e.g., femoral neck fracture). Thus, intense research efforts are needed from interdisciplinary fields (e.g., geriatrics, neurology, and exercise science) to (a) elucidate neuromuscular fall-risk factors, (b) develop and apply adequate fall-risk assessment tools that can be administered in clinical practice, and (c) develop and design effective intervention programs that have the potential to counteract a large number of fall-risk factors by ultimately reducing the number of falls in the healthy elderly. This paper makes an effort to present the above-raised research topics in order to provide clinicians, therapists, and practitioners with the current state-of-the-art information.

Reducing fall risk by improving balance control: development, evaluation and knowledge-translation of new approaches

PROBLEM

Falling is a leading cause of serious injury, loss of independence, and nursing-home admission in older adults. Impaired balance control is a major contributing factor.

METHODS

Results from our balance-control studies have been applied in the development of new and improved interventions and assessment tools. Initiatives to facilitate knowledge-translation of this work include setting up a new network of balance clinics, a research-user network and a research-user advisory board.

RESULTS

Our findings support the efficacy of the developed balance-training methods, balance-enhancing footwear, neuro-prosthesis, walker design, handrail-cueing system, and handrail-design recommendations in improving specific aspects of balance control. IMPACT ON KNOWLEDGE USERS: A new balance-assessment tool has been implemented in the first new balance clinic, a new balance-enhancing insole is available through pharmacies and other commercial outlets, and handrail design recommendations have been incorporated into 10 Canadian and American building codes. Work in progress is expected to have further impact.

Percentage height of center of mass is associated with the risk of falls among elderly women: A case-control study

Falls are a serious health problem for aged people, causing social and economic burden. Despite being an important determinant of balance, the positioning of the center of mass (COM) has not been evaluated as a risk factor for falls. This study examined the association between the percentage height of COM (%COM) and the risk of falls in the elderly. Healthy women aged 60 years and older were consecutively selected in a case-control study. Forty-eight individuals classified as "fallers" (having suffered two or more falls in the previous year) were the cases while 48 age and weight-matched women with one fall or no falls in the previous year were the controls ("non-fallers"). Body composition and bone mineral density (BMD) by DXA, 30-second chair stand test, abdominal circumference, Berg's balance scale and %COM using the reaction board method were evaluated in all participants. Body composition parameters were not significantly different between groups. Spine and hip BMD tended to be lower in the fallers, but the difference was significant only at the femoral neck (0.80±0.10g/cm(2) versus 0.87±0.76g/cm(2); p<0.01). Berg's balance scale scores were lower among fallers than non-fallers (p<0.05). Percentage height of COM was significantly higher among fallers (p<0.001) and this was associated with a higher number of fractures (p<0.05). Percentage height of COM is significantly higher in the elderly with frequent falls. Further work is needed in order to determine the value of board reaction measurements in a clinical setting to identify patients at high risk.

Compensatory stepping responses in individuals with stroke: a pilot study

Impaired postural control and a high incidence of falls are commonly observed following stroke. Compensatory stepping responses are critical to reactive balance control. We hypothesize that, following a stroke, individuals with unilateral limb dyscontrol will be faced with the unique challenge of controlling such rapid stepping reactions that may eventually be linked to the high rate of falling. The objectives of this exploratory pilot study were to investigate compensatory stepping in individuals poststroke with regard to: (1) choice of initial stepping limb (paretic or non-paretic); (2) step characteristics; and (3) differences in step characteristics when the initial step is taken with the paretic vs. the non-paretic limb. Four subjects following stroke (38-165 days post) and 11 healthy young adults were recruited. Anterior and posterior perturbations were delivered by using a weight drop system. Force plates recorded centre-of-pressure excursion prior to the onset of stepping and step timing. Of the four subjects, three only attempted to step with their non-paretic limb and one stepped with either limb. Time to foot-off was generally slow, whereas step onset time and swing time were comparable to healthy controls. Two of the four subjects executed multistep responses in every trial, and attempts to force stepping with the paretic limb were unsuccessful in three of the four subjects. Despite high clinical balance scores, these individuals with stroke demonstrated impaired compensatory stepping responses, suggesting that current clinical evaluations might not accurately reflect reactive balance control in this population.

Effect of a perturbation-based balance training program on compensatory stepping and grasping reactions in older adults: a randomized controlled trial

BACKGROUND

Compensatory stepping and grasping reactions are prevalent responses to sudden loss of balance and play a critical role in preventing falls. The ability to execute these reactions effectively is impaired in older adults.

OBJECTIVE

The purpose of this study was to evaluate a perturbation-based balance training program designed to target specific age-related impairments in compensatory stepping and grasping balance recovery reactions.

DESIGN

This was a double-blind randomized controlled trial.

SETTING

The study was conducted at research laboratories in a large urban hospital.

PARTICIPANTS

Thirty community-dwelling older adults (aged 64-80 years) with a recent history of falls or self-reported instability participated in the study.

INTERVENTION

Participants were randomly assigned to receive either a 6-week perturbation-based (motion platform) balance training program or a 6-week control program involving flexibility and relaxation training.

MEASUREMENTS

Features of balance reactions targeted by the perturbation-based program were: (1) multi-step reactions, (2) extra lateral steps following anteroposterior perturbations, (3) foot collisions following lateral perturbations, and (4) time to complete grasping reactions. The reactions were evoked during testing by highly unpredictable surface translation and cable pull perturbations, both of which differed from the perturbations used during training.

RESULTS

/b> Compared with the control program, the perturbation-based training led to greater reductions in frequency of multi-step reactions and foot collisions that were statistically significant for surface translations but not cable pulls. The perturbation group also showed significantly greater reduction in handrail contact time compared with the control group for cable pulls and a possible trend in this direction for surface translations.

LIMITATIONS

Further work is needed to determine whether a maintenance program is needed to retain the training benefits and to assess whether these benefits reduce fall risk in daily life.

CONCLUSION

Perturbation-based training shows promise as an effective intervention to improve the ability of older adults to prevent themselves from falling when they lose their balance.

Role of individual lower limb joints in reactive stability control following a novel slip in gait

Instability after slip onset is a key precursor leading to subsequent falls during gait. The purpose of this study was to determine the impact of reactive muscular response from individual lower limb joints on regaining stability control and impeding a novel and unannounced slip during the ensuing single-stance phase. Ten young adults' resultant moments at three lower limb joints of both limbs, initially derived by an inverse-dynamics approach from empirical data, were optimized to accurately reproduce the original motion before being applied as input to the control variables of their individualized forward-dynamics model. Systematic alteration of the moments of each joint caused corresponding changes in the displacement and velocity of the center of mass (COM) and base of support (BOS) (i.e. their state variables, x(COM), x (COM), x(BOS), x (BOS)), and in the COM stability. The model simulation revealed that these joints had little influence on x (COM) but had substantial impact on x (BOS) reduction, leading to improve the COM stability, mostly from knee flexors, followed by hip extensors, of the slipping limb. Per unit reactive increase in normalized knee flexor or hip extensor moments and per unit reactive reduction in commonly observed plantar-flexor moments could lead to as much as 57.72+/-10.46 or 22.33+/-5.55 and 13.09+/-2.27 units of reduction in normalized x (BOS), respectively. In contrast, such influence was negligible from the swing limb during this period, irrespective of individual variability.

Development of a three-degrees-of-freedom moveable platform for providing postural perturbations

The purpose of this study was to design and develop a three-degrees-of-freedom moveable platform to provide postural perturbations for balance assessment and training. The platform consists of three motion mechanisms, which can provide forward-backward translation, upward-downward tilt, and clockwise-counterclockwise rotation. This platform can move in any of its degrees of freedom separately or simultaneously. The precision and accuracy of the platform movement were examined by calculating the standard deviations in repeated trials and comparing the real amplitude and velocity of the movement with the preset values. All the standard deviations in repeated trials were small in that the variation coefficients were less than 2 per cent, except that in the highest-velocity test, and all the mean differences were less than 1 mm for translational and 1 degree for tilt or rotational perturbations. The results demonstrated that the platform is a reliable and valid instrument for providing postural perturbations. The preliminary investigation of the kinematic postural responses to translational and tilt perturbation showed that this platform is a useful apparatus for balance research. Potential applications of this platform include investigation of the postural responses to yaw rotation or any combination of its degrees of freedom and studying the effects of perturbation-based balance-training programmes provided by this platform.