High contextual interference in perturbation-based balance training leads to persistent and generalizable stability gains of compensatory limb movements

Judokas Show Increased Resilience to Unpredictable Stance Perturbations

Combat sports are characterized by frequent large-scale stance perturbations that may lead to falls. In the present investigation, we compared compensatory arm and leg movements in response to unpredictable stance perturbations between judokas and other athletes whose sports present reduced balance demand, relative to combat sports. Specifically, we tested judokas (n = 9), and a group of swimmers and runners (n = 11, controls) in sudden support base displacements in the mediolateral direction, generated by a movable electronic platform, in the following modes: (a) rotation, (b) translation, and (c) combined rotation-translation. The platform was displaced to either side, in three peak velocities (cm/second or ^o/second) of 20 (low), 30 (moderate), or 40 (high), resulting in 18 distinct perturbations. We evaluated postural responses with a scale for analyzing the stability of compensatory arm and leg movements (CALM). Results showed that, in the most challenging perturbations, judokas had higher stability scores (arm, leg, and global) than did the comparison group. Higher scores for judokas reflected their increased rate of motionless arm and leg responses and absence of near-falls, compared to 30% falls in the most challenging perturbations for the swimmers and runners. As a practical application, judo training may help achieve stable compensatory limb movements in a way that parallels the benefits obtained from perturbation-based balance training in laboratory settings.

Effects of treadmill slip and trip perturbation-based balance training on falls in community-dwelling older adults (STABILITY): study protocol for a randomised controlled trial

INTRODUCTION

Falls among older adults are most frequently caused by slips and trips and can have devastating consequences. Perturbation-based balance training (PBT) have recently shown promising fall preventive effects after even small training dosages. However, the fall preventive effects of PBT delivered on a treadmill are still unknown. Therefore, this parallel-group randomised controlled trial aims to quantify the effects of a four-session treadmill-PBT training intervention on falls compared with treadmill walking among community-dwelling older adults aged 65 years or more.

METHODS AND ANALYSIS

140 community-dwelling older adults will be recruited and randomised into either the treadmill-PBT or the treadmill walking group. Each group will undergo three initial training sessions within a week and an additional 'booster' session after 26 weeks. Participants in the treadmill-PBT group will receive 40 slip and/or trip perturbations induced by accurately timed treadmill belt accelerations at each training session. The primary outcome of interest is daily life fall rates collected using fall calendars for a follow-up period of 52 weeks. Secondary outcomes include physical, cognitive and social-psychological fall-related risk factors and will be collected at the pre-training and post-training test and the 26-week and 52-week follow-up tests. All outcomes will be analysed using the intention-to-treat approach by an external statistician. A Poisson's regressions with bootstrapping, to account for overdispersion, will be used to compare group differences in fall rates.

ETHICS AND DISSEMINATION

The study protocol has been approved by the North Denmark Region Committee on Health Research Ethics (N-20200089). The results will be disseminated in peer-reviewed journals and at international conferences.

TRIAL REGISTRATION NUMBER

NCT04733222.

The Effectiveness of Perturbation-Based Training in the Treatment of Patients With Stroke: A Systematic Review and Meta-Analysis

Purpose:

To investigate the effectiveness of perturbation-based training (PBT) on balance and balance confidence in patients with stroke.

Methods:

Systematic searching was performed from inception to November 2021. The inclusion criteria were RCTs assessed the effectiveness of PBT in patients with stroke. Data regarding participants, intervention parameters, outcome measures, follow-up, and main results were extracted. The outcomes were balance and balance confidence. Methodological quality and quality of evidence were assessed using the Physiotherapy Evidence Database (PEDro) scale and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system; respectively.

Data analysis:

A total of 7 articles )271 patients) were included. A meta-analysis using a random-effect model was performed on 6 studies. Standardized mean difference (SMD) with a 95% confidence interval was calculated for balance and balance confidence.

Results:

PEDro scale revealed 5 good-quality and 2 fair-quality studies. The currently available evidence showed significant effect of PBT in improving balance (SMD 0.60 [95% CI 0.15-1.06]; P = .01; very low-quality evidence) and non-significant in improving balance confidence (SMD 0.11 [95% CI −0.24 to 0.45]; P = .55; low-quality evidence).

Conclusion:

PBT may improve balance in patients with stroke, however its effect on balance confidence was limited. The quality of the evidence was low or very low with little confidence in the effect estimate, which suggests further high-quality trials are required.

Registration:

PROSPERO registration number (CRD42021291474).

Vigor of reactive postural responses is set from feedback and feedforward processes

I explore a distinct perspective from that brought in the book by arguing that in postural control our organism selects the vigor of reactive responses guided by an optimization rule considering first the required postural response for balance recovery as indicated by afferent information from a myriad of sensory receptors, and second the history of previous responses to similar perturbations.

Unconstrained slip mechanics and stepping reactions depend on slip onset timing

Slips can occur at any time during stance. Accordingly, time-dependent tangential ground reaction forces likely produce a diverse range of slipping foot mechanics when traction is lost, thus requiring flexible recovery strategies to prevent falls. However, previous research has focused on slip onset in early stance, often with experimental anteroposterior constraints on the slipping foot, despite the diversity of environmental slips and falls. This study aimed to determine the effects of slip onset time on slip direction, severity (distance and velocity), and compensatory stepping responses. Ten young adults received slipping perturbations at different times during the stance phase of walking via a wearable device that reduces available friction while allowing the slipping foot to slide freely within the horizontal plane. Slip direction, distance, and peak velocity, compensatory step direction and distance, and upper body angular momentum magnitude and plane of rotation were derived from kinematic data. All outcome measurements significantly correlated with the time of slip onset. Slip direction and the plane of rotation of angular momentum deviated widely from the sagittal plane, exhibiting laterally-directed components exceeding those in the anteroposterior direction. As slip onset occurred later in stance, slip severity decreased while compensatory steps became longer and progressed from a posterior to anterior placement. These results provide insight into critical times within stance when slips are most severe, and into the diversity of slipping mechanics caused by changes in slip onset time.

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.

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).

Development and piloting of a perturbation stationary bicycle robotic system that provides unexpected lateral perturbations during bicycling (the PerStBiRo system)

Background

Balance control, and specifically balance reactive responses that contribute to maintaining balance when balance is lost unexpectedly, is impaired in older people. This leads to an increased fall risk and injurious falls. Improving balance reactive responses is one of the goals in fall-prevention training programs. Perturbation training during standing or treadmill walking that specifically challenges the balance reactive responses has shown very promising results; however, only older people who are able to perform treadmill walking can participate in these training regimes. Thus, we aimed to develop, build, and pilot a mechatronic Perturbation Stationary Bicycle Robotic system (i.e., PerStBiRo) that can challenge balance while sitting on a stationary bicycle, with the aim of improving balance proactive and reactive control.

Methods

This paper describes the development, and building of the PerStBiRo using stationary bicycles. In addition, we conducted a pilot randomized control trial (RCT) with 13 older people who were allocated to PerStBiRo training (N = 7) versus a control group, riding stationary bicycles (N = 6). The Postural Sway Test, Berg Balance Test (BBS), and 6-min Walk Test were measured before and after 3 months i.e., 20 training sessions.

Results

The PerStBiRo System provides programmed controlled unannounced lateral balance perturbations during stationary bicycling. Its software is able to identify a trainee’s proactive and reactive balance responses using the Microsoft Kinect™ system. After a perturbation, when identifying a trainee’s trunk and arm reactive balance response, the software controls the motor of the PerStBiRo system to stop the perturbation. The pilot RCT shows that, older people who participated in the PerStBiRo training significantly improved the BBS (54 to 56, p = 0.026) and Postural Sway velocity (20.3 m/s to 18.3 m/s, p = 0.018), while control group subject did not (51.0 vs. 50.5, p = 0.581 and 15 m/s vs. 13.8 m/s, p = 0.893, respectively), 6MWT tended to improve in both groups.

Conclusions

Our participants were able to perform correct balance proactive and reactive responses, indicating that older people are able to learn balance trunk and arm reactive responses during stationary bicycling. The pilot study shows that these improvements in balance proactive and reactive responses are generalized to performance-based measures of balance (BBS and Postural Sway measures).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-021-02015-1.

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.

Asymmetric interlateral transfer of motor learning in unipedal dynamic balance

Interlateral transfer of learning between the legs in body balance training is a topic of theoretical and practical interest, but it has been left untouched in previous research. In this investigation, we aimed to evaluate the magnitude and asymmetry of interlateral transfer of balance stability following the practice of a challenging task of unipedal support on an unstable base. Thirty participants (18-30 years old) were assigned to two groups practicing either with the right or the left leg. Training consisted of a single practice session of unipedal balance on a platform free to sway in the anteroposterior direction. Balance time (off ground) of either leg in 10-s trials was compared across pre-test, post-test, and 7-day retention. Post-test indicated that both groups had similar performance gains with the trained leg, and equivalent transfer to the transfer leg. Analysis of retention indicated further balance improvement with both transfer legs, while practice with the right leg led to the superior transfer to the untrained leg as compared to the opposite transfer direction. These results suggest that persistent transfer of learning effects for unipedal dynamic balance is bilateral but more prominent in the right-to-left direction.