The retention of fall-resisting behavior derived from treadmill slip-perturbation training in community-dwelling older adults

Strength in arms: empowering older adults against the risk of slipping and falling-a theoretical perspective

Background

Slips and falls are a serious health concern, particularly among older adults. Current physical therapy protocols strengthen the legs to improve balance. However, arm movements help maintain balance during a slip incident. Understanding how arm movements improve balance may help clinicians develop more comprehensive fall-prevention protocols to improve patient outcomes.

Clinical question

What limitations exist in current fall prevention protocols for reducing falls in older adults during slip incidents, and what new strategies can enhance these outcomes?

Key results

Slip incidents often result in a sideways loss of balance, leading to hip fractures in older adults. During a slip, the legs do not produce sideways motion and are less effective in regaining balance in this direction. Contrary, the arms produce 100 + degrees of abduction and this motion reduces falls by 200%+ during a slip incident. Notably, older adults exhibit 35.7% decreased arm abduction acceleration responses compared to younger adults during a slip incident. This delay may be attributed to age-related decreases in type II fibers of the deltoid. High-velocity and ballistic training have been shown to improve the proportion and size of type II fibers as well as improve fall outcomes when focused on the lower extremities.

Clinical application

Therefore, I propose incorporating arm abductor training, alongside leg exercises, as a cost-effective and low-risk intervention to enhance the slip responses in older adults. In light of its minimal risk and considerable potential benefits, starting arm abductor exercises with older adults is a sensible move.

Functional electrical stimulation to enhance reactive balance among people with hemiparetic stroke

BACKGROUND

Individuals with stroke demonstrate a twofold higher fall incidence compared to healthy counterparts, potentially associated with deficits in reactive balance control, which is crucial for regaining balance from unpredictable perturbations to the body. Moreover, people with higher stroke-related motor impairment exhibit greater falls and cannot recover balance during higher perturbation intensities. Thus, they might need supplemental agents for fall prevention or even to be included in a perturbation-based protocol. Functional electrical stimulation is a widely used clinical modality for improving gait performance; however, it remains unknown whether it can enhance or interfere with reactive balance control.

METHODS

We recruited twelve ambulatory participants with hemiparetic stroke (61.48 ± 6.77 years) and moderate-to-high motor impairment (Chedoke-McMaster Stroke Leg Assessment ≤ 4/7). Each participant experienced 4 unpredicted paretic gait-slips, with and without functional electrical stimulation (provided 50-500 ms after perturbation) in random order. The paretic quadriceps muscle group was chosen to receive electrical stimulation, considering the role of support limb knee extensors for preventing limb-collapse. Outcomes including primary (laboratory falls), secondary (reactive stability, vertical limb support) and tertiary (compensatory step length, step initiation, execution time) measures were compared between the two conditions.

RESULTS

Participants demonstrated fewer falls, higher reactive stability, and higher vertical limb support (p < 0.05) following gait-slips with functional electrical stimulation compared to those without. This was accompanied by reduced step initiation time and a longer compensatory step (p < 0.05).

CONCLUSION

The application of functional electrical stimulation to paretic quadriceps following gait-slips reduced laboratory fall incidence with enhanced reactive balance outcomes among people with higher stroke-related motor impairment. Our results lay the preliminary groundwork for understanding the instantaneous neuromodulatory effect of functional electrical stimulation in preventing gait-slip falls, future studies could test its therapeutic effect on reactive balance. Clinical registry number: NCT04957355.

Motor adaptation and immediate retention to overground gait-slip perturbation training in people with chronic stroke: an experimental trial with a comparison group

Background

Perturbation-based training has shown to be effective in reducing fall-risk in people with chronic stroke (PwCS). However, most evidence comes from treadmill-based stance studies, with a lack of research focusing on training overground perturbed walking and exploring the relative contributions of the paretic and non-paretic limbs. This study thus examined whether PwCS could acquire motor adaptation and demonstrate immediate retention of fall-resisting skills following bilateral overground gait-slip perturbation training.

Methods

65 PwCS were randomly assigned to either (i) a training group, that received blocks of eight non-paretic (NP-S1 to NP-S8) and paretic (P-S1 to P-S8) overground slips during walking followed by a mixed block (seven non-paretic and paretic slips each interspersed with unperturbed walking trials) (NP-S9/P-S9 to NP-S15/P-S15) or (ii) a control group, that received a single non-paretic and paretic slip in random order. The assessor and training personnel were not blinded. Immediate retention was tested for the training group after a 30-minute rest break. Primary outcomes included laboratory-induced slip outcomes (falls and balance loss) and center of mass (CoM) state stability. Secondary outcomes to understand kinematic contributors to stability included recovery strategies, limb kinematics, slipping kinematics, and recovery stride length.

Results

PwCS within the training group showed reduced falls (p < 0.01) and improved post-slip stability (p < 0.01) from the first trial to the last trial of both paretic and non-paretic slip blocks (S1 vs. S8). During the mixed block training, there was no further improvement in stability and slipping kinematics (S9 vs. S15) (p > 0.01). On comparing the first and last training trial (S1 vs. S15), post-slip stability improved on both non-paretic and paretic slips, however, pre-slip stability improved only on the non-paretic slip (p < 0.01). On the retention trials, the training group had fewer falls and greater post-slip stability than the control group on both non-paretic and paretic slips (p < 0.01). Post-slip stability on the paretic slip was lower than that on the non-paretic slip for both groups on retention trials (p < 0.01).

Conclusion

PwCS can reduce laboratory-induced slip falls and backward balance loss outcomes by adapting their post-slip CoM state stability after bilateral overground gait-slip perturbation training. Such reactive adaptations were better acquired and retained post-training in PwCS especially on the non-paretic slips than paretic slips, suggesting a need for higher dosage for paretic slips.

Clinical registry number

NCT03205527.

Protective responses of older adults for avoiding injury during falls: evidence from video capture of real-life falls in long-term care

BACKGROUND

falls are common in older adults, and any fall from standing height onto a rigid surface has the potential to cause a serious brain injury or bone fracture. Safe strategies for falling in humans have traditionally been difficult to study.

OBJECTIVE

to determine whether specific 'safe landing' strategies (body rotation during descent, and upper limb bracing) separate injurious and non-injurious falls in seniors.

DESIGN

observational cohort study.

SETTING

two long-term care homes in Vancouver BC.

METHODS

videos of 2,388 falls experienced by 658 participants (mean age 84.0 years; SD 8.1) were analysed with a structured questionnaire. General estimating equations were used to examine how safe landing strategies associated with documented injuries.

RESULTS

injuries occurred in 38% of falls, and 4% of falls caused injuries treated in hospitals. 32% of injuries were to the head. Rotation during descent was common and protective against injury. In 43% of falls initially directed forward, participants rotated to land sideways, which reduced their odds for head injury 2-fold. Upper limb bracing was used in 58% of falls, but rather than protective, bracing was associated with an increased odds for injury, possibly because it occurred more often in the demanding scenario of forward landings.

CONCLUSIONS

the risk for injury during falls in long-term care was reduced by rotation during descent, but not by upper limb bracing. Our results expand our understanding of human postural responses to falls, and point towards novel strategies to prevent fall-related injuries.

Provoking Artificial Slips and Trips towards Perturbation-Based Balance Training: A Narrative Review

Humans' balance recovery responses to gait perturbations are negatively impacted with ageing. Slip and trip events, the main causes preceding falls during walking, are likely to produce severe injuries in older adults. While traditional exercise-based interventions produce inconsistent results in reducing patients' fall rates, perturbation-based balance training (PBT) emerges as a promising task-specific solution towards fall prevention. PBT improves patients' reactive stability and fall-resisting skills through the delivery of unexpected balance perturbations. The adopted perturbation conditions play an important role towards PBT's effectiveness and the acquisition of meaningful sensor data for studying human biomechanical reactions to loss of balance (LOB) events. Hence, this narrative review aims to survey the different methods employed in the scientific literature to provoke artificial slips and trips in healthy adults during treadmill and overground walking. For each type of perturbation, a comprehensive analysis was conducted to identify trends regarding the most adopted perturbation methods, gait phase perturbed, gait speed, perturbed leg, and sensor systems used for data collection. The reliable application of artificial perturbations to mimic real-life LOB events may reduce the gap between laboratory and real-life falls and potentially lead to fall-rate reduction among the elderly community.

Limited transfer and retention of locomotor adaptations from virtual reality obstacle avoidance to the physical world

Locomotor training based in virtual reality (VR) is promising for motor skill learning, with transfer of VR skills in turn required to benefit daily life locomotion. This study aimed to assess whether VR-adapted obstacle avoidance can be transferred to a physical obstacle and whether such transfer is retained after 1 week. Thirty-two young adults were randomly divided between two groups. A control group (CG) merely walked on a treadmill and an intervention group (IG) trained crossing 50 suddenly-appearing virtual obstacles. Both groups crossed three physical obstacles (transfer task) immediately after training (T1) and 1 week later (T2, transfer retention). Repeated practice in VR led to a decrease in toe clearance along with greater ankle plantarflexion and knee extension. IG participants crossed physical obstacles with a lower toe clearance compared to CG but revealed significantly higher values compared to the VR condition. VR adaptation was fully retained over 1 week. For physical obstacle avoidance there were differences between toe clearance of the third obstacle at T1 and the first obstacle at T2, indicating only partial transfer retention. We suggest that perception-action coupling, and thus sensorimotor coordination, may differ between VR and the physical world, potentially limiting retained transfer between conditions.

Perturbation-based balance training: Principles, mechanisms and implementation in clinical practice

Since the mid-2000s, perturbation-based balance training has been gaining interest as an efficient and effective way to prevent falls in older adults. It has been suggested that this task-specific training approach may present a paradigm shift in fall prevention. In this review, we discuss key concepts and common issues and questions regarding perturbation-based balance training. In doing so, we aim to provide a comprehensive synthesis of the current evidence on the mechanisms, feasibility and efficacy of perturbation-based balance training for researchers and practitioners. We address this in two sections: "Principles and Mechanisms" and "Implementation in Practice." In the first section, definitions, task-specificity, adaptation and retention mechanisms and the dose-response relationship are discussed. In the second section, issues related to safety, anxiety, evidence in clinical populations (e.g., Parkinson's disease, stroke), technology and training devices are discussed. Perturbation-based balance training is a promising approach to fall prevention. However, several fundamental and applied aspects of the approach need to be further investigated before it can be widely implemented in clinical practice.

Identification of balance recovery patterns after slips using hierarchical cluster analysis

Accidental falls often result from loss of balance initiated by slips. People may adopt different balance recovery patterns after slips which could affect recovery outcomes. The present study aimed to identify balance recovery patterns after slips and to determine whether these balance recovery patterns could be associated with different levels of slip-induced fall likelihood. Sixty young (age 24.2 ± 2.1 years) participants were involved in an experimental study. They were instructed to walk on a linear walkway, where unexpected slips were induced when stepping onto a removable vinyl tile sheet covered with water-detergent mixture. One hundred and fifty slip trials were obtained, including 85 successful balance recovery trials and 65 failed balance recovery trials (i.e., fall trials). Hierarchical cluster analysis was used to classify balance recovery patterns based on the kinematic measures of both feet over the period from 100 to 300 ms after heel contact of the slipping foot. Three balance recovery patterns were identified, and these balance recovery patterns were found to be associated with different levels of slip-induced fall likelihood. Findings from the present study can contribute to better understanding of balance recovery mechanisms associated with slips, and guide developing and evaluating fall prevention interventions.

Can a single session of treadmill-based slip training reduce daily life falls in community-dwelling older adults? A randomized controlled trial

BACKGROUND

Task-specific training with single-session overground slip simulation has shown to reduce real-life falls in older adults.

AIMS

The purpose of this study was to determine if fall-resisting behavior acquired from a single-session treadmill-based gait slip training could be retained to reduce older adults' falls in everyday living over a 6-month follow-up period.

METHODS

143 community-dwelling older adults (≥ 65 years old) were randomly assigned to either the treadmill-based gait slip training group (N = 73), in which participants were exposed to 40 unpredictable treadmill slips, or the control group (N = 70), in which participants walked on a treadmill at their comfortable speed. Participants reported their falls from the preceding year (through self-report history) and over the following 6 months (through fall diaries and monitored with phone calls).

RESULTS

There was no main effect of time (retrospective vs. prospective fall) and training (treadmill training vs. control) on fall reduction (p > 0.05 for both). The survival distributions of event of all-cause falls or slip falls were comparable between groups (p > 0.05 for both).

DISCUSSION

Unlike overground slip training where a single training session could significantly reduce everyday falls in a 6-month follow-up period, the results indicated that one treadmill-based gait slip training session by itself was unable to produce similar effects.

CONCLUSION

Further modification of the training protocol by increasing training dosage (e.g., number of sessions or perturbation intensity) may be necessary to enhance transfer to daily living. This study (NCT02126488) was registered on April 30, 2014.

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.

Biomechanical Mechanisms of Improved Balance Recovery to Repeated Backward Slips Simulated by Treadmill Belt Accelerations in Young and Older Adults

Aim: Exposure to repeated gait perturbations improves the balance of older adults (OAs) and decreases their risks of falling, but little is known about the underpinning mechanical adjustments. We aimed to quantify the changing temporo-spatial and kinetic characteristics of balance recovery following repeated backward slips to better understand the mechanical adjustments responsible for improved balance.

Methods: We exposed 17 young adults (YAs) (25.2 ± 3.7 years) and 17 OAs (62.4 ± 6.6 years) to 10 backward slips simulated on an instrumented treadmill by unilateral backward belt accelerations. We measured the balance of the participants (margin of stability: MoS), balance recovery (n_steps: number of steps necessary to return to a steady gait for at least three consecutive steps), temporo-spatial (step length), and kinetics [ground reaction force (GRF) angle, lower limb joint moments] for 15 steps following each slip. The results were compared with baseline.

Results: Participants in both groups improved their MoS and n_steps with repeated exposure to the slips, but no significant effect of age was detected. During the perturbed step, the GRF vector was directed more posteriorly during mid-stance and more anteriorly during push-off than baseline, which resulted in a longer step. These adjustments were maintained from the first (Slip01) to the last (Slip10) slip, and by Slip10 were correlated with better balance (MoS) on the second recovery step. During the first recovery step following Slip01, participants developed lower plantarflexor and larger knee extensor moments whilst taking a shorter step, these adjustments were correlated with poorer balance and were not maintained with repeated slips. Joint moments and step length of the first recovery step returned to normal levels by Slip10.

Conclusion: Young adults and OAs improved their balance with repeated slips. The adjustments that were positively correlated with balance (changes in step length, GRF angle) were maintained whilst those that were not (changes in joint moments) were discarded. All the responses observed in Slip10 were observed in Slip01. The observed balance improvements were achieved by refining the initial strategy rather than by developing a new one. The underlying mechanics were correlated with step length of the first recovery steps, which was associated with balance and should be monitored in fall prevention interventions.