Elsevier

Clinical Biomechanics

Volume 67, July 2019, Pages 171-179
Clinical Biomechanics

A pilot study of reactive balance training using trips and slips with increasing unpredictability in young and older adults: Biomechanical mechanisms, falls and clinical feasibility

https://doi.org/10.1016/j.clinbiomech.2019.05.016Get rights and content

Highlights

  • Exposure to unpredictable slips and trips can improve balance recovery in young and older adults.

  • Increased anxiety and a high dropout rate were observed in older adults.

  • Training of balance recovery may require more individualised training over multiple days.

Abstract

Background

Exposure to unpredictable trips and slips can improve balance recovery responses but it was not known if older adults can tolerate such high intensity training. The study aim was to determine if reactive balance in both young and older adults could be trained in a single day through exposure to slip and trip hazards hidden in unpredictable walkway locations.

Methods

Ten young (20-40 yr) and ten older adults (65 + yr) completed 32 trials on a 10-meter trip and slip walkway; 14 slip trials, 14 trip trials and 4 no-perturbation trials presented in a pseudo-random order. Participant usual gait speed was regulated using a metronome and stepping tiles at fixed distances. Gait kinematics (Vicon motion capture), falls (> 30% body weight into the harness), anxiety and confidence to avoid falling were assessed.

Findings

Margin of stability for balance recovery after slips substantially improved at training completion for older adults (effect size = 1.13, P = 0.019). Falls from slips also decreased: 44.4% to 0% in the young adults; and 28.6% to 14.3% in the older adults. Although confidence to avoid falling did not change, anxiety increased during training with one young and three older participants withdrawing during training.

Interpretations

The findings indicate exposure to unpredictable perturbations improves reactive balance in young and older adults. However, improvements of balance recovery from trips were not significant. Elevated anxiety levels and a high dropout rate suggest the need for more individualised training over multiple days.

Introduction

Falls in older age can result in fractures and fear and can trigger a decline in physical function and loss of independence (Centers for Disease Control and Prevention, 2006). Falls in the community setting are often caused by trips and slips during walking (Berg et al., 1997) and impaired reactive balance against trip and slip hazards have been identified as key risk factors for falls (Maki et al., 2003; Rogers et al., 1996; Woollacott and Tang, 1997; Young et al., 2013).

Earlier studies have shown that reactive balance can be modulated and improved by exposure to repeated perturbations (Nashner, 1980; Pavol et al., 2002; Pavol et al., 2004; Quintern et al., 1985). Thus, the use of mechanical postural perturbations in a safe environment has been proposed as a training method to prevent falls (Pai and Bhatt, 2007; Shimada et al., 2004). Preliminary systematic review evidence suggests that reactive balance training (also called “perturbation-based balance training”) can prevent falls by approximately 50% in older populations (Mansfield et al., 2015; Okubo et al., 2017). Previous studies have used a variety of methods to present postural perturbations and different methods are likely to yield different training effects, with most effective and feasible methodology yet to be determined (Gerards et al., 2017; McCrum et al., 2017).

Treadmills with abrupt belt accelerations (Shimada et al., 2004), ankle pulls (Karamanidis et al., 2011) or obstacles (Schillings et al., 1996) have been used to produce slip-like and trip-like simulations of balance loss. Over-ground walkways concealing hazards have higher ecological validity, but previous studies have often used a single hazard type (e.g. a sliding plate) in a detectable or known fixed location. Such prior knowledge of the hazard location and type can be used to make predictive (i.e. feedforward or proactive) changes in the approach (e.g. shorter step lengths) and anticipatory postural adjustments (e.g. anterior centre of mass [CoM] shift) prior to an expected slip or trip (Bhatt et al., 2006; Liu et al., 2017; Wang et al., 2011; Yang and Pai, 2013). These predictive changes to the approach may cause significant bias in the assessment of balance recovery reactions (i.e. feedback control of balance and stepping after hazard initiation) (Bohm et al., 2015). Changes in the approach may also reduce the need for a rapid response and therefore the efficacy of reactive balance training.

To address the issue of hazard predictability, we designed a perturbation system that can expose participants to unexpected slips and trips in various concealed locations while controlling for gait speed, step length and cadence (Brodie et al., 2018; Okubo et al., 2018). Since this perturbation system can generate repeated slips and trips while maintaining high unpredictability, it should enable specific training of rapid balance recovery reactions (Bierbaum et al., 2011; Bohm et al., 2015); however, it is not known if young and older adults can tolerate this high level of unpredictability. The purpose of this study was to examine and compare the effects of reactive balance training for young and older adults on: (i) the biomechanical parameters of a step immediately before and after a perturbation; (ii) falls; and (iii) clinical feasibility. We hypothesized that the reactive balance training protocol would be feasible and result in improved balance recovery responses and fewer falls with minimum predictive gait alterations.

Section snippets

Participants

A convenience sample was used for this pilot study. Ten young adults aged 20 to 40 years and ten older adults aged 65 to 90 years were recruited from the NeuRA Research Volunteer Registry (HC14320) and institute staff. Inclusion criteria were independent living community or retirement village residents, no osteoporosis or neurological impairment restricting activities of daily living, no history of fractures in the past 3 years, and able to stand or walk for 20 min without support. The above

Baseline characteristics

The demographic and usual gait characteristics of the young (4 females/6 males) and older (9 females/1 male) participants (mean [standard deviation]) are presented in Table 2. Compared to the young counterparts, older participants were significantly shorter in height and step length. No other characteristics showed a significant between-group difference (P > 0.05).

Normal walk trials

During the normal walks (unperturbed trials) the older participants walked significantly slower (1.13 [0.3] ms−1 vs 1.35 [0.08] ms−1

Biomechanical mechanisms

In the older participants, repeated exposure to unpredictable perturbations successfully induced large improvements in stability (MoS) during the first recovery step after slips. The participants managed to reduce the slip speed to the extent that it may be no longer hazardous (< 1.0 m/s) (Moyer et al., 2006) and was likely the major contributor to the smaller backward XCoM displacement and improved MoS during recovery. We assumed this increased stability was primarily related to improved

Conclusions

Reactive balance training using unexpected trip and slip hazards may provide an ecologically valid simulation of real life balance recovery biomechanics. The improved margin of stability and the non-significant reduction in fall rates (in absence of changes to approach kinematics) suggests that older adults can improve their balance recovery reactions in a single day. However, the high dropout rate and elevated anxiety during training suggests this protocol may not be suitable for all older

Contributions

YO, SRL, MAB and DLS contributed to the conception and design of the study. YO and CH recruited participants, conducted the experiments and collected data. YO and MAB processed and analysed the data. YO drafted the article. SRL, MAB, DLS and CH revised the article for important intellectual content. All authors approved the final version.

Declaration of Competing Interest

We declare we have no conflicting interest related to this manuscript.

Acknowledgements

We express our thanks to all the participants of this study. We especially thank Hilary Carter for developing and maintaining the slip and trip walkway. YO was supported by a Japan Society for the Promotion of Science fellowship. YO and MAB currently receive support from a National Health and Medical Research Council (NHMRC) Program Grant (#1055084). SRL holds an NHMRC research fellowship.

Funding

This work was supported by the National Health and Medical Research Council (Program Grant #1055084, 2014-2018). The funding source was not involved in the conduct of the research or preparation of the manuscript.

References (56)

  • M. Pijnappels et al.

    Tripping without falling; lower limb strength, a limitation for balance recovery and a target for training in the elderly

    J. Electromyogr. Kinesiol.

    (2008)
  • M.W. Rogers et al.

    Stimulus parameters and inertial load: effects on the incidence of protective stepping responses in healthy human subjects

    Arch. Phys. Med. Rehabil.

    (1996)
  • A.M. Schillings et al.

    Mechanically induced stumbling during human treadmill walking

    J. Neurosci. Methods

    (1996)
  • R. Senden et al.

    The influence of age, muscle strength and speed of information processing on recovery responses to external perturbations in gait

    Gait Posture

    (2014)
  • F. Suptitz et al.

    Dynamic stability control during perturbed walking can be assessed by a reduced kinematic model across the adult female lifespan

    Hum. Mov. Sci.

    (2013)
  • J.H. Van Dieen et al.

    Age-related intrinsic limitations in preventing a trip and regaining balance after a trip

    Saf. Sci.

    (2005)
  • T.Y. Wang et al.

    Generalization of motor adaptation to repeated-slip perturbation across tasks

    Neuroscience

    (2011)
  • T.Y. Wang et al.

    Adaptive control reduces trip-induced forward gait instability among young adults

    J. Biomech.

    (2012)
  • F. Yang et al.

    Alteration in community-dwelling older adults' level walking following perturbation training

    J. Biomech.

    (2013)
  • F. Yang et al.

    Automatic recognition of falls in gait-slip training: harness load cell based criteria

    J. Biomech.

    (2011)
  • P.M. Young et al.

    Leg preference associated with protective stepping responses in older adults

    Clin. Biomech.

    (2013)
  • W.P. Berg et al.

    Circumstances and consequences of falls in independent community-dwelling older adults

    Age Ageing

    (1997)
  • T. Bhatt et al.

    Immediate and latent interlimb transfer of gait stability adaptation following repeated exposure to slips

    J. Mot. Behav.

    (2008)
  • T. Bhatt et al.

    Adaptive control of gait stability in reducing slip-related backward loss of balance

    Exp. Brain Res.

    (2006)
  • S. Bohm et al.

    Predictive and reactive locomotor adaptability in healthy elderly: a systematic review and meta-analysis

    Sports Med.

    (2015)
  • M. Brodie et al.

    Optimizing successful balance recovery from unexpected trips and slips

    J. Biomed. Sci. Eng.

    (2018)
  • Centers for Disease Control and Prevention

    Fatalities and injuries from falls among older adults — United States, 1993–2003 and 2001–2005

    MMWR Morb. Mortal. Wkly Rep.

    (2006)
  • J. Cohen

    A power primer

    Psychol. Bull.

    (1992)
  • Cited by (19)

    • Reactive balance responses to a trip and slip during gait in people with multiple sclerosis

      2021, Clinical Biomechanics
      Citation Excerpt :

      Initially, participant's usual gait speed, step length and cadence were assessed three times on a 5 m electronic mat (GAITRite mat, v4.0, 2010 CIR Systems). To assess reactive balance against a trip and a slip during gait, the Trip and Slip Walkway, an experimental setup detailed in previous studies (Okubo et al., 2018; Okubo et al., 2019a; Okubo et al., 2019b) was used. In short, the walkway is 10 m long consisting of 40 wooden tiles (50 × 50 cm) that disguise a trip tile and a slip tile.

    View all citing articles on Scopus
    View full text