Elsevier

Gait & Posture

Volume 58, October 2017, Pages 533-538
Gait & Posture

Original article
Virtual obstacle crossing: Reliability and differences in stroke survivors who prospectively experienced falls or no falls

https://doi.org/10.1016/j.gaitpost.2017.09.013Get rights and content

Highlights

  • Stroke survivors often fall during obstacle crossing.

  • Obstacle crossing tasks gained popularity in training and testing in rehabilitation.

  • We assessed reliability of obstacle crossing tasks and their association with prospective falls.

  • Obstacle crossing characteristics became more reliable with increasing obstacle widths.

  • Obstacle crossing characteristics are not associated with prospective falls.

Abstract

Introduction

Stroke survivors often fall during walking. To reduce fall risk, gait testing and training with avoidance of virtual obstacles is gaining popularity. However, it is unknown whether and how virtual obstacle crossing is associated with fall risk.

Aim

The present study assessed whether obstacle crossing characteristics are reliable and assessed differences in stroke survivors who prospectively experienced falls or no falls.

Method

We recruited twenty-nine community dwelling chronic stroke survivors. Participants crossed five virtual obstacles with increasing lengths. After a break, the test was repeated to assess test-retest reliability. For each obstacle length and trial, we determined; success rate, leading limb preference, pre and post obstacle distance, margins of stability, toe clearance, and crossing step length and speed. Subsequently, fall incidence was monitored using a fall calendar and monthly phone calls over a six-month period.

Results

Test-retest reliability was poor, but improved with increasing obstacle-length. Twelve participants reported at least one fall. No association of fall incidence with any of the obstacle crossing characteristics was found.

Discussion

Given the absence of height of the virtual obstacles, obstacle avoidance may have been relatively easy, allowing participants to cross obstacles in multiple ways, increasing variability of crossing characteristics and reducing the association with fall risk.

Conclusion

These finding cast some doubt on current protocols for testing and training of obstacle avoidance in stroke rehabilitation.

Introduction

About 30 to 50% percent of all chronic stroke survivors report at least one fall each year [1] and these falls often result in injuries and medical costs [2]. One of the causes of a fall may be unsuccessful negotiation of an obstacle, resulting in a trip. Indeed, it has been found that obstacle crossing is challenging for elderly and for stroke survivors, as it often results in tripping [3], [4].

Crossing obstacles demands adequate gait adjustments. Several gait adjustments during obstacle crossing in an over ground setting were found to be different in stroke survivors compared to age matched controls [5], [6], [7]. For instance, stroke survivors showed a reduced toe clearance of the affected limb while crossing the obstacle and they also placed their foot at a less favorable position behind the obstacle [6]. Moreover, during over ground obstacle crossing, the peak velocity of the center of mass (CoM) in the medio-lateral (ML) direction was higher in stroke survivors as compared to controls [5], [7]. These gait changes may reduce safety, and it has been shown that the ability to negotiate obstacles successfully is reduced in stroke survivors compared to age matched control groups [5], [8], [9], [10]. Although these differences in over ground obstacle crossing may to some extent explain the higher fall rates in stroke survivors compared to the general older population [5], [7], [9], [11], at present it remains largely unknown whether measures derived from over ground obstacle crossing are associated with falls in stroke survivors. Only one study did find that fall prone stroke survivors were indeed less successful in obstacle crossing as compared to non-fallers [12].

In recent years, obstacle crossing using a virtual environment has gained popularity for testing and training during rehabilitation after a stroke [13], [14]. Training generally aims to enhance the ability to perform stepping adjustments and thereby the ability to walk safely through more complex environments and as such perhaps prevent falls. However, little is known about the reliability and validity of virtual obstacle crossing as a diagnostic tool for fall risk, or as a model for daily life gait. Finally, results found in over ground obstacle crossing may be not transferable to virtual obstacle crossing due to the differences in the experimental set up. For instance, virtual obstacles are two dimensional, and there is no penalty when hitting the obstacle whereas hitting a real obstacle will result in a trip. Therefore, the main aims of the present experiment were to assess test-retest reliability of characteristics of virtual obstacle crossing and assess differences between stroke survivors who experienced falls or no falls. We note here that the data reported were obtained from participants of a previous study that found that steady-state gait characteristics were associated with fall risk [15].

Section snippets

Methods

Participants were community dwelling persons after stroke in the chronic phase, recruited via flyers in hospitals, physical therapy practices, general practitioners and national peer group meetings. Prior to the study, all participants gave written informed consent and the medical ethical committee ‘Noord Brabant’, The Netherlands approved the research protocol (NL49126.028.14).

Participants were excluded if their Functional Ambulation Category (FAC) was lower than three [16], Mini Mental State

Results

A group of twenty-nine stroke survivors derived from a larger cohort [15] participated in the obstacle crossing task. After a six-month follow up, twelve stroke survivors (41%) reported at least one fall, and were classified as fall prone stroke survivors (F). The remaining seventeen stroke survivors (59%) were classified as non-fall prone stroke survivors (NF). None of the reported falls were excluded due to the fall exclusion criteria. The participants in the fall prone group were

Discussion

As virtual obstacle crossing has gained popularity in stroke rehabilitation for training and testing, and since falls occur during obstacle negotiation in daily life [3], [4], we explored whether a virtual obstacle crossing task can function as a diagnostic tool for fall risk. Specifically, the main purpose of the present experiment was to determine test-retest reliability of obstacle crossing characteristics and differences between stroke survivors who prospectively experienced falls or no

Conflict of interest

Michiel Punt was supported by a grant from the Netherlands organization for Scientific Research (NWO #023-003-141). Sjoerd M. Bruijn was supported by a grant from the Netherlands Organization for Scientific Research (NWO #451-12-041).

Acknowledgements

We wish to thank Johannes Gijsbers and Sanne Roeles from Motekforce Link b.v., The Netherlands for his technical support and application development.

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