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