Virtual reality for gait rehabilitation: Effect and effectiveness of virtual reality and optic flow in a neurological population

Being able to walk independently is considered to be one of the key goals of neurorehabilitation. Gait rehabilitation programs need to be task-specific, repetitive, and intensive in order to enhance neuroplasticity, which is vital to induce locomotor changes. Conventional rehabilitation techniques such as overground walking training or treadmill training have limits that can undermine their efficacy and usability. Maintaining a high level of participation and motivation during these conventional rehabilitation programs can become difficult for patients due to the repetitive movements and monotonous practice environments. Research on innovative ways to enhance conventional gait training programs is therefore imperative.
Virtual reality-enhanced gait training is one of these research domains where a lot has happened in recent years. Virtual reality has the potential to increase relevant concepts of neuroplasticity by providing gait training in more interactive, enriched, and motivating environments. However, research on this topic has primarily assessed the deployment effect (i.e. the effect that using or not using virtual reality has), leaving much unclear about the effect of the used virtual reality device and the design and characteristics of a virtual training environment to optimally enhance gait rehabilitation programs. Thus, an important next step in this research domain is to understand how implementing and manipulating valuable principles in the virtual environment influences patients’ locomotion and can be used during virtual reality-enhanced training programs, using cross-sectional studies.
First, this thesis synthesizes the published evidence on the effectiveness of virtual reality for the rehabilitation of the gait function in neurological patients (Chapter One). In a next step, this thesis reports the findings of two cross-sectional studies focusing on the effect of adding virtual reality and manipulating the speed of optic flow while walking (Chapters Two, Three, and Four). More precisely, chapter two examined the effect of adding fully immersive virtual reality and manipulating the speed of optic flow during robot-assisted treadmill walking in a healthy population; chapter three examined the effect of adding semi-immersive virtual reality and manipulating the speed of optic flow during self-paced treadmill walking both in stroke survivors and healthy people; and chapter four examined the effect of adding fully immersive virtual reality, manipulating the speed of optic flow during self-paced treadmill walking both in stroke survivors and healthy people, and the effect of the level of immersion.
Summarized, the results of this thesis suggest that there is growing evidence supporting the use of virtual reality for the rehabilitation of the gait function in people with neurological disorders. To date, most evidence can be found for the rehabilitation of chronic, ambulatory stroke survivors. In this subgroup, the addition of virtual reality during treadmill walking seems to be effective to improve gait-related outcome measures. Moreover, virtual reality-enhanced treadmill walking is safe and enjoyable, with minor or no adverse events being reported. Concerning the use of optic flow speed manipulations to enhance gait training, only small effects on the stroke survivors’ locomotion were reported. Though, it is suggested that fully immersive virtual reality devices could elicit a greater effect compared to less immersive virtual reality devices. Before optic flow speed manipulations can be implemented in therapy, additional work is needed to further optimize the type of optic flow speed manipulation and to elicit a greater effect on gait outcomes.
To conclude, although this thesis offers interesting insights on the effectiveness and usability of virtual reality as a rehabilitation tool for patients with neurological disorders, it also raises some questions and opportunities for further research. There are still numerous aspects of virtual reality interventions to enhance gait training that remain to be unravelled in the years to come.