**1. Introduction**

Proprioception is the sensation of the position of body parts relative to each other in space, both in statics and during their movement. The formation of proprioceptive sensation occurs due to the activity of various receptor systems located in the tissues of the human body, the largest number of which is in the muscular system. Proprioception belongs to the somatosensory system and is traditionally defined as sensory sensations of position, movement, or balance [1]. From this position, proprioception is the awareness of the position or movement of our body and its parts in space because of processing information from the receptors of muscles, joints, tendons, and skin. This type of sensory sensation includes two

components, the first of which arises in a static position, and the second appears during movement and plays a decisive role in ensuring coordination of movements; both are important in ensuring balance at rest, as well as during movement [2].

The proprioceptive system has a high degree of precision in registering changes recorded by the receptor apparatus, more specifically, a change in the angle in a particular joint or in the mass of a held object. In the process of ontogenesis, the role of proprioception as the dominant receptor system in sensory cognition of the external world goes into second place relative to the visual analyzer, which in humans and mammals acquires a dominant role. However, proprioception continues to be in high demand in building a complete judgment about an external object, providing information about its physical properties necessary to ensure effective interaction with this object, which underlie more complex motor skills that are important for the formation of praxis. Proprioception is actively used as an afferent system for the formation of biofeedback when adjusting the motor system to external conditions in the process of performing a movement and object interaction at the level of the spatial field.

The use of devices for activating proprioceptive sensations as a way to increase sensory immersion in VR or, in another way, to achieve a greater degree of immersion, is one of the unresolved, but actively developing ways to expand the practical application of VR. In VR conditions, sensory perception of reality only through the visual analyzer does not provide the formation of a complete sensory sensation, identical to physical interaction with objects, and cannot be used to implement explicit interaction. It is precisely because of the difficulty of achieving such a quality of proprioceptive sensations, which would be identical to the sensations received in the physical world, that modern VR systems are mostly implicit, and control in them is implemented in surrogate ways that are not identical to the natural richness of object sensations and the complexity of manipulating them.

At the moment, less attention is paid to the study of unimodal proprioceptive information processing in statics or only when performing a movement than the study of multisensory integration processes, with the participation of not only the proprioceptive system, but also other sensory analyzers. Isolated activation of the proprioceptive system is possible only when the visual analyzer is not functioning, which is rarely observed under normal conditions. The close connection between the proprioceptive system and the visual analyzer can be traced through experiments on the formation of proprioceptive sensations, without directly affecting the receptor apparatus. Manipulation of proprioceptive sensations is possible using a visual analyzer, as demonstrated in experiments on the use of mirror therapy in the treatment of phantom pain after limb amputation due to various reasons. In this case, through the information coming through the visual analyzer, it is possible to achieve proprioceptive sensations, sensations of movement, as well as a sense of touch in the complete absence of somatosensory stimuli.

This is evidence that proprioception is a complexly organized bodily sensation, the formation of which can be influenced by the activation of the receptor apparatus of various sensory systems and, of course, primarily the visual analyzer.

### **2. Possibilities of using VR in physical rehabilitation**

One of the main and important applications of VR is its use in the medical field to provide various tasks of physical rehabilitation and habilitation.

The main goal of physical rehabilitation is to help a person return to a natural state when performing daily activities by restoring damaged motor skills, as well as if they cannot be completely restored, acquiring new ones that compensate for those lost due to diseases of the musculoskeletal system (trauma, pathology of

**133**

*Proprioception in Immersive Virtual Reality DOI: http://dx.doi.org/10.5772/intechopen.96316*

motor system in ontogenesis.

problems of motor habilitation.

the mid-1990s.

after stroke [3–6].

the muscular system) or the CNS vascular diseases and injuries. Also, significant prospects for the use of VR are traced in patients with impaired formation of the

Research on the effectiveness of rehabilitation using VR technology appeared in

Currently, there are several systematic reviews evaluating the clinical efficacy of sensorimotor training in VR in restoring the function of the upper limbs and gait

Despite the fact that most often the study of the effectiveness of various methods of motor rehabilitation occurs on the example of such pathologies as acute disorders of cerebral circulation and traumatic brain injury due to their widespread prevalence, the study of the effectiveness of rehabilitation in other pathological conditions using VR technology is also carried out. It should be noted that the nature of movement disorders in various pathologies is accompanied by impairments at various levels of its organization, therefore, modeling various motor tasks under VR conditions allows one to obtain positive results on the restoration of movement in patients with disorders such as infantile cerebral palsy and multiple sclerosis, which are characterized by impaired organization of the motor system at various levels from the cortical to the level of paleokinetic regulation (rubro-spinal) [7]. However, these studies are sporadic and do not allow for a systematic analysis. Thus, VR technology has significant prospects both in the rehabilitation of patients with various dysfunctions of the CNS and musculoskeletal system in the framework of restoration of function within the framework of physical rehabilitation, and in the development of unformed motor skills in the process of solving the

The first reason that makes VR a promising environment for solving a complex of problems of physical habilitation and rehabilitation is that VR can be used to ensure interaction with the outside world by patients with pronounced motor or other limitations [8]. The second important factor is that the VR environment and interaction with its objects can be adapted to the patient's existing physical defect, achieving significant personalization, which, accordingly, will contribute to the

According to the data obtained when assessing the effectiveness of restoration of the motor function of the upper limb in patients after acute cerebrovascular accident in comparison with the group of patients receiving only traditional methods of motor rehabilitation, the use of VR rehabilitation showed great effects both in the short and

A significant advantage of using VR is the ability to automate the rehabilitation process, use the autotune of exercises, obtain objective analytics in the rehabilitation process, and reduce the burden on rehabilitators. If we consider VR from this side, then it can be characterized as a technology that is an interface between the user and various technical devices, which makes it possible to simulate a wide variety of rehabilitation or habilitation environments, which is necessary to solve a whole range of tasks, allowing the rehabilitated to interact with objects of the VR

Thus, the main tasks and prospects of using VR are quite clear, but at the same time they have some limitations in achieving these advantages, relative to tradi-

New approaches to rehabilitation, habilitation or training emerging on the basis of VR are based on the latest technological advances, including the use of robotic devices, tactile interfaces, and brain-computer interfaces. So, the variety of technical devices allows you to more effectively use the capabilities of VR, as an interface between the patient and the outside world, in which you can simulate various

achievement of a more significant effect of rehabilitation or habilitation.

relatively long term (for example, 3 months after the onset of pathology) [9].

environment through a variety of sensory channels.

tional methods of physical rehabilitation or habilitation.

#### *Proprioception in Immersive Virtual Reality DOI: http://dx.doi.org/10.5772/intechopen.96316*

*Proprioception*

components, the first of which arises in a static position, and the second appears during movement and plays a decisive role in ensuring coordination of movements; both are important in ensuring balance at rest, as well as during movement [2]. The proprioceptive system has a high degree of precision in registering changes recorded by the receptor apparatus, more specifically, a change in the angle in a particular joint or in the mass of a held object. In the process of ontogenesis, the role of proprioception as the dominant receptor system in sensory cognition of the external world goes into second place relative to the visual analyzer, which in humans and mammals acquires a dominant role. However, proprioception continues to be in high demand in building a complete judgment about an external object, providing information about its physical properties necessary to ensure effective interaction with this object, which underlie more complex motor skills that are important for the formation of praxis. Proprioception is actively used as an afferent system for the formation of biofeedback when adjusting the motor system to external conditions in the process of performing a movement and object interaction at the level of the spatial field. The use of devices for activating proprioceptive sensations as a way to increase sensory immersion in VR or, in another way, to achieve a greater degree of immersion, is one of the unresolved, but actively developing ways to expand the practical application of VR. In VR conditions, sensory perception of reality only through the visual analyzer does not provide the formation of a complete sensory sensation, identical to physical interaction with objects, and cannot be used to implement explicit interaction. It is precisely because of the difficulty of achieving such a quality of proprioceptive sensations, which would be identical to the sensations received in the physical world, that modern VR systems are mostly implicit, and control in them is implemented in surrogate ways that are not identical to the natural richness

of object sensations and the complexity of manipulating them.

a sense of touch in the complete absence of somatosensory stimuli.

**2. Possibilities of using VR in physical rehabilitation**

to provide various tasks of physical rehabilitation and habilitation.

At the moment, less attention is paid to the study of unimodal proprioceptive information processing in statics or only when performing a movement than the study of multisensory integration processes, with the participation of not only the proprioceptive system, but also other sensory analyzers. Isolated activation of the proprioceptive system is possible only when the visual analyzer is not functioning, which is rarely observed under normal conditions. The close connection between the proprioceptive system and the visual analyzer can be traced through experiments on the formation of proprioceptive sensations, without directly affecting the receptor apparatus. Manipulation of proprioceptive sensations is possible using a visual analyzer, as demonstrated in experiments on the use of mirror therapy in the treatment of phantom pain after limb amputation due to various reasons. In this case, through the information coming through the visual analyzer, it is possible to achieve proprioceptive sensations, sensations of movement, as well as

This is evidence that proprioception is a complexly organized bodily sensation, the formation of which can be influenced by the activation of the receptor apparatus of various sensory systems and, of course, primarily the visual analyzer.

One of the main and important applications of VR is its use in the medical field

The main goal of physical rehabilitation is to help a person return to a natural state when performing daily activities by restoring damaged motor skills, as well as if they cannot be completely restored, acquiring new ones that compensate for those lost due to diseases of the musculoskeletal system (trauma, pathology of

**132**

the muscular system) or the CNS vascular diseases and injuries. Also, significant prospects for the use of VR are traced in patients with impaired formation of the motor system in ontogenesis.

Research on the effectiveness of rehabilitation using VR technology appeared in the mid-1990s.

Currently, there are several systematic reviews evaluating the clinical efficacy of sensorimotor training in VR in restoring the function of the upper limbs and gait after stroke [3–6].

Despite the fact that most often the study of the effectiveness of various methods of motor rehabilitation occurs on the example of such pathologies as acute disorders of cerebral circulation and traumatic brain injury due to their widespread prevalence, the study of the effectiveness of rehabilitation in other pathological conditions using VR technology is also carried out. It should be noted that the nature of movement disorders in various pathologies is accompanied by impairments at various levels of its organization, therefore, modeling various motor tasks under VR conditions allows one to obtain positive results on the restoration of movement in patients with disorders such as infantile cerebral palsy and multiple sclerosis, which are characterized by impaired organization of the motor system at various levels from the cortical to the level of paleokinetic regulation (rubro-spinal) [7]. However, these studies are sporadic and do not allow for a systematic analysis.

Thus, VR technology has significant prospects both in the rehabilitation of patients with various dysfunctions of the CNS and musculoskeletal system in the framework of restoration of function within the framework of physical rehabilitation, and in the development of unformed motor skills in the process of solving the problems of motor habilitation.

The first reason that makes VR a promising environment for solving a complex of problems of physical habilitation and rehabilitation is that VR can be used to ensure interaction with the outside world by patients with pronounced motor or other limitations [8]. The second important factor is that the VR environment and interaction with its objects can be adapted to the patient's existing physical defect, achieving significant personalization, which, accordingly, will contribute to the achievement of a more significant effect of rehabilitation or habilitation.

According to the data obtained when assessing the effectiveness of restoration of the motor function of the upper limb in patients after acute cerebrovascular accident in comparison with the group of patients receiving only traditional methods of motor rehabilitation, the use of VR rehabilitation showed great effects both in the short and relatively long term (for example, 3 months after the onset of pathology) [9].

A significant advantage of using VR is the ability to automate the rehabilitation process, use the autotune of exercises, obtain objective analytics in the rehabilitation process, and reduce the burden on rehabilitators. If we consider VR from this side, then it can be characterized as a technology that is an interface between the user and various technical devices, which makes it possible to simulate a wide variety of rehabilitation or habilitation environments, which is necessary to solve a whole range of tasks, allowing the rehabilitated to interact with objects of the VR environment through a variety of sensory channels.

Thus, the main tasks and prospects of using VR are quite clear, but at the same time they have some limitations in achieving these advantages, relative to traditional methods of physical rehabilitation or habilitation.

New approaches to rehabilitation, habilitation or training emerging on the basis of VR are based on the latest technological advances, including the use of robotic devices, tactile interfaces, and brain-computer interfaces. So, the variety of technical devices allows you to more effectively use the capabilities of VR, as an interface between the patient and the outside world, in which you can simulate various

conditions and tasks, thus achieving a personalized approach to solving rehabilitation problems [10]. In addition to restoring motor skills, VR can be considered as a tool in the treatment of cognitive impairments of various origins, in the treatment of post-traumatic stress disorder, as well as various pain syndromes. One of the promising options for the use of VR is its use in the study of the ontogeny of the nervous system, which will be extremely necessary for understanding the formation of a pathological process, since any pathology in the context of ontogeny can be considered as regressive development, i.e. return to earlier stages of the existence and functioning of the CNS as a whole or its individual components [11]. In this regard, it is extremely important to provide neuro-feedback, preferably multisensory, primarily through the visual and proprioceptive sensory channels, because the formation of motor skills without these sensory systems is not possible. In several studies on the adaptation of the motor system after the demonstrated visual inconsistency of movements in VR to movements in the real physical world, it was found that the activity of the visual-motor connection in children is higher than in adolescents and adults, since such adaptation to motor activity in real in the physical world, after such a demonstration in children, it was much slower [12, 13]. Over time, as they grow older, this connection weakens, but obviously, only because of functional restructuring, and not anatomical, therefore, in a saturated immersive environment, you can get the results of visual-motor interaction, which are not always achievable in the physical world. Thus, a separate study of the motor system, as well as its functioning in health and disease, without connection with sensory systems, is inappropriate and incorrect from a physiological point of view.

VR technology can be used to provide a meaningful and effective impact on various human sensory systems; it also provides significant opportunities for modeling their functioning to compensate for lost sensory and motor functions. Now, the most technically simple VR systems are with implicit interaction with VR objects. These VR environments allow the person to be rehabilitated to act as a passive observer of the displayed content, while interaction occurs through the visual and auditory channel. Some expansion of the application of this technology occurs due to the use of various manipulators or joysticks, while the interaction with VR objects acquires the features of explicit interaction, however, the manipulation of VR objects with the use of these VR devices by objects is surrogate in nature, not giving the fullness of physical sensations.

The main problem in this interaction is the absence of physical sensations provided by the proprioceptive system, namely, the feeling of weight, density of an object, position in space. The importance of these sensations in the process of rehabilitation or habilitation lies in the fact that most of the movements performed by a person are the result of the functioning of the proprioceptive system, which ensures all their diversity and successful performance, regardless of external and internal factors. Thus, locomotor activity, devoid of fine tuning, provided by biofeedback based on the proprioceptive system, becomes less effective, and in some situations it is simply impossible, for example, walking at night or interacting with an object in threedimensional space in the absence of visual control in patients with afferent paresis in the hand. An exception is interaction with objects in three-dimensional space, which is provided by cortical motor centers and the corresponding centers of praxis, in the implementation of which the visual analyzer has an equal or more significant role.
