Investigation of the Effects of Two Types of Locomotion in the Virtual Environment

Virtual Reality (VR) is a technology that enables individuals to engage in a computer-generated, three-dimensional (3D) environment by utilizing specialized electronic equipment. This technology allows users to explore and interact with a wide range of objects and events, enabling them to perform perspective and motor tasks (Frederick P. Brooks, 1999). VR head-mounted displays (HMDs) create full immersion in the virtual environment by projecting images on screens positioned very close to the eyes (Turnbull \& Phillips, 2017).

The quick development of this technology has made it more affordable and available, consequently, its utilization is also increasing. It has applications in various fields, for example, it is widely used as a training platform for astronauts, soldiers, and treatment purposes in rehabilitation (Xie et al., 2021). The reason why many sectors urge to take advantage of VR is because they could promote motor learning by generating an environment, scenario, or activity that allows for the user practice motor skills with simple tools. Simultaneously, VR provides the possibility of repeating the same task at any moment, modifying factors such as level of complexity, time, and intensity of the practice (Lledó et al., 2016).

Despite the great expansion of virtual technology, cybersickness continues to be a problem that prevents it from being used fluently (Tian et al., 2022). Cybersickness is a term established to describe the unpleasant sensation that evokes from the use of virtual reality technology (McCauley \& Sharkey, 1992). Cybersickness appears with symptoms like motion sickness symptoms, the ones we feel while using vehicle such as nausea, dizziness, fatigue, and blurred vision (Laviola, 2000). In various research studies, this phenomenon has been mentioned in different terms, such as simulator sickness or VR sickness. There are several theories trying to explain why individuals develop these symptoms when they are in the car or using HMDs, however, just two theories are considered the most accepted. First theory is the Sensory Conflict Theory that was proposed by Reason \& Brand (1975) while the other one is the Postural Instability Theory, developed by Riccio \& Stoffregen (1991).

There are several factors that affect the severity of cybersickness while using HMDs and some studies have already discussed them (Tian et al., 2022). One of the main factors in Interaction; Navigation method and controllability. Different locomotion styles, such as steering walking, or teleportation, have been investigated to the virtual environment for the purpose of navigating and showed that the choice of the locomotion style would heavily impact the user experience (Al Zayer et al., 2020).

From this point, our study is aiming to compare the difference between the most used locomotion style: controller-based steering, and the Walk in place (WIP), in the context of postural control and cybersickness. We are also planning to investigate other factors affecting the results, such as personal factors; gender, previous experience, and individual's susceptibility to motion sickness.

This study including healthy young volunteers (18-30-year-olds). They started to be collected from November 2023 and will continue until February 2024 in Yeditepe University Physiotherapy and Rehabilitation department laboratory.

Participants will be asked to fill in an online form or conduct a brief interview to collect their demographic information. They will be asked about their age, height (cm), weight (kg), body mass index (BMI), gender (female / male), Medical History, gaming experience, hand and leg preference and Susceptibility to motion sickness. Then, postural stability, motion sickness measurements and heart rate (HR) will be taken before and after each experimental trial.

All Participants will play a game called "Freedom locomotion VR" a 3D virtual environment allowing the player to do several activities in it. All participants will be immerged in this virtual environment twice (two sessions) and have the freedom to do what they like in it. However, In each session, they will use one the two locomotion types that the game provides, the hand controller (HC) based and walking in place (WIP) based locomotion. To compare the effect of each of the two locomotion styles, each participant will play the game two times to be able to try both locomotion types. Postural control, motion sickness symptoms and heart rate will be tested after each session to measure the different in the effect of each type of locomotion.

As this research is including one group who will be measured multiple times in the experiment, repeated measures one-way analysis of variance (ANOVA) would be the best statistical test to use to investigate the difference.


Eligibility Criteria:
Inclusion Criteria:

* Young Adults between 18 and 30 years old.
* Able to understand and follow the researchers' instructions.
* Have no pain or any medical illness.
* Have normal or corrected to normal vision.
* Volunteering to participate in experiments.

Exclusion Criteria:

* Having any medical problem that could affect physical movement or balance (e.g., vestibular, sensory, or musculoskeletal impairments)
* Having any visual problems.
* Having any neurological disorder.
* Using an additional assistive device.
* Have had a middle ear infection in the past month.