VR legs is a term used in the field of virtual reality (VR) to characterize the user habituation to the virtual environment. The Urban Dictionary describes it as “the metaphorical representation of being accustomed to immersion in a virtual reality environment, particularly in regards to virtual locomotion.” VR legs are therefore related to simulator sickness, and since the release to the general public of new VR devices, users and developers have been dealing with this problem, and trying to find ways to overcome it   (1; 2).
VR Legs and simulation sickness
Moving around in a VR environment is different than in normal gaming. After only a few minutes, some users will get sick to varying degrees when exploring the virtual worlds. Others, on the other hand, will not be afflicted by nausea at all  . The user is visually closed off from his surroundings when using a head-mounted display (HMD). Instead, he visually experiences the rendered virtual environment. Although the images being displayed are convincing enough to give the sensation of locomotion, the body is in fact stationary. There is a discrepancy between the visual input and the other sensory information that the body receives, which leads to simulator sickness. A somewhat similar phenomenon to this is the motion sickness in cars that some people feel .
Although the feeling of nausea can come quickly, when using a HMD, users generally seem to be able to increase the time they are able to use it without feeling sick – in what is called “growing the VR legs”. This is achieved by persisting with the VR game or VR experience that the user got nausea, but doing so in small bits of time, for a while, until he can eventually sit for a long time without getting sick. This way, the maximum amount of sickness felt will get lower with time, even if at first the user might feel that he will never be able to acclimate to the VR .
In online forums, users of VR devices have been sharing their experiences with different VR games and recommendations about how to decrease the simulator sickness, and get their virtual reality legs. Some users advise not to prolong the playtime until the feeling of nausea becomes too uncomfortable. They recommend staying in the virtual environment just a bit after disorientation starts, in order to develop adaptation. Beyond that, a break is suggested. Other tips include ginger tea, or peppermint tea, to help with the nausea. Besides this, it is advised that the users adjust the settings of the device and software, like checking if the head tracking is working properly, and if the frames per second (FPS) are good enough for a smooth experience. While some users got their VR legs two weeks after starting using VR devices, others needed a month, or even 5 or 6. This adaptation led to an increase of time spent playing without noticeable side effects. It is also of notice that for different players, games might affect them differently. Also, there are some reports that getting the VR legs isn’t something permanent, with the VR sickness sensitivity increasing in direct relation to the period of time without using the VR equipment  .
Since VR sickness and adaptation is a young phenomenon, there isn’t a general consensus about how long does it take to most people to acclimate to VR. It is expected that, as VR technology progresses, these problems will be surpassed, since a user should not have any period of sickness in which he has to persist to eventually adapt to the experience .
Techniques to improve VR movement
Due to the nature of VR, walking and running often isn’t as comfortable as driving and flying. Movement is an essential part of games and game design, but it has been a challenge to fully overcome the problems of moving in a virtual environment while the body of the user stays still. Due to this, developers have experimented with new locomotion techniques, such has the method of “blinking” from one place to another. Although it is comfortable, this specific method is not the most immersive one . Other techniques are being explored and applied so the user can feel immersed in the virtual experience and not be nauseous with its exploration, although there isn’t a global solution for locomotion in VR games. While devices like the omni-directional treadmill Virtuix Omni, or VR parks such as The VOID give a good immersive experience, reducing the sickness side effects, these technologies are still not completely accessible to the average user .
One technique is roomscale locomotion, in which the user moves around within a large-scale tracking volume. Oculus and Sony already offer large-scale tracking volumes, but are focusing on a balance between standing and seated gameplay. Another one is to use a vehicle that allows the user to assume a natural sitting position while also reducing the discrepancy between what is seen to what is felt. These cockpits are used in racing or flying games, for example. It’s also possible to use a full vehicle instead of only the cockpit, provided there’s enough space available. As an example, the 2016 title Hover Junkers, by StressLevelZero, is a VR game that allows users to play with the game’s hover boats, as a roomscale vehicle . Teleportation is a technique that addresses some things that induce nausea in VR, like the Yaw stick poison, or when using the right stick of the controller to turn the POV. According to an article in uploadvr.com “YAW refers to movement along a vertical axis, such as turning the nose of an aircraft. YAW is also one of the quickest ways to get someone sick in VR. When you connect a game’s YAW control to a stick, rather than to your head motion, it creates an uncomfortable disconnect that Oculus’ CTO John Carmack has gone as far as to call “VR poison.” The teleportation method has been used to excellent effect in several virtual spaces like AtlspaceVR, or Cloudhead’s Blink, and the game Budget Cuts uses it as a gameplay mechanic  . Flight in VR has been proven to reduce the discomfort of the users, providing the ability to simulate smooth, gaze-based forward motion without dizziness. An example of this is Ubisoft’s game Eagle Flight, which attempts to provide intense action while also remaining comfortable to use. VR comfort mode makes use of a sort of micro-teleportation in which the smooth movement made with the controller’s right stick is replaced with a “snap-to” turn. This allows for a more pleasant experience in virtual reality while in a seated position. There’s also the possibility of using gaze-based locomotion in VR comfort mode, but it’s less natural than “snap-to” turns. Finally, there’s floating head, which is a VR third-person viewpoint. This method allows for good VR gameplay without the locomotion problems that first-person titles have. It’s a good way for VR newcomers to play something more familiar with traditional games and ease the transition into the new format .
As a final example, the studio Huge Robot created the Freedom Locomotion System to try to resolve the problem of comfortable and immersive VR locomotion. It is a locomotion package that comes close to solving the issue of VR locomotion with the current practical limitations of VR. This system as what has been called CAOTS (Controller Assisted On the Spot) movement, which is a sort of “run-in-place” movement system. According to George Kong, Huge Robot’s Director, “it lets players comfortably and immersively move while leaving their hands free for interactions with the virtual world (especially important for games where you might regularly wield a weapon like a gun or sword).” Besides CAOTS, the system has other subsystems that offer different modes of locomotion and methods of interaction with the virtual world .
The realization of these and other technologies or methods to reduce the problem of nausea induced by locomotion in VR will, inevitably, shorten the time in which a user gets his VR legs, until the problem is fully surpassed and the necessity to acquire the VR legs is eliminated.
- Urban Dictionary. VR Legs. Retrieved from http://www.urbandictionary.com/define.php?term=VR%20Legs
- Silicon Valley Dictionary. VR Legs. Retrieved from http://svdictionary.com/words/vr-legs
- Hayden, S. (2016). 7 ways to move users around in VR without making them sick. Retrieved from http://www.roadtovr.com/7-ways-move-users-around-vr-without-making-sick/
- Aronsson, A. (2014) Simulator sickness and VR legs. Retrieved from http://andreasaronsson.com/2014/08/18/simulator-sickness-and-vr-legs/
- Oculus Discussion Forums (2016). How long did it take you to get your “VR legs”? Retrieved from https://forums.oculus.com/vip/discussion/36541/how-long-did-it-take-you-to-get-your-vr-legs
- Oculus Discussion Forums (2015). Got my VR legs. Retrieved from https://forums.oculus.com/community/discussion/24704/got-my-vr-legs
- VR Talk (2016). How long to get VR legs? Retrieved from http://vrtalk.com/forum/showthread.php?2327-HowLong-to-Get-VR-Legs
- Lang, B. (2017). “Freedom Locomotion System” is a comprehensive package for VR movement. Retrieved from http://www.roadtovr.com/freedom-locomotion-system-comprehensive-package-vr-movement/
- Mason, W. (2015). Five ways to reduce motion sickness in VR. Retrieved from http://uploadvr.com/five-ways-to-reduce-motion-sickness-in-vr/