Harmful Health Effects with Gestural Communication in VR
Despite offering a greater sense of immersion, VR experiences can cause a number of harmful health effects that also potentially prevent VR from getting mainstream adoption.
I have previously done some exploration on Motion sickness in VR, and after running a few usability studies, in this post, decided to look closer into potential adverse health effects that can be caused by offering gestural communication as the main interaction method.
These can be the result of various causes like holding unnatural poses and gestures, or copying movements that last over an extended period of time.
“Gorilla arm” syndrome
“Gorilla arm” syndrome is a discomfort or fatigue in arm(s) caused as a result of extended use of gestural interfaces without the ability of the user to rest their arm(s). [Wikipedia]
It is natural for us to rest our arms in most of our daily activities. With gestural commands in VR, there is a great risk of making users engage their arms at longer periods of time, not allowing them to rest their arms on physical objects.
“Gorilla arm” syndrome can start occurring within as little as 10 seconds of having to hold the hand(s) up above the waist in front of the user [Jason Jerald]. Thus, it is important to design experiences where interactions do not require the hands to be high and in front of the user for more than a few seconds at a time.
Having done usability testing for Tvori and Masterpiece Motion VR, I have observed how “gorilla arm” syndrome was affecting the participants’ experience due to holding the controllers in front of them in the air. The effect was eased by having a desk in front of the users where they could rest their arms, use one arm at a time, or shaking off hands from time to time.
Repetitive strain injury
Repetitive strain injury is an injury to part of the musculoskeletal or nervous system which is caused by repetitive use, vibrations, compression or long periods in a fixed position [NHS].
Cubital tunnel syndrome and carpal tunnel syndrome are the most commonly occurring RSI, with some types that with the raise of new tech have been often referred to as “text claw”, “smartphone elbow”, “Wii elbow”, “mouse arm disease”, “PlayStation thumb”, “stylus finger”, “raver’s wrist”, “Emacs pinky”, etc.
Such injuries often appear to be the result of using input devices that require continual repetitive movements, such as mice, gamepads, or keyboards.
Gestural communication can potentially enhance the already existing RSI or even cause new types of RSI. When designing VR interfaces, we have to address these potential issues, and be careful not to recreate 2D interactions that can cause repetitive strains into 3D environments.
Arm and hand injuries
Due to not being able to see the real-world environment, hand and arm injuries can easily occur — especially if the user is using gestural communication with their bare hands, and aren’t protected with the controllers in their hands.
When designing VR experience, we should consider potential arm span as well as design for rapid arm movements.
When approaching the edge of tracking, a visual, haptic, auditory warning grid should be displayed for the user to know they are approaching the edge of the safe zone.
Measuring adverse health effects
To best assess adverse health effects in VR experiences with gestural communication, we should alway run studies with observations and questionnaires before and after the experience.
To measure physical fatigue and discomfort, I have previously used a technique similar to Kennedy Simulator Sickness Questionnaire, where I first collected various user reported outcomes as a result of going through different VR experiences. I then ran studies, where I collected answers to a physical discomfort questionnaire before and after the experience, and compared the outcomes between all the users.
Such questionnaire helped me to easily spot patterns in users’ responses, and assess what types of physical discomfort caused issues in user experience.
Even though the issues observed and recorded above related to controllers input interactions, I can see those happening and evolving with gestural communication in VR too. It is also possible that with a higher mass adoption of gestural interfaces, other issues may arise on top of those.
This naturally leads me to a conclusion — design with your user in mind, test with your users, iterate based on the testing and observations :)
Are you measuring physical discomfort when building your VR experiences? Have you observed any issues when designing for gestures? Let me know in comments :)
