Virtual reality interface design affects users both physically and mentally

Once seen as a novelty, virtual reality (VR) technology has dramatically improved over the years and now is used widely in fields including health care, manufacturing and training.

To improve VR systems, researchers have focused on how the size, location and distance of VR interface elements, known as targets, affect user performance. For instance, users can interact with larger and nearer targets more quickly and effectively than those that are smaller or further away.

Until now, however, little research has investigated how these elements affect users physically.

A study by ergonomics expert Jeong Ho “Jay” Kim, PhD, with the Texas A&M University School of Public Health, and others is among the few to evaluate how target size affects user neck and shoulder biomechanics, task performance and cognitive load.

“Like computers, smart phones and other technologies, VR systems can increase the risk of eyestrain and repetitive stress injuries for users,” Kim said. “We wanted to find how VR interfaces might affect user health to help develop guidelines for their use.”

Testing VR Technology

For the study, published in Ergonomics, Kim and colleagues from Oregon State University and Northern Illinois University studied 20 adults aged 18 to 49 who had no history of neck and shoulder musculoskeletal issues or neck and shoulder pain in the past week.

The participants used a commercial, off-the-shelf VR headset with a hand tracking module to perform two tasks: pointing to circular targets arranged in a circle and coloring highlighted squares in a three-by-three grid.

Both tasks had small, medium and large targets, with small and large targets being 50 percent smaller or larger than medium targets, respectively. While participants carried out these tasks, the researchers measured neck and shoulder joint movement using a motion capture camera system and collected muscle activity data using electromyography.

Participants also answered questions regarding the mental and physical demands, effort, frustration, distress and engagement involved with each task and how long it took them to complete each task.

Findings

“We found that neck muscle activity was highest in large target tasks, likely because participants had to move their heads more to interact with the elements,” Kim said. “Similarly, participants had greater shoulder biomechanical loads, with larger degrees of movement for the large-target tasks.”

In addition, participants perceived the tasks’ mental demands as low, possibly due to their simplicity and short duration, but reported the large targets as being somewhat more demanding. Furthermore, task completion took longer with large targets than with small or medium ones.

These findings point to a potential for target size to affect VR users physically and mentally, but the researchers note a few limitations to their research. First, the tasks were short and relatively simple, making it impossible to measure effects of fatigue from long-term use. The study also focused exclusively on younger participants, meaning the findings may not apply for older users. Lastly, the study used a single VR system model.

Kim said that future research using a wider participant age range, longer duration, more complex tasks and other models of VR headset would expand on this study’s findings.

“Despite this, our study highlights the need to focus on target size and its possible influence on physical and cognitive performance when designing interfaces,” Kim said. “With a better understanding of how target size and distance can affect users, designers can reduce the risk of musculoskeletal problems, decrease cognitive load and improve user performance and experience.”

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