Arm and muscle fatigue accumulates during prolonged use of mid-air computer interfaces say Purdue University researchers

Computer interaction improvements have included the expanding use of natural motions and gestures to control floating graphical user interfaces. As a result, fatigue from prolonged use of the motions and gestures have become an issue.​. 

Karthik Ramani, the Donald W. Feddersen Professor in the School of Mechanical Engineering, is part of a study to evaluate and quantify arm fatigue in a simplified framework compared to current methods.

“In previous years, all the computer interaction technologies we had included something to support our limbs,” Ramani said. “But with newer forms of interaction, there is no support. The question now is what the guidelines are to design new interfaces and interaction for such settings.”

Technology has created mid-air interaction advancements in gaming, augmented and virtual reality applications and the use of mobile technologies using hands.​​

“Physical ergonomics is an important design factor for mid-air interaction,” Ramani said. “In particular, arm fatigue – the so-called ‘gorilla arm syndrome’ – is known to negatively impact user experience and hamper prolonged use of mid-air interfaces.”

Ramani, who also has a courtesy appointment in the School of Electrical and Computer Engineering, is joined in the research by Sujin Jang, a doctoral student in the School of Mechanical Engineering, and Satyajit Ambike, an assistant professor in the Department of Health and Kinesiology, as well as Wolfgang Stuerzlinger, a professor in the School of Interactive Arts and Technology at Simon Fraser University, Vancouver, Canada.

The study looked at the issue of human-computer interaction in two ways: Determining an individual’s arm strength and estimating cumulative subjective fatigue levels.

Ramani said current methods to examine strength are expensive and invasive and can leave out considerations for rest. To simplify the issue, the study opted for inexpensive depth cameras, which are used in popular home video game systems to sense body motion and hand motion.

In the end, Ramani said the study was able to estimate the cumulating subjective fatigue at an improved 15 percent error rate over traditional methods.

According to Stuerzlinger, an expert on 3-D user interfaces, the “gorilla arm syndrome” is already an issue with vertical touchscreens, making it a problem even beyond augmented and virtual reality systems.

“The results of our work enable user interface designers to predict how fatiguing a specific user interface is, even before a new design is built/realized, which enables the designers to make better decisions around new, proposed 3-D user interfaces,” he said. “This, in turn, will accelerate and lead to the development of better user interface solutions for virtual and augmented reality systems.”

For Ambike, the study’s method of measuring strength and fatigue could have far-reaching implications for the aging population.