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VR controllers are leading to ‘gorilla arm’ fatigue


Researchers have warned that radical new virtual reality technology is leading to a new wave of ailments. 

Researchers have been studying arm and muscle fatigue connected to the use of hand gestures for mid-air computer interaction, such as with Facebook’s Oculus Rift touch controllers.

They found fatigue from prolonged use of these motions can lead to ‘gorilla arm’ – when someone uses a mid-level screen or touchscreen for a long period of their time and their arm starts to hurt because of the awkward positioning that is required. 

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Arm fatigue accumulates during a prolonged use of mid-air interfaces such as Oculus Rift. But gorilla arm syndrome is already an issue with vertical touchscreens, making it a problem even beyond augmented virtual reality systems

Arm fatigue accumulates during a prolonged use of mid-air interfaces such as Oculus Rift. But gorilla arm syndrome is already an issue with vertical touchscreens, making it a problem even beyond augmented virtual reality systems

Arm fatigue accumulates during a prolonged use of mid-air interfaces such as Oculus Rift. But gorilla arm syndrome is already an issue with vertical touchscreens, making it a problem even beyond augmented virtual reality systems

The research could help user interface designers predict how fatiguing a particular interface would be, enabling them to make better design decisions. 

‘In previous years, all the computer interaction technologies we had included something to support our limbs,’ said Dr Karthik Raman, a Professor at Purdue University’s school of engineering and the lead author of the study. 

‘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.’ 

New technologies have created mid-air interaction advancements in gaming, augmented and virtual reality and mobile technologies which require the use of hands. 

Gorilla arm syndrome is already an issue with vertical touchscreens, making it a problem even beyond augmented virtual reality systems, said Dr Wolfgang Stuerzlinger, an expert on 3-D user interfaces at Simon Fraser University in Vancouver, and a co-author of the study.

HOW THEY DID IT 

The researchers conducted two experiments: One to determine a person’s arm strength, and another to estimate their cumulative fatigue levels.

The researchers used inexpensive depth cameras, which are used in home video game systems, to sense body motion and hand motion.

To measure arm strength, 20 men and four women were asked to grasp a dumbbell (five pounds for men, three pounds for women) and hold them out horizontally for as long as they could, while the camera sensors measured what their hands and arms did.

In a second experiment to measure cumulative strength, participants were shown targets on a screen and asked to touch the targets as many times as possible with good accuracy four times for one-minute segments, with random rest duration’s of five to 20 seconds between each segment.

The screen was placed at shoulder and waist-level heights, with depth cameras again used to analyze the body’s skeleton. 

‘Physical ergonomics is an important design factor for mid-air interaction,’ Dr 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.’

To conduct the study, the researchers, based at Purdue’s C Design lab, looked at the issue in two ways: Determining a person’s arm strength and estimating their cumulative fatigue levels.  

But according to Dr Ramani, current methods to measure strength are expensive and invasive and can leave out considerations for rest.

So to simplify the study and make it less costly, the researchers used inexpensive depth cameras, which are used in home video game systems, to sense body motion and hand motion. 

In a first experiment to measure arm strength, 20 men and four women were asked to grasp a dumbbell ( five pounds for men, three pounds for women) and hold them out horizontally for as long as they could, while the camera sensors measured what their hands and arms did.

Using this method, the researchers said they were able to determine arm strength with an average error risk of 8.4 per cent – 2.2 per cent higher than the 6.2 per cent error risk recorded by current, more costly methods. 

Then, in a second experiment to measure cumulative strength, participants were shown targets on a screen and asked to touch the targets as many times as possible with good accuracy four times for one-minute segments, with random rest duration’s of five to 20 seconds between each segment.

In an experiment to measure cumulative strength, participants were shown targets on a screen and asked to touch the targets as many times as possible with good accuracy four times for one-minute segments, with random rest durations of five to 20 seconds between each segment. The screen was placed at shoulder and waist-level heights, with depth cameras again used to analyze the body's skeleton. This image shows these mid-air pointing tasks, where seven circular targets are arranged on a virtual plane

In an experiment to measure cumulative strength, participants were shown targets on a screen and asked to touch the targets as many times as possible with good accuracy four times for one-minute segments, with random rest durations of five to 20 seconds between each segment. The screen was placed at shoulder and waist-level heights, with depth cameras again used to analyze the body's skeleton. This image shows these mid-air pointing tasks, where seven circular targets are arranged on a virtual plane

In an experiment to measure cumulative strength, participants were shown targets on a screen and asked to touch the targets as many times as possible with good accuracy four times for one-minute segments, with random rest durations of five to 20 seconds between each segment. The screen was placed at shoulder and waist-level heights, with depth cameras again used to analyze the body’s skeleton. This image shows these mid-air pointing tasks, where seven circular targets are arranged on a virtual plane

The screen was placed at shoulder and waist-level heights, with depth cameras again used to analyze the body’s skeleton. 

Dr Ramani says that the researchers were able to estimate cumulative fatigue at an improved error rate of 15 per cent, compared to 35 per cent with traditional methods.

‘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,’ said Dr Stuerzlinger.

The research's method could also be used to measure strength and fatigue for the aging population, as well as for continuous monitoring of fatigue levels in at-risk populations'

The research's method could also be used to measure strength and fatigue for the aging population, as well as for continuous monitoring of fatigue levels in at-risk populations'

The research’s method could also be used to measure strength and fatigue for the aging population, as well as for continuous monitoring of fatigue levels in at-risk populations’

‘This, in turn, will accelerate and lead to the development of better user interface solutions for virtual and augmented reality systems.’

The study’s method of measuring strength and fatigue could also have far-reaching implications for the aging population, said Dr Satyajit Ambike, a researcher at Purdue University’s Department of health and Kinesiology and a co-author of the study. 

‘Our inexpensive methods will potentially translate to establishing the relation between fatigue/strength and health, as well as into continuous monitoring of fatigue levels in at-risk populations,’ he said.

‘In this way, this technology promises to have a significant clinical impact.’



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