With arms churning, shoulders lurching, and wrists twisting for the essential grip on the handrim, it’s easy to see why manual wheelchair users have high rates of carpal tunnel syndrome and shoulder injuries. Only it’s not so easy to see.

Manual wheelchair users can propel their wheels hundreds of rotations just to ambulate along a city block, and sometimes quite rapidly when it comes to, for example, crossing a busy street – a fact that makes measuring those movements difficult. It’s a challenge that is being answered by Beckman Institute faculty member Jacob Sosnoff.  

Thanks to the Americans with Disabilities Act (ADA) and a societal change in how they are viewed, people in wheelchairs have greater access to buildings, educational opportunities, and many other things life has to offer than they did 20 or even 10 years ago. What they haven’t had is science that takes a detailed look at the motion required to propel a manual wheelchair.

Sosnoff is changing that. Last year, he set up an experiment that used the motion capture suite at Beckman’s Illinois Simulator Laboratory (ISL) to glean information on the repetitive movements of manual wheelchair users in a way that’s never been done before.

The motion capture technology is the same as that used to create digital movie characters like Gollum from Lord of the Rings. Markers placed at certain points of the body were recorded by the suite’s ten cameras that can capture images at thousands of frames per second; the digital information from those points is then turned into a finely detailed graphic representation of a wheelchair user’s propulsion motion in the form of hundreds of digital, overlapping ellipses.

“An observer in real time can’t see motion irregularities and the reason you can’t see them is that it happens only once in maybe a hundred revolutions and involves very subtle variances in motion,” ISL director Hank Kaczmarski said. “Our motion capture system is capturing images at a thousand frames a second; researchers can then take the data offline and parse out these subtle differences.”

The initial focus of this project was to see if the technology and experimental set-up in the motion capture suite were effective. The answer was yes, and the results included a finding that showed differences in the propulsion patterns of experienced and novice wheelchair users.

Sosnoff, who is an Assistant Professor in the Department of Kinesiology and Community Health at the University of Illinois, collaborated on the wheelchair propulsion study with Elizabeth Hsiao-Wecksler from the Department of Mechanical Science and Engineering. A member of Beckman’s Human Perception and Performance group, Sosnoff’s research interests include aging, disability, mobility, and perceptual-motor variability.

“Predominately I’m trying to understand how we control our movements, literally how our brain controls our movements,” Sosnoff said. “I come from a behavioral standpoint. I look at behaviors to try and understand how we move, and within that I am very interested in motor variability.”

Sosnoff said that every time people do a common or repetitive movement, such as writing their name, each time there are slight fluctuations in that movement.

“What I’ve been looking at most recently is to try and see if those fluctuations in the movement, from fine movements like writing, to more complex movements like wheelchair propulsion, and see if that variability is indicative of some dysfunction,” Sosnoff said. “The analogy I like to give, especially for the wheelchair work, is that the amount of variability we see in movement can be related to muscular-skeletal pain. The idea with the study I’m doing at ISL is to see if variability in wheelchair propulsion is related to shoulder pain.”