For many wheelchair users, a common problem is the physical stress that hands and arms are subjected to when manoeuvring the wheelchair. Obviously, using arms to rotate the wheels puts a great deal of strain on the body – and yet it’s the typical propulsion method for wheelchair users.Dr. Claire Flemmer, a professor at the School of Engineering and Advanced Technology at Massey University, New Zealand, describes the pressure this puts on the wheelchair user:
“Manual wheelchairs require an inefficient push effort where the user grips either the wheel or a slightly smaller rim on the outside – called the pushrim – and propels the chair forward by pushing the rim until they are forced let go and repeat the action. This means only about 25% of the action actually contributes to the chair going forward.”
“This method causes an imbalanced repetitive strain on the shoulders and wrists that can lead to chronic pain,” she continues. “The longer a person uses the manual wheelchair, the worse it gets.”
So, Flemmer and the team at Massey have come up with Ezy-Wheels. This new wheelchair design uses a propulsion method in which the user’s hands push and pull on the pushrim, rather than just pushing forward, without having to grip it. This uses 100% of the total arm movement and consequently makes travelling uphill easier whilst minimising wrist and shoulder problems.
The chair’s gear system allows for this movement and enables the user to keep their hands on the pushrim in both a standard and a run mode. The run mode is intended for long journeys and challenging terrains and uses a three-gear system similar to a bicycle. The high gear is used for easier terrain and the low gear is for a harder or uphill path. Run mode also prevents the chair from rolling backwards on a slope.
Professor Margit Gföhler from the Institute of Engineering Design and Product Development at TU Wien University, Vienna, was similarly concerned about the repetitive strain placed upon manual wheelchair users. She and the biomechanics and rehabilitation research team at TU Wein have developed a new drive process that uses a hand gear propulsion system. By using a biomechanical computer to analyse the motion sequences of the upper body, the computer determined that a mechanical drive system driven by two hand gears gave the best motion sequence as well as being more ergonomic.
The hand gears drive the rear wheels through a toothed belt and are mounted on the wheelchair’s armrests. This enables it to be more compact, and therefore more suitable for everyday indoor use. Using the new drive technology, it was able to achieve the same speeds as a regular wheelchair but with a significant reduction effort for the user.
While we may sometimes be guilty of overlooking manual wheelchairs due to the many advancements in electric wheelchair technology, with new chair designs like these becoming more and more available, hopefully users of manual wheelchairs will gain from their improved manoeuvrability and comfort whilst still benefitting from their lightness and ease of use.
Lewis Reed Group
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