Improving manual wheelchair design

Using the arms to rotate the wheels of a wheelchair puts a great deal of strain on the body – yet this is the typical method of propulsion for manual wheelchair users.

This means that for many, the physical stress that hands and arms are subjected to when manoeuvring the wheelchair, the physical stress that hands and arms are subjected to when manoeuvring the wheelchair is a routine problem.

According to Dr. Claire Flemmer, a professor at Massey University, New Zealand,

“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. The longer a person uses the manual wheelchair, the worse it gets.”

So, Flemmer and a team at the university have developed a wheelchair design in which the user’s hands push and pull on the pushrim, rather than just pushing forward, without having to grip it. As this propulsion method uses 100% of the total arm movement it minimises wrist and shoulder problems in addition to making travelling uphill easier.

Because the chair’s gearing system allows for this movement, the user can keep their hands on the pushrim in both a standard and a run mode. Run mode prevents the chair from rolling backwards on a slope and is intended for difficult terrain or long journeys. It uses a three-gear system similar to that of a bicycle with a high gear to be used for easier terrain and the low gear is for more difficult terrain or an uphill path.

In addition, Professor Margit Gföhler and the biomechanics and rehabilitation research team at TU Wien University, Vienna, developed a drive process that uses a hand gear propulsion system. Similarly concerned with the repetitive strain placed upon manual wheelchair users, they used a biomechanical computer to analyse the motion sequences of the upper body which ascertained that a mechanical drive system driven by two hand gears was more ergonomic and gave the best motion sequence.

The rear wheels are mounted on the wheelchair’s armrests and driven through a toothed belt using the hand gears. This is more suitable for everyday use indoors as it is a more compact design. The drive technology enabled the user to achieve the same speeds as a regular wheelchair but with a sizeable reduction in effort.
Though electric power wheelchair design and technology continues to develop, the ease of use and lightness of manual wheelchairs means that continued progress in their design supports users to continue benefitting from increased comfort and better manoeuvrability too.