Standard wheelchair handrims are too small to provide an ergonomic grip for the hand, there is no place to rest the thumb, and there are not separate propulsion and braking surfaces. As a result, over 60% of wheelchair users grab their tire when propelling their chair. The poor fit to the hand also makes propelling less efficient and more harmful to the arms and shoulders. The Natural-Fit Handrim was designed to directly address the shortcomings of standard wheelchair handrims. The Natural-Fit (NF) has a wider surface area for the palm of the hand and a contoured area for the thumb that sits between the rim and wheel. These dual surfaces create an improved contact area for gripping the handrim, and allow for specially coated high and low friction surfaces to maximize the efficiency of propulsion and braking. After a two-week trial use period in Phase I, subjects indicated highly favorable evaluations of the NF, and propulsion biomechanics analyses indicated that the NF facilitates more efficient wheelchair propulsion. Our Phase II efforts focus on four goals: 1) Create size options for the oval component of the handrim to better customize the fit to the hand for additional target populations, particularly women and children. 2) Make design modifications to the NF to create a new model that is specifically designed for wheelchair users who have tetraplegia. 3) Test coating alternatives for the high-friction propulsion surface to optimize effectiveness and durability. 4) Examine the long-term consequences of using the NF among various populations. Extensive testing over a 4-month trial-use period will allow us to systematically test the extent to which the NF eases stress on the shoulder, wrist, and hands, and helps to reduce the likelihood of experiencing fatigue and pain as a result of daily propulsion. For the 2 million wheelchair users in the U.S. alone, the Natural-Fit will help to reduce the pain and injury associated with the repetitive stress of daily propulsion, improve quality of life, extend the time that one can remain in a manual wheelchair, and reduce medical costs associated with secondary injuries.
