FlexRim Low Impact Wheelchair Pushrim 

Final Report PDF

Project Goal

The goal of this research project is to develop and evaluate a FlexRim low impact wheelchair pushrim. This innovative pushrim is designed to lower the impact forces experienced by wheelchair users during propulsion. The FlexRim reduces impact forces by replacing the rigid interface normally found between the wheelchair wheel and the pushrim with a flexible interface. When an impact load is delivered to the FlexRim during propulsion, the FlexRim is able to displace relative to the wheel and reduce the impact stresses related to upper extremity injuries.

Need for Low-Impact Pushrims

Approximately 65% of manual wheelchair users experience upper extremity pain or injury, which can significantly impact their mobility and independence. Research has demonstrated a relationship between impact stresses on the upper extremities during wheelchair propulsion and upper extremity injury. Impact stresses occur when the hand contacts the pushrim, transmitting the stresses to the wrist, elbow, and shoulder. Current pushrim technologies do not effectively reduce these impact stresses.

Phase I FlexRim Concepts

In Phase I, three FlexRim concepts were developed and evaluated to determine their effect on propulsion kinetics, wheelchair maneuverability, and mechanical efficiency. The concepts allowed the pushrim to translate relative to the wheel, thus lowering the impact forces. FlexRim prototypes that allowed translational displacement resulted in reduced impact forces and mechanical efficiencies greater than 96%. Wheelchair users preferred FlexRim prototypes with conservative force-displacement characteristics.

FlexRim Shock Mount Concept

Phase II Proposed R&D

A proposal was submitted to the National Institutes of Health in April of 1999 for Phase II funding. In Phase II, new FlexRim concepts will be developed and evaluated based upon Phase I results. Biomechanical evaluations of impact loading and mechanical efficiency will be conducted at the Pittsburgh Human Engineering Research Laboratories with 15 subjects. In addition, 30 wheelchair users will evaluate the FlexRim over a three to six month period of use. Because the FlexRim reduces impact stresses related to upper extremity injuries, it serves to prevent injury, and preserve function and mobility.


This research was co-funded by the National Institute of Child Health and Human Development and the National Center for Injury Prevention & Control (NCIPC), Centers for Disease Control and Prevention (CDC) through Small Business Innovation Research Phase I Grant # 1 R43 HD36533-01.