An Improved Lever Drive Wheelchair Transmission-Phase II

Principal Investigator:  Michael L. Boninger, MD

Co Investigator: Rory Cooper, PhD

2002-2004

While the traditional wheelchair design, employing pushrims for propulsion, is simple and reliable, it is unfortunately inefficient and injurious.  Research conducted at HERL has shown that only about half of the force being applied to the pushrim produces useful torque.  A lever drive wheelchair transmission has the potential to reduce all of the risk factors for wrist and shoulder injuries.  In Phase I, a lever drive with a mechanical efficiency of over 90% has been demonstrated.  The improvement in propulsion efficiency, coupled with the improved biomechanics of the lever drive, could substantially reduce new wrist and shoulder injuries, ameliorate existing injuries and allow some individuals the option of continuing to use a manual wheelchair.  In this Phase II program, we continued the engineering development of the lever drive transmission begun in Phase I. The new device now has shift-on-the-fly capability and dynamic breaking.  In Phase II, metabolic and activities of daily living testing were also completed on thirteen unimpaired subjects.  Initial analyses revealed that the subjects used fewer strokes to propel the lever drive system compared to pushrim propulsion.  Also, greater shoulder flexion and abduction angles with less internal rotation were required when using the lever drive system.  A significant increase in shoulder flexion/extension range of motion (ROM) and a decrease in both shoulder ab/adduction ROM and internal/external rotation ROM were also found with the lever drive system compared to pushrim propulsion.