Wheelchair Propulsion to Reduce the Risk of Injury and Improve Propulsion Efficiency

Principal Investigator: Jeffrey R. Basford, M.D.
Project Coordinator: Brian Kotajarvi — kotajarvi.brian@mayo.edu

Figure 1: Wheelchair dynamometer with monitor for visual feedback on velocity, power output, and the fraction of effective force.

Upper extremity pain and injury are common among manual wheelchair users. This may be due in some part to inefficient stroke mechanics. Proper technique may play a role in the reduction of upper extremity dysfunction. This study investigated the effect of visual biofeedback on wheelchair propulsion efficiency by coupling the output of an instrumented wheelchair wheel to a video display and studying subjects as they propelled on a dynamometer (Fig. 1). Our goal was to assess whether subjects would be able to improve the "effectiveness" of their propulsion as measured by the fraction of effective force (FEF) which is the ratio of tangential to total force applied to the wheelchair pushrim. Our hypothesis was that providing visual biofeedback on the FEF would result in a statistically significant increase in the subject's efficiency of propulsion. A convenience sample of 16 healthy men and 2 healthy women with T4-L2 traumatic paraplegia, a mean age of 38+/-9 years, and a mean duration of manual wheelchair-based mobility of 14+/-8 years were recruited to participate in the study. Propulsion was assessed as the subjects propelled an instrumented wheelchair (with and without visual biofeedback) on a custom-built dynamometer at propulsion intensities of .15 and .25 W/kg. Results showed that visual feedback did not affect the FEF ratio at either of the propulsion intensities.

Propulsion during the higher intensity condition, however, was associated with a statistically significant 6% larger FEF than occurred at the lower intensity level. Visual biofeedback may have little utility in refining the propulsion techniques of experienced wheelchair users. A review of the literature suggests that this conclusion can be extended to novice wheelchair users as well.