The effect of rolling resistance on stationary wheelchair wheelies.

Objective: To test the hypotheses that increased rolling resistance (RR) reduces rear-wheel displacement and perceived difficulty during the takeoff and balance phases of stationary wheelchair wheelies. Design: We carried out within-subject comparisons of 20 participants as they each performed, in random order, two 30-sec stationary wheelies in three RR settings (tile, 5-cm-thick foam, and 12.5-cm-high blocks in front of and behind the rear wheels). The main outcome measures were rear-wheel displacement (in centimeters for the takeoff phase and centimeters per second for the balance phase) from a spring-loaded potentiometer and Likert scales of perceived difficulty. Results: For rear-wheel displacement, all six of the pairwise comparisons (three terrains X two phases (takeoff and balance)) showed a significant statistical difference (P < 0.002). In each of the six pairwise comparisons, displacement was less for the higher of the two RR conditions. For perceived difficulty, during the balance phase, participants perceived tile to be significantly more difficult than either foam (P = 0.0067) or blocks (P = 0.0002). The other pairwise comparisons were not statistically significant. Conclusion: In conditions of increased RR, rear-wheel displacement and perceived difficulty are reduced during stationary wheelchair wheelies. These findings have implications for teaching wheelchair users to perform wheelies, a foundation of many advanced wheelchair skills.