Wheelchair axle position effect on start-up propulsion performance of persons with tetraplegia.

This repeated measures study assessed the changes in speed, acceleration, stroke frequency, and shoulder range of motion (ROM) associated with different wheelchair axle positions in people with chronic cervical (C) 6 tetraplegia. Our main hypothesis is that the up and forward axle position is the most conducive to wheelchair propulsion, increasing speed and acceleration with a lower stroke frequency. In a chronic spinal cord injury (SCI) unit, we measured the speed, acceleration, stroke frequency, and shoulder ROM in four different axle positions in eight subjects with C6 SCI. We analyzed two start-up strokes over a smooth, level vinyl floor in the Motion Analysis Laboratory (Fleni Institute; Escobar, Argentina). We analyzed data for significant statistical differences using the Wilcoxon signed rank test and the Friedman test. Our study showed that the up and forward axle position results in an increase of speed and acceleration, with a higher stroke frequency and a decreased shoulder ROM. In addition, the down and backward axle position results in the lowest speed and acceleration, with a lower stroke frequency and an increased shoulder ROM. The up and forward axle position was the most conducive to stroke compared with other positions we analyzed.