The effect of mass on the kinematics of steady state wheelchair propulsion in adults and children with spinal cord injury

• Main Author: Bednarczyk, Janet H.
• Language: English
• Published: 2008
• Online Access: http://hdl.handle.net/2429/1265

A recent trend in wheelchair design has been the reduction of the mass of wheelchairs. The purpose of this study was to examine the effect of mass on the kinematics of steady state wheelchair propulsion. The mass of test chairs (9.3 kg) was manipulated by mass additions (5 and 10 kg) in two, neurologically matched, groups (n=10) of adults and children with spinal cord injury. Three dimensional video analysis was used to determine the movement of upper body angles (elbow, shoulder, trunk, and shoulder abduction). Statistical analysis were multiple univariate, repeated measures analysis of variance (ANOVA) and analysis of covariance (ANCOVA) with significance set at adjusted p values <0.05. The average mass and age of the pediatric group was much smaller than the adult group (37.4 kg and 11.3 years versus 68.5 kg and 33.5 years). The averaged group wheeling velocities were 2.26 m/sec (pediatric) and 2.38 m/sec (adult). A two-(groups)-by-four-(conditions) ANOVA of the actual wheeling velocities showed a significant groups effect and a nonsignificant interaction effect. The two groups spent comparable proportions of the wheeling cycle in propulsion (pediatric = 24.45 %, adult = 24.41 %). A two-(groups)-by-four-(conditions) ANCOVA of the % propulsion data showed that both the groups effect and the groups-by-condition interaction effect were not significantly different. A two-(groups)-by-four-(conditions)-by-six-(portion of wheeling cycle, first 25%) ANCOVA of the angular data (with velocity as the covariate) showed significant differences for three (elbow, shoulder, and shoulder abduction) of the four angular parameters and nonsignificant groups-by-conditions effects. These results, based on a test sample of chairs and subjects, indicate that mass additions did not affect the angular kinematics, % propulsion or wheeling velocities of two groups of subjects with spinal cord injury in steady state, short distance, level wheelchair propulsion. The pediatric group did show significant absolute angular differences from the adult group, but the angular changes over time and across experimental conditions were the same in both groups.