Limitations of Kinematics in the Assessment of Wheelchair Propulsion in Adults and Children With Spinal Cord Injury

Abstract

Recently, there has been a trend for designers to reduce the weight of wheelchairs. Wheelchair performance is frequently evaluated in clinical as well as laboratory settings by kinematic motion analysis. The purpose of this study was to examine the effect of weight on the kinematics of wheelchair propulsion in nonathletic adults and children with spinal cord injury. The weight of identical new low-weight test chairs (9.3 kg) was manipulated by adding weight (5 and 10 kg) in two matched groups (n = 10) of adults and children with spinal cord injury. The three-dimensional coordinates of reflective markers were obtained as the subjects performed level wheeling at a speed of 2 m/s. The pediatric group was found to have significantly lower wheeling speeds than the adult group. The addition of weight, however, did not alter the wheeling speeds in either group. Neither the proportions of the wheeling cycle spent in propulsion (24%) nor the angular (shoulder flexion-extension, elbow flexion-extension, shoulder abduction, and trunk flexion-extension) kinematics of wheeling changed with additions of weight in either group. The angular kinematics of the pediatric group, however, were different than those of the adult group. These results indicate that adding weight in the range of 5 to 10 kg did not affect wheeling style under the level-wheeling, low-speed conditions of the study. It is possible that performance in wheelchair propulsion may be more appropriately determined by kinetic and energetic outcome measures than by kinematic measures.