Seat height in handrim wheelchair propulsion

To study the effect of seat height on the cardiorespiratory system and kinematics in handrim wheelchair ambulation, nine non-wheelchair users participated in a wheelchair exercise experiment on a motor-driven treadmill. The subjects conducted five progressive exercise tests. After an initial try-out test, four tests were performed at different standardized seat heights of 100, 120, 140, and 160 degrees elbow extension (subject sitting erect, hands on the rim in top-dead-center = 12.00 hrs; full extension = 180 degrees). Each test consisted of four 3-minute exercise blocks at speeds of respectively 0.55, 0.83, 1.11, and 1.39 m.s-1 (2-5 km.hr-1). Analysis of variance revealed significant effects of seat height (P less than 0.05) on gross mechanical efficiency (ME), oxygen cost, push range, and push duration, and on the ranges of motion in the different arm segments and trunk. Mean ME appeared higher at the lower seat heights of 100 and 120 degrees elbow extension. This is reflected in an enhanced oxygen consumption at seat heights of 140 and 160 degrees elbow extension. Simultaneously, the push range showed a 15 to 20 degree decrease with increasing seat height, which is reflected in a decreased push duration. In the push phase, decreases in retroflexion and abduction/adduction of the upper arm were seen. The trunk shifted further forward, and the motion range in the elbow joint shifted to extension with increasing seat height. No shifts in minimum and maximum angular velocities were seen with increasing seat height. The results showed an interrelationship between wheelchair seat height and both cardiorespiratory and kinematic parameters. With respect to the cardiorespiratory system, the optimization of the wheelchair geometry, based on functional characteristics of the user, appears beneficial.