Effect Of Seat Height During Manual Wheelchair Propulsion In Persons With A Spinal Cord Injury

Abstract

Seat height in manual wheelchair propulsion appears to affect submaximal physical strain and technique. In terms of efficiency an optimum seat height was described in relation to elbow angle. PURPOSE To evaluate the effect of seat height on gross mechanical efficiency (ME), metabolic strain and propulsion technique during hand rim wheelchair propulsion in subjects with a spinal cord injury (SCI) in rehabilitation. METHODS Twelve persons with SCI (8 men, 19–77yr; C5/C6-L2; 8 incomplete) conducted 8 submaximal hand rim wheelchair exercise tests at 8 seat heights (70 to 140°; full elbow extension = 180°; relative to elbow angle in a fixed sitting posture with the hands at top-dead-center of the rim). Subjects performed the tests (4min) in a counter-balanced order on a stationary computer-control led wheelchair ergometer at an individualized power output (5.4 – 13.9W; v=0.42–0.83m/s). Last minute physiological and technique data (fraction effective force [FEF], total force [Ftot], mediolateral [Fy] and vertical force [Fz] components and push time [PT]) were evaluated using a repeated measures ANOVA (P <0.05). RESULTS All physiological data – including ME – showed significant differences (P <0.05) with seat height. Visual inspection showed a tendency for ME to optimize at 100–130° with clear detrimental values at 80 and 90°. FEF decreased (71–58%) and Ftot, Fy and Fz increased significantly with increasing seat height. PT remained constant. DISCUSSION: Physiological data indicate a tendency to optimize with seat height. This trend does not seem to relate to trends in technique data, which seem to be regulated by different task or geometry-related boundary conditions. A preliminary regression analysis showed an impact of lesion level on the physiological data. Future studies must verify the impact of lesion level on seat height results. CONCLUSIONS Optimum seat height in terms of ME in SCI during rehabilitation tends towards 100–130° elbow angle. Individual seat height evaluation seems indicated during SCI rehabilitation.