Seat height:effects on submaximal hand rim wheelchair performance during spinal cord injury rehabilitation

OBJECTIVE: To evaluate the effects of wheelchair seat height on wheeling efficiency and technique during rehabilitation in subjects with a spinal cord injury.DESIGN: Laboratory-based study.SUBJECTS: Twelve persons with spinal cord injury (age range 19-77 years, lesion level: C5/C6-L2; 7 men; 8 incomplete).METHODS: Subjects conducted 8 submaximal hand rim wheelchair exercise tests (4 min) on a computerized ergometer at 8 seat heights (elbow angle: 70-140 degrees , full extension = 180 degrees) in a counter-balanced order (individualized fixed power output (5.4-13.9 W) and speed). Last-minute physiological and technique parameters were evaluated using repeated measures analysis of variance (ANOVA) and multilevel regression analysis (p < 0.05).RESULTS: Physical strain and mechanical efficiency changed significantly (p < 0.05) with seat height, with optimal values at 100-130 degrees . Lower seat heights were clearly detrimental. Forces on the hand rims were affected by seat height, showing lower forces with increasing seat height. Lesion level was not a confounder of seat height with respect to mechanical efficiency, oxygen uptake or fraction effective force.CONCLUSION: Mean physiological data indicate a tendency to optimize at 100-130 degrees seat height. This does not relate to the trends seen in force and technique data. Optimization of seat height during spinal cord injury rehabilitation may lead to more efficient and less straining conditions for manual wheeling.