Effect of backrest height on wheelchair propulsion biomechanics for level and uphill conditions.
OBJECTIVE
To evaluate the effect of backrest height on wheelchair propulsion kinematics and kinetics.


METHODS
An intervention study with repeated measures.


METHODS
University laboratory.


METHODS
Convenience sample included manual wheelchair users (N=36; 26 men and 10 women) with spinal cord injuries ranging from T8 to L2.


METHODS
Participants propelled on a motor-driven treadmill for 2 conditions (level and slope of 3°) at a constant speed of 0.9 m/s while using in turn a sling backrest fixed at 40.6 cm (16 in) high (high backrest) and a lower height set at 50% trunk length (low backrest).


METHODS
Cadence, stroke angle, peak shoulder extension angle, shoulder flexion/extension range of motion, and mechanical effective force.


RESULTS
Pushing with the low backrest height enabled greater range of shoulder motion (P<.01), increased stroke angle (P<.01), push time (P<.01), and reduced cadence (P=.01) regardless of whether the treadmill was level or sloped.


CONCLUSIONS
A lower cadence can be achieved when pushing with a lower backrest, which decreases the risk of developing upper-limb overuse related injuries. However, postural support, comfort, and other activities of daily living must also be considered when selecting a backrest height for active, long-term wheelchair users. The improvements found when using the low backrest were found regardless of slope type. Pushing uphill demanded significantly higher resultant and tangential force, torque, mechanical effective force, and cadence.
Department of Occupational Therapy, College of Health Science, Kaohsiung Medical University, Kaohsiung City, Taiwan.
Yu-Sheng
YS
Yang
Alicia M
AM
Koontz
Shan-Ju
SJ
Yeh
Jyh-Jong
JJ
Chang
D000054:Acceleration; D000222:Adaptation, Physiological; D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011597:Psychomotor Performance; D016059:Range of Motion, Articular / Q000502:physiology; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D019415:Torque; D034941:Upper Extremity / Q000502:physiology*; D014910:Wheelchairs