1. Manual wheelchair pushrim biomechanics and axle position
Michael L. Boninger, MD, Mark Baldwin, BS, Rory A. Cooper, PhD, Alicia Koontz, MS, Leighton Chan, MD, MPH 
Archives of Physical Medicine and Rehabilitation 
Volume 81, Issue 5, Pages (May 2000)
DOI: /S (00)
Copyright © 2000 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

2. Fig. 1
Axle position measurement. The markers needed for axle position measurement as well as the orientation of the measurement are shown. XPOS, the fore-and-aft position of the axle with respect to the shoulder; YPOS, the height of the wheelchair with respect to the shoulder; MP, metocarpophalyngeal.
Archives of Physical Medicine and Rehabilitation  , DOI: ( /S (00) )
Copyright © 2000 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

3. Fig. 2
The SmartWheel and Pushrim Coordinate System. The resultant force (F) is a mathematical combination of the radial force (Fr), tangential force (Ft), and the axial force (Fz). The nonplanar moment (Mp) is a mathematical combination of the moments occurring at the hub that are not in the plane of the wheel.
Archives of Physical Medicine and Rehabilitation  , DOI: ( /S (00) )
Copyright © 2000 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

4. Fig. 3
Push angle and start angle. The start angle is measured from top dead center on the wheel. The push angle is from the beginning of hand contact until the hand leaves the pushrim. These angles are determined from the third metocarpophalangeal (MP) marker.
Archives of Physical Medicine and Rehabilitation  , DOI: ( /S (00) )
Copyright © 2000 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

5. Fig. 4
Shoulder position versus push angle. The scatter plot shows the relationship between the horizontal position of the axle relative to the shoulder and the push angle at 1.8m/sec. The more negative number for axle position indicates that the axle is farther behind the shoulder. A regression line is shown (r =.43).
Archives of Physical Medicine and Rehabilitation  , DOI: ( /S (00) )
Copyright © 2000 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

6. Fig. 5
Effect of axle position on biomechanics. Biomechanical changes associated with movement of the axle (F = resultant force). The large black arrows indicate the direction of movement of the axle relative to the shoulder, and the information in the box indicates how this affects propulsion biomechanics. For example, moving the axle farther forward relative to the shoulder is associated with a decreased frequency of propulsion.
Archives of Physical Medicine and Rehabilitation  , DOI: ( /S (00) )
Copyright © 2000 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions