Manual wheelchair pushrim dynamics in people with multiple sclerosis

Objectives: To define differences in pushrim dynamics during manual wheelchair propulsion by users with multiple sclerosis (MS) relative to 2 control groups of subjects with spinal cord injury (SCI) and no disability (ND) and to investigate changes in propulsion biomechanics at different speeds and with fatigue. Design: Case-control. Setting: Biomechanics laboratory. Participants: A convenience sample of 42 people, 8 women and 6 men per group. Interventions: Not applicable. Main Outcome Measures: The propulsion pattern, mean maximum speed, percentage of time in push and recovery phases, push angle, push frequency, mean maximum resultant pushrim force, mean work and push cycle, and hand-to-pushrim coupling and decoupling effects. Results: The MS groups tended to use an arcing propulsion pattern more than did the control groups (Pmax=.003). The MS group pushed at a lower mean maximum velocity (v) when allowed to choose the speed of propulsion (nu(MS), .67+/-.20m/s; nu(SCI), 1.10+/-0.23m/s: P=.001), when asked to push at 1m/s (nu(MS), .91+/-.26m/s; nu(SCI), 1.12+/-0.11m/s; nu(ND), 1.05+/-0.13m/s; P=.010). and were unable to maintain a self-selected speed during a 5-minute trial (Deltanu(MS), .15+/-.02m/s; Deltanu(ND), .03+/-.06m/s; P<.001). The MS group spent a higher proportion of time in the push phase of propulsion (Pmax=.001). In general, the MS group had smaller push angles, but push frequencies similar to the controls. Statistically adjusted MS group pushrim forces and work per push measures varied depending on context, but in all trials the MS group displayed a braking effect when grasping and releasing the pushrim. The MS group had declines in most measures when pushing at a self-selected speed for 5 minutes. In all trials, the MS group was more likely to display asymmetry between right and left sides in biomechanic parameters. Conclusions: Manual wheelchair users with MS have difficulty grasping and releasing the pushrim and maintaining speed during a fatigue trial. This likely leads to a slow self-selected speed of propulsion that may not be functional. Clinicians should remember these results when prescribing manual wheelchairs for people with MS.