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Fay BT, Boninger ML, Fitzgerald SG, Souza AL, Cooper RA, Koontz AM. Manual wheelchair pushrim dynamics in people with multiple sclerosis. Arch Phys Med Rehabil 2004;85:935–42. 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 ( P max=.003). The MS group pushed at a lower mean maximum velocity ( v ) when allowed to choose the speed of propulsion ( v MS , .67±.20m/s; v SCI , 1.10±0.23m/s; P =.001), when asked to push at 1m/s ( v MS , .91±.26m/s; v SCI , 1.12±0.11m/s; v ND , 1.05±0.13m/s; P =.010), and were unable to maintain a self-selected speed during a 5-minute trial (Δ v MS , .15±.02m/s; Δ v ND , .03±.06m/s; P P max=.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.

Descriptions of shoulder kinematics during wheelchair propulsion are limited to motions of the upper arm due to the difficulty of measuring scapular movement in vivo. Using a digitizing stylus, the three-dimensional positions of three anatomical landmarks on the scapula were recorded for 10 manual wheelchair users in six different statically held hand positions (−30°, −15°, 0°, 15°, 30°, 60°) on the pushrim. In each hand position, a motion analysis system recorded the coordinates of infrared markers on the arm and torso. Scapular, humeral, and torso angles were computed using an Euler angle decomposition method for each position relative to the torso. At the beginning of the push, the scapula was rotated slightly upward (1.5°), minimally protracted (15°), and maximally tipped forward (22°). In addition, the humerus was maximally extended, abducted and internally rotated. As subjects moved forward along the pushrim, the protraction angle increased while the forward tipping angle decreased. The humerus became increasingly more flexed as the push progressed with small changes observed in humeral abduction and internal rotation. A stepwise multiple regression analysis procedure (p Relevance to industry The shoulder is a common site of musculoskeletal pain and disorders among workers in occupations requiring repetitive or strenuous use of the upper arms (e.g., landscaping, construction, or textile processing). Identifying awkward or harmful shoulder postures during a task is difficult due to the inability to fully describe the dynamic movements of the various bones of the shoulder complex. This study provides a method for characterizing position of the scapula during a forceful repetitive task (wheelchair propulsion).

Fatigue is a major concern for individuals with multiple sclerosis as it interferes with daily tasks. This study compared the fatigue experienced by nine individuals with MS to nine unimpaired controls while completing a five-minute trial of continuous wheelchair propulsion. Fatigue was quantified via changes in resultant pushrim force, rate of force rise, force efficiency, axle moment and mean power frequency of the shoulder muscles. Results show a drop in the rate of rise of pushrim force that may be related to fatigue of the biceps brachii. However, given the lack of more conclusive findings and verbal reports of extreme fatigue from case subject at the end of the trial, future consideration of fatigue in MS may need to take a central versus peripheral perspective.

This study compared wrist kinematics during manual wheelchair propulsion (MWP) for 22 experienced Manual Wheelchair Users (MWU) with and without evidence of median mononeuropathy (MMN), an indicator of CTS. Thirteen (13) MWUs tested positive for MMN. Analysis found significantly higher peak wrist flexion for MWU who demonstrated CTS via the nerve conduction study. It may be prudent to instruct MWUs to avoid extremes of wrist extension.

The electromyographic (EMG) activity of forearm muscles and pushrim forces were compared between a standard and an ergonomic wheelchair pushrim for a group of non-impaired subjects propelling at two and four miles per hour. The maximum EMG signals were not statistically different for any of the muscles between rims while significantly higher peak tangential, radial, and resultant forces were found for the ergonomic pushrims.

Wheelchair users are at an increased risk for developing carpal tunnel syndrome (CTS). The objective of this study was to use electromyography (EMG) to describe wrist flexor activity (WFA) during wheelchair propulsion. EMG data on 3 flexor muscles for one subject were collected while he propelled at a constant speed of 0.9 m/s (2 mph). The flexor carpi radialis was the most active flexor muscle during the push phase with peak and average EMG at 51% and 33% of its maximum isometric contraction value.

Due to the dynamic nature of MWP, motion analysis via markers placed on bony prominences provides the best approximation of the three dimensional trajectory of the segments of the upper extremity. Previous models which use motion analysis markers have been described in the literature, but these models have not corrected for positioning of the hand in a non-neutral position. The current model provides a standard method for determining the three ranges of motion commonly attributed to the wrist: flexion/extension, radial/ulnar deviation, and pronation/supination. These quantities are calculated via a local coordinate system based at the wrist as described by Shimada (1997), but applies a correction factor to account for non-neutral hand position during calibration.

Boninger ML, Souza AL, Cooper RA, Fitzgerald SG, Koontz AM, Fay BT. Propulsion patterns and pushrim biomechanics in manual wheelchair propulsion. Arch Phys Med Rehabil 2002;83:718-23. Objectives: To classify stroke patterns of manual wheelchair users and to determine if different patterns of propulsion lead to different biomechanics. Design: Case series. Setting: Biomechanics laboratory. Participants: Thirty-eight individuals with paraplegia who use manual wheelchairs for mobility. Intervention: Subjects propelled their own wheelchair on a dynamometer at 2 different steady state speeds. Bilateral biomechanical data were obtained by using a force and moment sensing pushrim and a motion analysis system. Main Outcome Measures: The propulsive stroke of each participant for each speed and side was classified as following 1 of 4 patterns. These 4 patterns were then compared by using a mixed-model analysis of variance. The biomechanical variables that were compared were cadence, peak and rate of rise of the resultant force, mechanical effective force, push angle, and ratio of time spent pushing to time in recovery. Results: The most common propulsive stroke involved the user lifting the hand over the pushrim during the recovery phase. The stroke pattern was independent of axle position and varied from side to side and between speeds. After controlling for subject characteristics, significant differences were observed between stroke patterns in cadence and ratio of time spent pushing to time in recovery. A stroke pattern that involves using a semicircular motion with the hand below the pushrim during the recovery phase of the propulsion stroke was associated with a lower cadence and more time spent in the push phase relative to the recovery phase. Conclusion: The semicircular motion of propulsion displayed characteristics consistent with reduced repetition and more efficient propulsion. Use of this propulsion style may reduce trauma to the upper extremities. Clinicians should consider training individuals in this propulsion style. © 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation