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A new method to quantify demand on the upper extremity during manual wheelchair propulsion
Michelle B Sabick1, Brian R Kotajarvi, Kai-Nan An
1Orthopedic Biomechanics Laboratory, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. MSabick@boisestate.edu
Objective:
To use an ergonomics-based rating that characterizes both demand on, and capacity of, upper-extremity muscle groups during wheelchair propulsion to help identify the muscle groups most at risk for pain or overuse injury in a relatively demanding wheelchair propulsion task.
Design:
Case series.
Setting:
Biomechanics research laboratory.
Participants:
Sixteen manual wheelchair users with complete (American Spinal Injury Association grade A) T6-L2 paraplegia.
Interventions:
Not applicable.
Main Outcome Measures:
Internal peak joint moments required by each of the major upper-extremity muscle groups for propelling a wheelchair up a ramp; isometric strength of each of the muscle groups in positions simulating wheelchair propulsion; and wheelchair propulsion strength rating (WPSR) for each muscle group, calculated by normalizing the joint demands to their capacity.
Results:
The largest joint moment was for shoulder flexion, at 39.7+/-13.9Nm. Shoulder flexion also accounted for the peak WPSR value of 66.5%+/-20.3%. Supination and pronation movements had low peak moment requirements (3.4Nm, 5.0Nm, respectively) but high WPSR values (41%, 53%, respectively).
Conclusions:
Even a relatively benign ramp (2.9 degrees ) places a large demand on the musculature of the upper extremity, as assessed by using the WPSR to indicate muscular demand.