Biomechanics and strength of manual wheelchair users.
OBJECTIVE
Previous investigations have identified muscular imbalance in the shoulder as a source of pain and injury in manual wheelchair users. Our aim was to determine whether a correlation exists between strength and pushrim biomechanical variables including: tangential (motive) force (Ft), radial force (Fr), axial force (Fz), total (resultant) force (FR), fraction of effective force (FEF), and cadence.


METHODS
Peak isokinetic shoulder strength (flexion [FLX], extension [EXT], abduction [ABD], adduction [ADD], internal rotation [IR], and external rotation [ER]) was tested in 22 manual wheelchair users with a BioDex system for 5 repetitions at 60 degrees/s. Subjects then propelled their own manual wheelchair at 2 speeds, 0.9 m/s (2 mph) and 1.8 m/s (4 mph), for 20 seconds, during which kinematic (OPTOTRAK) and kinetic (SMARTWHEEL) data were collected. Peak isokinetic forces in the cardinal planes were correlated with pushrim biomechanical variables.


RESULTS
All peak torque strength variables correlated significantly (P < or = 0.05) with Ft, Fr, and FR, but were not significantly correlated with Fz, FEF, or cadence. Finally, there were no relationships found between muscle strength ratios (for example, FLX/EXT) and Ft, Fr, FR, Fz, or FEF.


CONCLUSIONS
There was a correlation between strength and force imparted to the pushrim among wheelchair users; however, there was no correlation found in wheelchair propulsion or muscle imbalance. Clinicians should be aware of this, and approach strength training and training in wheelchair propulsion techniques separately.
Ambrosio
Fabrisia
F
Department of Rehabilitation Science and Technology, University of Pittsburgh, Pennsylvania, USA.
Boninger
Michael L
ML
Souza
Aaron L
AL
Fitzgerald
Shirley G
SG
Koontz
Alicia M
AM
Cooper
Rory A
RA
D000328:Adult; D001696:Biomechanical Phenomena; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000293:injuries / Q000502:physiology* / Q000503:physiopathology*; D012782:Shoulder / Q000503:physiopathology; D020069:Shoulder Pain / Q000209:etiology; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D019415:Torque; D014910:Wheelchairs