Biomechanical analysis of functional electrical stimulation on trunk musculature during wheelchair propulsion.

BACKGROUND The objective of this study was to examine how surface electrical stimulation of trunk musculature influences the kinematic, kinetic, and metabolic characteristics, as well as shoulder muscle activity, during wheelchair propulsion. METHODS Eleven participants with spinal cord injury propelled their own wheelchairs on a dynamometer at a speed of 1.3 m/s for three 5-minute trials. During a propulsion trial, 1 of 3 stimulation levels (HIGH, LOW, and OFF) was randomly applied to the participant's abdominal and back muscle groups with a surface functional electrical stimulation device. Propulsion kinetics, trunk kinematics, metabolic responses, and surface electromyographic (EMG) activity of 6 shoulder muscles were collected synchronously. Kinetic, kinematic, and EMG variables were recorded during 3 time intervals (30 seconds each) within a 5-minute trial. Metabolic variables were recorded through the entire 5-minute trial. RESULTS Participants with HIGH stimulation increased their gross mechanical efficiency (P=.05) during wheelchair propulsion. No differences were found in shoulder EMG activity, energy expenditure, and trunk motion between stimulation levels. CONCLUSION Functional electrical stimulation on the trunk musculature has potential advantages in helping manual wheelchair users with spinal cord injury improve propulsion efficiency without placing additional demands on shoulder musculature.