Effects of Intramuscular Trunk Stimulation on Manual Wheelchair Propulsion Mechanics in 6 Subjects With Spinal Cord Injury

Abstract Objective To quantify the effects of stabilizing the paralyzed trunk and pelvis with electrical stimulation on manual wheelchair propulsion. Design Single-subject design case series with subjects acting as their own concurrent controls. Setting Hospital-based clinical biomechanics laboratory. Participants Individuals (N=6; 4 men, 2 women; mean age ± SD, 46±10.8y) who were long-time users (6.1±3.9y) of implanted neuroprostheses for lower extremity function and had chronic (8.6±2.8y) midcervical- or thoracic-level injuries (C6-T10). Interventions Continuous low-level stimulation to the hip (gluteus maximus, posterior adductor, or hamstrings) and trunk extensor (lumbar erector spinae and/or quadratus lumborum) muscles with implanted intramuscular electrodes. Main Outcome Measures Pushrim kinetics (peak resultant force, fraction effective force), kinematics (cadence, stroke length, maximum forward lean), and peak shoulder moment at preferred speed over 10-m level surface; speed, pushrim kinetics, and subjective ratings of effort for level 100-m sprints and up a 30.5-m ramp of approximately 5% grade. Results Three of 5 subjects demonstrated reduced peak resultant pushrim forces ( P ≤.014) and improved efficiency ( P ≤.048) with stimulation during self-paced level propulsion. Peak sagittal shoulder moment remained unchanged in 3 subjects and increased in 2 others ( P