Improving the efficacy of electrical stimulation-induced leg cycle ergometry: an analysis based on a dynamic musculoskeletal model

To improve the design and increase the effectiveness of electrical stimulation-induced leg cycle ergometry, it is necessary to have a better understanding of the factors that influence the force production capabilities of the stimulated muscles, the ability of the muscles to produce the desired movement, and the metabolic demands of the contractions. A dynamic musculoskeletal model capable of simulating a spinal cord injured (SCI) person exercising on a stimulation-powered leg cycle ergometer was developed to explore these issues. This model was used to address the concern whether performance can be improved by changing seat configuration, the loading, or the intermuscle stimulation pattern. Performance was assessed in terms of the probability that a given SCI subject would be able to maintain a steady cadence, the relative strength required by each muscle group to pedal alone, and the estimated rate of metabolic energy utilization associated with steady-state pedaling. The authors considered the sensitivity of the model predictions to intersubject variability. Several strategies are suggested for either minimizing the strength needed to pedal, or maximizing the cardiovascular aerobic exercise