Influence of volitional contraction on muscle response to functional electrical stimulation

This paper focuses on the volitional contraction's impact on Functional Electrical Stimulation (FES). Hammerstein model, which combines static nonlinearity, isometric response curve (IRC), and dynamical linearity, is a common model to present the muscle response to electrical stimulation. We utilized the responses to a pseudo-random binary sequence (PRBS) excitation to identify the static nonlinearity. Then, ramp deconvolution method was used to obtain the dynamical linearity in different volitional contraction levels. Five able-bodied subjects' flexor carpi ulnaris in isometric contraction were tested. Finally, we find normalized dynamical linearity nearly remains unchanged as the volitional contraction changes. And the dead zone and saturation zone of IRC increases accompanying the bigger volitional contraction, while the linearity zone decreases. So, it is suitable to reduce the adjustable electrical stimulation intensity's scope.