Methods for estimating isometric recruitment curves of electrically stimulated muscle

Four methods for estimating the recruitment curve of isometric, electrically stimulated muscle are described. Three of the methods were tested experimentally in isolated tibialis anterior and medial gastrocnemius muscles of cats. The three methods are steady-state step response, peak impulse response, and deconvolved ramp response. The fourth method, described but not tested, is a stochastic iteration technique. The results demonstrate that estimations of recruitment curves depend on the method used and that all methods are sensitive to short-term and long-term time-variations in muscle properties. While the step response technique is the traditional method for estimating recruitment curves, the ramp deconvolution method appears to offer acceptable accuracy with much shorter testing times.