Methods for estimating isometric recruitment curves of electrically stimulated muscle

Three 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. A 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.