There is provided a system and method for continually monitoring the occurrence of contraction during stimulation of skeletal muscle which is employed in a cardiac assist-type system. During delivery of a periodic burst, or train of stimulus pulses, the impedance of the muscle between the electrodes through which the pulses are delivered is monitored, and evaluated to determine whether or not stimulation has been achieved. In a particular embodiment, the impedance and impedance derivative values are accumulated throughout the burst, and assessed to determine whether the impedance change corresponded to a full muscle contraction. In the event of failure to stimulate the muscle to contraction, the system can automatically adjust the pulse output parameters to achieve reliable contraction.