Approaches for determining energy parameters for electrical stimulation pulses that produce a desired activation and avoid an undesirable activation are described. A strength-duration relationship for at least one desired activation produced by therapeutic electrical stimulation is measured. A strength-duration relationship for at least one undesirable activation produced by the therapeutic electrical stimulation is provided. A medical device selects, based on the desired and undesirable strength-duration relationships, one or more energy parameters for the therapeutic electrical stimulation that produce the desired activation and avoid the undesirable activation.