A nude model should not be instructed merely to "relax", because physical relaxation would render the model as inanimate as a subject for a still life. In fact, a nude model cannot really be instructed to do anything. The model should, of his or her own, exude enough tension to project character, contained emotion, and his or her entire life history in that single moment of nakedness. Otherwise he or she will simply look like a prostitute temporarily picked off the street.