The treatise “On Hygiene” supplies a wealth of information about the major change in the field of athletics, which took place in the Roman imperial period, and the prevalence of athletic exercise. It notes the lack of proportionate and controlled exercise and its dangerous effects on athletes. It also pinpoints the impotence in diagnosing the physical and psychological condition of the athlete and consequently the inability in selecting for and adapting to him the proper exercises. The intellectuals of the age express the demand for redefining physical exercise, that should be connected with medicine and hygiene, and propose the application of the “art of hygiene” in gymnastics. Thus, it is strongly suggested that only the natural well-being that can be achieved through gymnastic exercises shields and reinforces health. Therefore, the participation of a professional instructor of gymnastics in exercises is indispensable: he must have sufficient knowledge of medicine and hygiene, so that he can be capable to evaluate the conventionality of bodies and exercises and to decide whether specific exercises can harm or benefit the particular individual.