The purpose of this paper was to clarify the effects of periodic execution of physical activity for female students who attended a physical education class in aerobics once a week. We investigated following matters. 1) The level of intensity students experienced during exercise. 2) The effect of exercise on the physical and mental fitness of students. Exercise intensity was the number of steps students took during periods of activity. For purpose of fitness measurement, the Health-related physical fitness test (HRPF test) ,  which includes the factor of body composition, cardiovascular endurance, flexibility, muscle power, and muscular endurance, was used as a physical resource; and Health check was used as a mental resource. As a result, a significant change in measurement values of the HRPF test was not observed up to a period of 6 months. Therefore it can be considered that the execution of physical exercise in a once-a-week class did not demonstrate a direct effect though the level of physical intensity was sufficient. However, t he fact remains that exercise undertaken as participation in class is important for the student who otherwise engages in little physical activity. Furthermore, it is necessary to consider total fitness, including both physical and mental elements.