Background: Inactivity is a major cause of cardiovascular disease and osteoporosis. Physical activity can be helpful, however little is known about the role of duration and severity of such programs on heart rate and aerobic power. We have studies the effects of8- and 16-week aerobic training program with 70 and 85% of maximum aerobic power on resting heart rate (RHR) and aerobic power. Materials and methods: Thirty healthy inactive females aged 18-33 years have entered this experimental study. Cases were assigned randomly in experiment (20) and control group (10). RHR and maximum aerobic power were determined before and after 8- and 16-week training program (thrice a week) with 55-70% and 70-85% of maximum aerobic power. Similar tests were achieved in the control group who had no exercise. Results: Having 16 weeks of aerobic exercise, RHR was reduced (71.2±4.5 vs. 65±4.6 beats/s, p<0.04). This showed a significant difference when compared to the control group (p=0.019). Meanwhile, maximum aerobic power was increased (3.57±1.6 vs. 4.25±2.1 l/min, p=0.05). Conclusion: Sixteen weeks of aerobic exercise with 70-85% of maximum aerobic power is necessary to altered RHR and maximum aerobic power in healthy inactive females. Further studies are highly recommended in other patients who are at risk of cardiovascular diseases.