Exercise intensity and fitness

Several studies have shown that in achieving aerobic fitness, exercise intensity is the most important factor? not frequency or duration. If the training intensity remains the same and the frequency and duration is reduced, aerobic performance does not decrease. On the other hand, if intensity is reduced, while duration and frequency remain unchanged, the level of aerobic fitness declines considerably. At the same time, it does not mean that in order to become physically fit a person needs to participate in extremely vigorous exercise. To reach favorable levels of fitness and weight loss maintenance, one has to exercise at a heart rate of between 75-85% of MHR, 3-5 times a week, for a period of between 20-60 minutes.