The American College of Sportsmedicine recommends the above prescription in order to achieve moderate to high aerobic fitness levels. In order to achieve the benefits of regular aerobic activity, you will need to perform aerobic exercise between 3 days and 5 days per week. While some extra improvement in aerobic capacity may be realized with exercising more than 5 days per week, there is extra risk with such a program. Exercising too many days per week may lead to "overtraining" and associated overuse injuries like "shin splints" and other forms of tendinitis. Overtraining may also predispose one to illness as the immune system may become run-down and suppressed.

Twenty to 60 minutes is the recommended "duration." It takes a minimum of 20 minutes to achieve the aerobic "training effect." The appropriate "intensity" should be between 70 and 85% of your maximum heart rate (MHR). Since exercise intensity is the most difficult of the exercise prescription to measure, we will consider heart rate in some detail below.