The recommendations for maintaining fitness are based on the three training principles:
The recommended frequency is three to five days per week for 30 minutes. The amount of improvement increases with frequency, but the magnitude of change is smaller and tends to plateau when frequency is increased above three days per week.
The intensity and duration of training are linked, with total volume being an important factor in improvement. Improvement will be similar for activities performed at a lower intensity/longer duration compared with higher intensity/shorter duration as lomg as the total energy used by both the activities is similar.
The intensity ranges from 55 percent to 90 percent of maximum heart rate and the duration of training ranges from 20 minutes to 60 minutes of continuous or intermittent aerobic exercise such as running, walking, cycling, swimming or an aerobics class.
However, for best overall results it is recommended that the exercise be performed at a “moderate-intensity” level.