The FITT principle has been around for a long time and is used to help structure training programs and sessions. Your learn to for the related dot point asks you to be able to design an aerobic training session using the FITT principle. The FITT principle stands for Frequency, Intensity, Time, and Type of training. Each of these is a variable that can be adjusted in order to create a training program or sessions to target aerobic or anaerobic training.
Aerobic training is training that aims to improve an athlete’s aerobic power or VO2max. Aerobic exercise, as defined by the American College of Sports Medicine, is:
any activity that uses large muscle groups, can be maintained continuously and is rhythmic in nature.
Often the FITT principle is used as follows for aerobic training:
- Frequency – 3 or more days a week
- Intensity – 60-85% MHR
- Time – 20+ min
- Type – Aerobic
And if you are a beginner to aerobic training this is what should be followed, however, research has shown that the best improvements in aerobic power or VO2max are achieved using the following:
- Frequency – 4 times a week
- Intensity – 90-100% VO2max
- Time – 35-45 min
- Type – Aerobic interval training method[1,2]
Anaerobic training, on the other hand, can be used to focus on strength, power, muscular endurance or even size. The use of the FITT principle in relation to anaerobic training, therefore, varies depending on the focus of the session. As a general guide to, develop anaerobic fitness (targeting the anaerobic lactic acid energy system) the FITT principle uses the following:
- Frequency – 1-2 times a week
- Intensity – 80-100% MHR
- Time – 10-20 min
- Type – Anaerobic interval training method
However, the data on this is very varied. Essentially you want to train somewhere around the lactate inflection point (intensity where lactic acid accumulates in the blood), and ensure you have a minimum of 48 hrs rest between training sessions. For further information on the applying the FITT principle to the various types of training, see the table here developed by ptdirect.com.
 Wenger HA, Bell GJ. “The interactions of intensity, frequency and duration of exercise training in altering cardiorespiratory fitness.” Sports Med. 1986 Sep-Oct;3(5):346-56.
 Helgerud, Jan et al. “Aerobic High-Intensity Intervals Improve V˙ O2max More Than Moderate Training.” Medicine & Science in Sports & Exercise. 2007:665-671
Training to Improve the Big Three. http://faculty.washington.edu/crowther/Misc/RBC/model2.shtml