The F.I.T.T. Principle is one of the foundations of exercise; it’s a set of guidelines that help you set up a workout routine to fit your goals and fitness level while helping you get the most out of your exercise program.
The FITT principle stands for:
Frequency - how often you exercise
Intensity - how hard you exercise
Time - how long you exercise for
Type - what kind of exercise you do
For Cardio Exercise: Exercise Guidelines suggest moderate exercise five days a week or intense cardio three days a week to improve your health.
For Strength Training: A program that works every body part every session should be completed 3-4days a week with a day's rest between sessions. Or a program that focuses on just one or two body parts per session, in theory you could be completed as frequently as 6days per week.
For Cardio Exercise: The general rule is to work in your target heart rate zone and focus on a variety of intensities to stimulate different energy systems.
For Strength Training: 8-10 exercises, 1-3 sets of 8-16 reps of each exercise.
Measuring Heart Rate Zones: Heart rate is measured as beats per minute (bpm). Heart rate can be monitored and measured by taking your pulse at the wrist, arm or neck. An approximation of maximum heart rate (MHR) can also be calculated as follows: MHR = 220 - age.
Target Heart Rate: For beginners a target heart rate zone of 50-70% of their maximum of heart rate is a good place to start. For example, you are 40 years old that gives you a predicted maximum heart rate of 180bpm (220 - 40). Multiply 180 by 50% and 70% and your reach a target zone of 90bpm - 126bpm.
For fitter, more advanced individuals, a target heart rate zone of 70-85% of their maximum of heart rate may be more appropriate.
For Cardio Exercise: The exercise guidelines suggest 30-60 minutes of cardio. The length is also dependent on your intensity, the harder you work, the shorter your workouts will be.
For Strength Training: This can vary; a total body workout could take up to an hour, whereas a split routine could take less time.
For Cardio Exercise: Any activity that gets your heart rate up counts as cardio - running, walking, cycling, dancing, sports, etc.
For Strength Training: This pretty much includes any exercise where you're using some type of resistance - bands, dumbbells, machines, bodyweight etc.
In conclusion; the F.I.T.T. Principle is important because it outlines how to manipulate your program to get in shape and get better results. It also helps you figure out how to change your workouts to avoid boredom, overuse injuries and weight loss plateaus.