Should I follow the FITT principle for exercise?

Starting -- or revitalizing -- an exercise program can feel like a big task. First, start where you are most comfortable. Select exercises in consultation with your physician that you enjoy and that are appropriate given your health history. Then use the acronym FITT for an easy way to remember how to continually adjust your exercise to improve your fitness. By slightly altering the Frequency, Intensity, Time (duration), and Type of exercise you do, as you are able, you will be on your way to getting fit!

Yes the FITT principle which stands for Frequency, Intensity, Type, and Time, should dictate your planning for all workouts you perform. By manipulating how many days a week you work out, how hard, what types of workouts you perform and for how long, you can improve fitness and decrease the risk of over training. If you perform the exact same workout,  at the same intensity for the same of length of time, the same days of the week, this will lead to boredom, over training, lack of progress and possibly injury.  Always strive for variety in your programs to decrease the risk of injury, and boredom, and to continue to see improvements.