Designing and implementing a personal fitness program takes time and planning. Each personal fitness program should include a warm-up, stretching, a workout, and a cool-down. The workout portion should include the principles of the F.I.T.T. formula and should consume the largest amount of time. In addition to the F.I.T.T. formula, three principles that maximize the benefits of your workout are overload, progression, and specificity. These three principles help improve your body’s cardiovascular, respiratory, and muscular systems when used properly during exercise.