In order for a training program to be most effective, the hard workouts should be hard, and the easy workouts should be easy. Too often, endurance athletes spend too much time training between these two intensity extremes or they change workouts "on the fly." Frequently they do not understand the goals or reasons for each workout. Changing workouts, or allowing others to determine the intensity of a workout, can easily disrupt an individual's overall training program. Every workout should have a goal that is defined before the workout begins, and the workout should be followed as intended.