When you do the same thing day after day you get very good at it. You may also become physically and mentally stale, bored and prone to injury or burnout. If you always do the same type of workout, you may eventually hit a plateau and fail to see any additional improvement. Olympic athletes use the off-season to mix it up and modify their workouts every few weeks or months. They often choose sports very different from the one in which they compete and change the intensity of exercise and the amount of rest between workouts.