The SAID Principle (Specific Adaptation To Imposed Demands) says that your body will adapt to the specific stresses that are placed on it. You can’t expect the results of a body builder if your workout program consists of swimming, running, and eating salad. The goals that you set for yourself have to match your workouts and diet. Your body adapting to the stresses imposed upon it is not always a good thing. If you keep doing the same workouts, your body will not get as stressed because it will become used to it. That means you will not continue to see the same level of results. It is good to stress your body according to your goals, but you also want to vary the workouts. That way your body will continue to adapt and produce results.