Any training program must take into account the specific needs and abilities of the individual for whom it is designed. No two individuals will respond in the same way to a given programme.
Training must include overload and progression to be successful. Overload is to force the body to work harder than normal so the body adapts to this given workload. Progression is to increase this work load once those adaptations have occurred. The load should be increased gradually overtime to avoid any risk of injury
What ever your goal is the supporting training programme must emphasise on that particular component to ensure the correct adaptations occur. e.g A rugby player trying to improve strength would not benefit from doing long aerobic runs.
Maximum benefits are obtained when a programme includes a variety of training methods.
For a muscle or a muscle group to develop it must have adequate rest to recover and following a session or exercise.
If a Muscle, Muscle group or energy system is not given regular progressive stimuli, then the natural effect is to lose the adaption causing a de-training effect.