Below is an overview of the 5 critical components of any sound fitness program. Commonly referred to as 'aerobic' exercise, or just 'cardio', it is still at the center of every fitness program. Cardiorespiratory exercise works the lungs and heart because it puts an increased demand on both, and in turn, the entire body adapts by becoming more efficient. By doing participating in cardiorespiratory exercise on a regular basis, the body stays efficient, and even continues to improve the function of both the heart and the lungs. On the other hand, if you discontinue cardio your body will become less efficient, because there are no longer any demands being placed on the systems.
Muscles respond to resistance training by becoming stronger, more firm, and more shapely.
In order for the muscles to improve they must be stressed, or 'overloaded' past the point of what they are accustomed to. You can overload your muscles in several different ways, depending on what equipment you have available, if any, what your goals are, and what you enjoy. It's important to include resistance training in your routine for several reasons. First, and most obvious, shapely muscles look great. You can bring your body into proportion with itself if you happen to be one of those people cursed with a thick waist, or large thighs.