Physical fitness is an enigmatic concept, because everyopne has an opinion about what constitutes good physical shape. A number of concepts can influence one's idea of physical fitness, including socialization, goals, aptitudes, and mindset. In the United States, for example, we idolize football, baseball, and hockey players more than soccer players and track athletes.
Overall, physical fitness must be calibrated according to the desired application. One application of physical fitness is the tactical profession of a soldier. A deployed soldier must frequently carry between 40 to 100 pounds of gear for a 12 to 20 hour workday. Muscle-bound and extremely large soldiers struggle with this workload, as do extremely thin types. The ideal soldier body type is a fit, trim, and muscular body structure of average weight.
Functionally applicable fitness levels have a weakness, however: most job applications do not require you to be in extremely good shape. Therefore, you must take an application and introduce its goal set into your lifestyle. For example, if your goal is to live the longest and healthiest life possible, you should focus mostly on aerobic exercise and improve your eating habits. It has been repeatedly proven that those who have a great deal of execess body weight have worse cardiovascular systems and are much more susceptible to heart attack, diabetes, and other preventable health conditions.
A summarized definition of physical fitness is that which allows you to fully participate in your own life and the lives of those around you. Particularly in the United States, aerobic fitness is the underappreciated enabler. This form of fitness keeps you fit and trim, and gives you physical mobility. Placing an emphasis on weight training generally increases mass and decreases mobility, and this mass also eventually converts to fat when it stops being utilized regularly. Therefore, physical fitness is that applied set of exercises that does the best job of setting your body up for long term success.
The key to all the information above is entirely predictable: it must be applied to be worthwhile. Many individuals start out with great expectations regarding exercise, but these expectations will never come to fruition if the required work is not executed.