There are several levels of the physical state of the body. A complete beginner will have problems with the simplest forms and usually will not be able to do many repetitions in a set. After a while, when some fat is changed with the muscle tissue, things will become a bit different. More energy will be accumulated and therefore, tasks put in front of the beginner will be easily overpowered. And this should go on until a practitioner reaches the level when he or she thinks there is not much that can be done in the specific physical activity.
And that is where they do make mistake. Usually, people try to stick to one of the several types of physical activity and take it to the maximum limit. But, the problem with muscles is, that if just one type of workout has been used, then the muscles get used to that activity and at one point, it might seem that performing of those exercises is easy. At that point, some cross training might be needed. Cardio workout is crossed with muscle mass building, but there is also one interesting type of workout and those exercises are called plyometric training exercises.
Plyometric abilities are all about increasing the explosive power as much as possible. And that is done on the mechanism that enhances our ability to perform an exercise as powerful as possible, as fast as possible. This type of exercises includes forms for both upper and lower body. Lower forms are very interesting and include an entire set of different jumping exercises (death jumps, lower jumps etc.). But some things have to be emphasized. For example, plyometric should not be done whenever a practitioner wants to do it; it is not recommendable to do plyometric workout only a day after intensive heavy lifting session. Also, there must not be more than two or three training sessions in a week, which partially creates a problem, especially if this is the supplemental type of workout and is only complementing another type of workout, which is a dominant one (with 3 or 4 rounds).
Other things to consider
When exercising, things like dieting should become very important and obviously very healthy, with the numbers of calories just enough for a fat burning process to start but not low enough to be unhealthy. Some supplements can be used in order to enhance your physical condition further.