Let’s say you need to clean a surface. You wouldn’t scrub the whole thing if there was just one part that was really dirty. You would concentrate on that one part. Another time, there may be just some light dust on it and in that case you would uniformly dust the whole thing.
Similarly, if you are exercising to improve your health, you wouldn’t want to do the same routine every time. You would want to diagnose what you need to work on and then target that area with an exercise that is appropriate for its condition.
Ba Gua and other Kung Fu styles, use low body stances to develop the legs. In Ba Gua there are 8 stances and together they cover every angle of every joint in the legs.
A few of them are shown below.
A practitioner who goes through all of them may identify that one of the stances is weaker than others. He could then spend more time on that one to bring all of them into balance. If the problem is flexibility he may perform some slow gentle movements to stretch and lengthen the connective tissues that prevent full range of motion in order to relax that area and improve circulation. If the issue is strength he may do a very different exercise like jumping from and into that stance.
Ba Gua also has a similar approach to the upper body with 8 animal upper body postures. These are shown below.
There are many other exercises, each one with a very specific purpose and target.
All of us have a limited time that we can afford to spend on exercise. To make the most of it, your exercise program must allow you to focus on what you need for your current condition.