Zhan Zhuang or an Internal Qigong practice is different from physical Exercises in that both mind and body are trained simultaneously as an integrated wholeness.
Training of the body by internal qigong is different from ordinary physical exercise because it is based on the training of mind while body is trained in an relaxed state. This relaxed state of the body is very important for entering an subconscious realm of mind.
Internal Qigong (including internal martial arts) is different from non-qigong exercises (including external martial arts) in that all common physical methods require you to be fully conscious, while in internal qigong you enter a state between consciousness and unconsciousness. In internal martial arts you train consciously while you are in touch with the subconscious and then you succeed unconsciously. During standing and moving mediation you imprint on your subconsciousness the fighting techniques. In fact, this subconscious is not exactly the psychological subconsciousness but includes body consciousness.
In such a relaxed state, also the healing qi (bio-electricity) runs freely inside the body, self regulates the physiological functions of the body.
Zhan Zhuang is ideal because it lowers energy consumption including oxygen consumption, blood consumption and calorie burning, etc. Thus, the body is in a state which is highly energy conserving and this accumulated energy can be used to heal many physical problems.
By doing Zhan Zhuang we use the body as much as it is needed without running out of energy. The living things have an intrinsic biological mechanism which evolves by using and degenerates by not using.
The training of the body through Zhan Zhuang has the effect of lowering energy consumption and while the body consumes less energy then energy storage will automatically increase.
It is a perfect state where we produce more energy than we consume. On contrary, other physical exercises consume more energy than our body could produce and therefore you get exhausted soon.
The stored energy after during standing internal qigong can be called potential energy. By decreasing energy consumption, energy storage is increased. This energy can be transformed into kinetic energy such as Fali (power release in yiquan system) in internal martial arts or it is used for healing by body itself.
Note: In the beginning, you will get exhausted by Zhan Zhuang until you learn to use the stabilizers and relax mobilizers. The relaxation in zhan zhuang is a must for taking the benefits of internal qigong practice.