Three primary power centers exist within the body.
These are the center of vitality in the lower abdomen, the astral center at the solar plexus level and the mental center in the head.
The center of vitality is subject to constraints of mass, time and space. A frequent sensation with working with vital energy is a feeling of heaviness in the lower abdomen that can be shaped and held for a limited period of time. The infamous “chi belly” of tai chi practice is an example of this. As this energy can be shaped and contains weight it can also be utilized to accomplish physical goals of skills like fah jing (i.e. explosive discharge of force). As a near physical phenomena it has a limited lifespan as well, so it requires frequent practice to maintain.
The astral center is not subject to time. When properly activated the rate of respiration greatly slows, but as it is still subject to the spatial dimension energies involving this center may both be shaped and accumulated.
When used in a pure manner it results in the body moving very slowly. The tai chi phenomena of “swimming through air” is display of this force. Likewise if you see a monk walking very slowly down a path they are usually practicing with this energy. Martially this can be used to throw an opponent. When this occurs, the sensation is that a very soft force unhooks your feet, or root, from the ground and you observe your body moving off to the side without the ability to do anything about it.
As astral energy may be accumulated it can also be circulated through the macro/microcosmic circulation exercises as well. This tends to clear the body of emotional static and allows for martial development as well. While time consuming, frequent work with astral energy allows a practitioner to, in effect, use the astral force with greater speed. Although this may be a matter of simply being able to access the astral force with greater ability.
The astral center is also related to the elemental energies as they are timeless while still having a spatial component. The astral energies do not store themselves in astral center, but share many characteristics with astral force. Most systems have a banding process where the elemental energies are manipulated, and potentially stored, in specific sections of the body. The elemental energies all have a relationship with the emotions and sense gates (i.e. vision, hearing, touch, taste and smell) of the body as well and a responsible for a variety of the passive esoteric abilities (i.e. clairvoyance, clairaudience and clairsentience).
The mental center in the body is not subject to either the sensation of time or space and the energies of this center, and above, cannot be accumulated.
The three primary energies worked with at this level, and above, are pure mental energy, Akasha/ether and non-dual light. As timeless and spaceless energies a practitioner primarily works to improve their access to and control of these forces, but cannot effectively shape them.
Mental energy in its pure form can be used martially and is often displayed in “empty force” demonstrations. The effective application of this towards moving another physical body is primarily limited by a variety of skills need to access the energetic/fasciae networks of another human being and as such is difficult at best to use and typically falls into the category of a parlor trick. When being thrown by this most people will describe feeling no sensation of any kind and merely state that they were looking at their opponent and that their body suddenly moved.
In meditation, or theurgic practice, the mental center acts as a kind of gateway to states of consciousness that exist beyond state and time. Mental energy itself is used in expansion and under no circumstances should any effort be made to condense or shape this force.
Akasha/ether manifests as a kind of deep purple force that is both spaceless and timeless. It is related to the throat energy center and effectively represents the power of the void between the astral center and pure consciousness as represented by the mental center and beyond. When viewing tantric icons of saints it is represented by a thin purple layer surrounding the saints body.
As a practical matter the elements can be pulled out of Akashic force in a much purer and stronger manner than they can be pulled from the natural environment surrounding a practitioner. Additionally, Akashic force is extremely draining on a practitioner to use and somewhat narcotic. Its primary theurgic effect is to remove desire and extensive use of this can leave you sitting on a couch for weeks a time with no memory of what the hell happened.
Non-dual light is the light of pure consciousness. Most cultures associate this with awareness, or merging, with God. As being beyond the sensations of space and time it cannot be shaped or controlled. A practitioner can only work to improve their access to this force.