The term “energy” has several meanings often conflicting. In terms of Kempo, we should consider the scientific notion defined as:
“In physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law. Different forms of energy include kinetic, potential, thermal, gravitational, sound, light, elastic, and electromagnetic energy. The forms of energy are often named after a related force.” (wikipedia.org, 7/31/09)
This can be shorted to “Energy is a physical quantity that describes the amount of work that can be performed by a force.” In Kempo, we use kinetic energy since that is the physical interaction that we use.
“The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity.” (wikipedia.org, 7/31/09)
Therefore, the more motion you generate on an object the more energy it has. This is why we use constant striking, letting one attack continue on its trajectory into another attack. We try not to start and stop a fist. Rather, we punch and let it flow into another punch. This maintains the energy of the strike without dissipating it.
Martial arts tend to have it fair share of spiritual terms that cross-pollinate its concepts. One is Chi or Mana defined as:
“In many cases “energy” is conceived of as a universal life force: to this extent ‘spiritual energy’ theories resemble vitalism and may even invoke the Luminiferous Ether of Victorian physics. Additionally, or alternatively, such notions are often aligned with or derived from conceptions found in other cultures, such as the Chinese idea of Qi and the Prana of the Upanishads.” (wikipedia.org, 7/31/09)
What we see here is several cultures have this concept of breath or life force. It is this force that Chi Gung and Dim Mak practitioners utilize for their secret, deadly techniques. Whether or not this hokum is true, the common trait of this force is its ability to flow.
This is the key to using “energy” as a visual tool. You imagine that it flows through the body. What do you imagine flowing? Their center of balance and momentum is the sloshing “fluid”. By seeing this as a thing (like water in a bathtub), you can imagine how to manipulate it. Push it. Pull it. Then it develops a momentum that can overtake the opponent. Their own balance becomes their weakness.
The opponent’s body reacts to strikes in a certain manner along biomechanical constraints. It is the flow of combat and it is easier to imagine it as fluid than a series of interconnected bones and muscle groups. Admittedly, this is a mental crutch but it can pay off in technique application when you’re in the heat of battle. It is easier for the brain to process this sort of calculations than thinking of the actual physics involved.
Wikipedia (English) under the topics Energy, Kinetic_energy and Energy_(esotericism).