Dragon Energy

The Dragon Force (竜勢力,Ryūseiryoku) is an unnamed ancient energy which predates both the Shinju and even the appearance of animal sages. It is energy which traverses through the earth, wind, sunlight and water. With each element playing a pivotal role in the survival of living creatures, Dragon Force is often cited as the energy that nourishes life. Food. Drink. Sunlight. It is an unseen energy that traverses life. An infinite source of power which flows through the Dragon Veins (龍脈, Ryūmyaku). A network similar to that found within humans. The earth's Dragon Veins are expressways located throughout the world. Connecting the highest mountains to the lowest rivers and everything between. All living creatures consume the dragon force. It is what supplies them with energy for natural bodily functions. It's the nourishment which physical energy draws from cells. Dragon Force is continuously consumed through life-sustaining activities. As it is the source of all living creatures. Dragon Force is the energy intertwined in every breath taken. In foods and drink consumed. As well as the ambient flow which courses through one's body while they sleep. It allows living creatures to continue onwards in life.

When utilized, the Dragon Force exits the body through various methods, transforming it into a new state. Natural Energy. It is often compared to humans inhaling oxygen and exhaling carbon dioxide. It follows an ancient principle. That energy can neither be created nor destroyed but only converted. Once a living body utilizes the energy within cells through physical activities or even ninjutsu, the energy is converted to natural energy. Which is reabsorbed into plants, turned into dragon force, and introduced back into the cycle.

It is speculated that the, who was spawned from the blood of thousands, was created due to the energy being converted to Natural Energy upon their death. Before amalgamating into one gigantic deity composed of Senjutsu chakra. Essentially making It's just what occurs when this energy is consumed; The production of physical and spiritual energy.

The Difference Between Dragon Force, Natural Energy and Physical Energy
A major difference is it's source. As shown by Kabuto's infamous technique, natural energy is not found in the earth's natural elements. And since people don't gather natural energy from consuming animals, plant life, and drinking water, one can speculate that it isn't found from actual components of nature. Instead, natural energy finds it's source from living creatures. In a way, animals take in this unnamed force from eating, drinking and breathing and convert it into natural energy. Senjutsu involves using this natural energy and balancing it with simple chakra. This can explain why most sages have animal traits and masters. Hashirama being the exception, learned how to draw natural energy from living creatures in general. Also, those who possess Jugo's bloodline limit continuously absorb the exhaled natural energy created by living creatures. Since living creatures are constantly creating natural energy, it is an abundant source of power. Which explains their continuous rages. Physical Energy, or Yang Energy, draws upon the energy within the cells of living creatures. Essentially making Dragon Force the source for physical energy.

Trivia

 * A theory created by Chart and I.
 * Inspired by Qi and the Feng Shui