Chi Kung Produce Energy with Oxygen
When we breathe the air into the lungs, the oxygen is carried out of the lungs by the blood; and also return the carbon dioxide to the lungs to exhale. The blood also carry the oxygen into the body cells. Inside the body cell, the energy is generated by the mitochondria.

Here is the chemical formula to show how the energy was generated:
Glucose + Oxygen = Carbon dioxide + Water + Heat + Energy(ATP)

On the left hand side, the glucose is from the foods we ate; and the oxygen is from breathing. Without oxygen we cannot generate the four things at the right hand side of the formula. The formula is telling us that more oxygen we inhale the more energy we will generate. With the muscle slightly contacted more heat and energy will be generated. Oxygen by itself is not an energy. It aids the body cells to generate energy. Oxygen do not flow inside our body but circulated by the blood pumped by the heart.

There is no universal energy we can breathe into our body. It is only a myth. Just remember when you breathe, you filled your lungs with oxygen. The longer you can hold it, the more time you allowed for the blood to carry more oxygen to your body cells. The more oxygen in the body cells, the more energy will be generated. Your excess of body heat will make you sweat which is the water you see in the formula. The poison gas you exhale is the carbon dioxide.

The body cell without oxygen cannot produce energy to carry its function eventually dies. The excess of energy generated by the cells is our body strength. We use the body strength to lift weights. That is why we always take a deep breath before lifting any heavy objects. The ancient Chinese people knew about this concept but don't know why. Without any scientific knowledge at the time, they thought it was some universal energy in the air that we breath and flow in our body.
The ancient people knew that the more air they breathe will make them stronger and healthier, but do they know what is taking place inside the body cell at the time? Do they know how the energy was generated? Are we still going to stay with the concept that energy is flowing into our body from thin air?

So, Chi Kung is only a breathing method to provide a maximum volume of air intake to the lungs. Do you know without the heart pumping blood into the lungs, the oxygen is going nowhere? Do you know that the heart muscle cells use the oxygen first, from the lungs, to generate the energy for the muscle contraction so blood can be circulated throughout the body. Again without oxygen, the heart dies. Now do we see why that oxygen is so important to us. Wow, let's practice Chi Kung.