I personally think Qi and Qigong are far to overmystified.
This is done mostly by the crystal ball reading set or the hippies in west LA if ya get my inference.
In the simplest terms, Qi is that energy which animates you. YOur life essence. It is the energies that flow through you, it punmps your blood, it fills you with oxygen, it sparks ideas in your mind etc etc.
Qigong, is working with the mechanics of your own life essence and focusing on individual aspects of it. Much like isolation training in weight lifting for instance.
Some qigongs focus on making the breath longer and stronger and so endurance is enhanced.
In weight lifting, you can focus on your muscles in the arms.
In Qigong, you can focus on the optimal blood flow and oxygen getting to those arms.
A very simple form of Qigong(breathwork) is when fighting to breath out when you strike and to breath in when you retract.
Now this isn't called qigong in other cultures, but in essence it IS breathwork.
Getting rid a stale energis in the body can also be done using these methods.
Healing qigong has similarities to teh practice of Reiki or the Slavic and Russian fields of psychoenergetic healing or the east indian methods of yogic breathing.
every cultura has a version, THe Indians have Prana, the Chinese their Qigong and in North America we have wind sprints LOL.
Anyway, I think the Indians and teh Chinese Have really elevated it to a highly refined artform, I personally think there are many gongs that have value to health works and toe martial arts inasamuch as they enhance the main goals and objectives.
I also think there are far too many flakes putting far too many flaky spins on what is actually a really great method of exercises by wrapping it up in a bunch of mystical hoodoo.
To the babes goes milk and to the strong goes meat. If you don't have teeth, don't even try to bite into the meat. And if you've been eating meat for a while, you should know better than to feed it to babes.
toodles