Do you use chi? Or even give it any valid thought concerning your martial arts practice? If not, or if so, why?

I study chinese medicine so I'll give my take on the subject. Qi is not tangible like electricity or heat or atomic. One could even argue that using the word "energy" to describe it is wrong. It is definitely wrong.

When the Chinese spoke about qi they spoke about it as a verb (in action)and not a noun(as energy). The clouds moving is qi. When you get angry and start exhaling loudly or sighing that is your qi rising. When you get depressed your qi is slow. When you get too happy and start weeping for no reason your qi is disordered. When two fighters are fighting you can tell if their yang qi has risen or not. Chael Sonnen looks kind of nervous and always looks down right before the fight begins but as soon as the fight begins he goes full ape. That is an example of his yang qi rising. Anderson Silva on the other hand starts kind of slow(because he sucks and is mainly a counterstriker, lol). He measures distance for a round and then finally opens up later in the first round or the second round. His qi is slightly sunken at the moment the fight starts. If I'm being tortured I think I'd be able to stand more punishment if I"m in ape •••• mode as opposed to depressed or nervous which would cause me to give in earlier.

Can qi be used in a fight? Sure. When your yang qi has risen you are more aware, paying attention to everything the other person is doing, your adrenaline is rushing which causes you to feel less pain.

Qi can be used another way in fighting as well. When you get knocked out your qi(and oxygen) gets stopped at the moment you get hit closing off it's flow. So I guess in this instance you are using the other person's qi against him.

This probably wasnt the answer you were looking for, Robert, but it's all I got. I find focusing on my breath while wrestling helps me maintain mental equalibrium and helps me keep my wind better. Do I lose my mental power when my stamina is low? Definitely. Would I lose steam faster if I wasn't focused? Maybe. Who knows. The Shadow knows.