I'm always intrigued with Eastern traditions like Shaolin that integrate their physical and martial arts practices with their religion. It makes me a little envious since I'm not aware of a similar tradition within Christianity. If there is I'd really be interested in hearing about it.
In Medieval times people participated in bodily mortifications, but they were more intended to damage the body in order to bring it's passions under control. What I'm working on now is a way of developing a healthy body in a way that consistent with the Gospel message.
The biggest impact recently on this endevor came when I read N.T. Wright's "Surprised By Hope." Wright, a Bishop in the Church of England, challenges us to rethink the point of Christianity. He maintains that it's not, "Going to Heaven when you die," but rather that at the second coming all people will be resurrected from the dead and receive new bodies. This hope is made clear at Easter, when we celebrate Jesus' resurrection from the dead and all that it entailed. Wright described the process as all of the matter consisting of his old body was used up in creating his new body. This new body was in many ways similar but also profoundly different. The disciples on the road to Emmaus didn't recognize him until he broke the bread. Mary Magdelene thought he was the gardner until he called her name. At the same time he wasn't completely different. He still had the scars in his hands and wrists and he invited Thomas to touch them. He even ate food in the presense of his disciples.
The resurrection also provided him with some new abilities. For one he could enter into locked rooms without disturbing the door or windows. And at the end of Luke's gospel, his body "ascends" into heaven - though not in the sense of him raising up in the air. Instead Jesus, bodily, passes between this world and the world where God abides. To this day we wait until the time when those two worlds are joined like a husband and wife.
All of this leads us to believe that the point isn't to enter heaven as some disembodied ghost, but to enter it bodily - with our new bodies given at the final resurrection and exist with God as full, breathing, living human beings. When people misunderstand this they slip into a type of dualism where matter is considered bad and spirit is considered good. (I'm grossly overstating this but you get the point.)
So what does this have to do with flow, physical disciplines, and martial arts? Through baptism, Christians are said to be united to Christ in both his death and resurrection. Mystically we have died and are given our new bodies in resurrection. Therefore the whole point of the Christian life is to live, as much as possible, in this world as if we're living in the next world. We always pray, thy kingdom come, thy will be done on earth as it is in Heaven. Whereas once our bodies were corruptible, now they are incorruptible. Whereas before we engaged in sexual immorality, envy, murder, strife, craftiness, gossip, greed, etc. we can now live in ways that are generous, loving, and hospitable. It's not the difference between spirit and matter that makes this possible, but the difference between the old body and the new body.
So why train in CST? I find that when I'm in my flow, it's so much easier to be generous, loving, kind, and hospitable. I have so much more energy to do the good works God has set out for me to do. In short, a body that's in flow looks so much more like the resurrected body than it does to the old body, the one damaged and tramautized by sin, death, and corruption. CST, and unbinding my flow has become a way of reclaiming the body that God has always intended.