Shambala publishes a book called Sword of No Sword by John Stevens that should be of interest to all teachers. That does not mean I agree with everything in it, but it stresses the strength of spirituality in the type of art we’re interested in.
Experts in martial arts disciplines in Japan and China learned how to project Ki (Chi). In Sword of No Sword, the warrior Tesshu (who never killed a man) asks a famous swordsman how he remained undefeated. The answer was, “As soon as the challenge was made, I maneuvered close enough to feel the tip of my opponent’s blade. If he was holding the sword stiffly, I knew I had him – one swoop and he would be finished. If, on the other hand, the sword was held flexibly with a steady projection of Ki, I took no chances – I threw my sword at him and ran. That’s how I remained undefeated.”
The Kahunas of Hawaii would charge spears with Vital Force before they hurled them in battle.
This should ring true to T’ai Chi Chih teachers; we watch the wrists and the waist to see if there is tension (and the Chi can’t flow) or softness and relaxation.