xingyijuan wrote: How can the "energy'" transfer to the target if the fist is not tight? When you punch, you try to have your fist as tight as possible at the last possible moment, am I right?
Totally disagree.
As long as you can maintain structural integrity of your fist, energy will transfer from your arm into the body. Simple physics.
You can even punch with your four fingers completely hanging loose, but keeping your knuckles in line with your wrist, forearm and elbow. I've been told when I strike like that it's heavy enough.