Trapping is effective....... You just need to be able to pull
It off and that requires sparring.
I've read just about everything that was written by Bruce Lee or attributed to him and I do not recall him saying at anytime that trapping was ineffective. Please cite your source.
Some trapping is effective but it is stuff you would learn way down the road after you become proficient with energy training and other "trapping" concepts. It is taught so you can learn to fight by feel not so much by sight and you can use and feel the other persons energy to be able to react accordingly. In close quarters you don't have time or luxury of seeing what is or is about to happen. It helps you fit in to the situation and with the other guys fighting style.
With so many highly trained teachers saying it's ineffective including Bruce Lee after fighting Wong Jack Man why is it still stressed so much in JKD?
