All in the mind

According to researchers from Imperial College London and UCL, as reported in MailOnline a week ago, Bruce Lee's inch punch was more related to his connections in his fine-tuning of neural connections in the cerebellum, allowing him to synchronize his arm and trunk movements very accurately.  The research attracted more attention probably because of its mentioning of Bruce and using Karate Black belts doing punches versus untrained subjects.  I'm sure it will get the same result using other athletes, like professional golfers versus untrained counterparts.

The real pragmatic issue is :How to train oneself into such fine-tuning of neural connections in the cerebellum?

The most dominate factor in achieving that is, I believe, genetics.  People are just born with better athletic prowess, better connected bone-muscle structure and better neural connections in the first place.  And coaches of national athletic teams select those high-potential kids from primary schools and try to train them to compete in the Olympics some day.  Whereas common folks, i.e. most of us, have to be contended with whatever their lowly level of potentials, if any at all!

The practice of Chinese internal martial arts aims at trying to level the playing field.  The internal martial arts came from Taoist practice.  In ancient China, Taoist masters were a bunch of guys who were not willing to bow to nature, what nature endowed them with.  In the spiritual level, immortality was the goal, and in the physical level, revamping one's bone-cum-muscle structure was the objective.  The latter is called "Changing bones like rebirth - 脫胎換骨".  It is still a common phrase/concept in modern Chinese language, though the concept can now also refer to many different things, including [successful] plastic surgery!

And how to do it lies the whole discipline of Neidan (Taoist meditation) and internal martial arts.

Changing bones like rebirth - 脫胎換骨