Bruce Lee once said that the difference
between a Karate punch and a Gongfu punch was that a Karate punch
is like being hit with a crowbar, while a Gongfu punch is like
being hit by a metal ball on the end of a chain.
This
describes how the right amount of relaxation can speed up a punch
and make its impact more explosive. The striking arm can also
recoil back to a guard position more quickly and is therefore
less likely to be grabbed by the defender.
Another
consideration as that for a Karate punch the whole body is rigid,
which has the effect of making the Karateka fairly easy to topple,
rather like a statue. The Gongfu practitioner should have a softer,
more adaptable and rooted posture, more like a Willow tree than
a mighty Oak. A final point is that by eliminating any unnecessary
use of muscular force, the Gongfu fighter also expends less energy
thus minimising fatigue.
So
how does a Taijiquan fighter access and release this explosive
power? If we are to believe practitioners of most of the descendant
styles of Taiji (Yang style and its derivatives), we should not
release power during practise. From my own training and teaching
experience, I firmly believe this to be nonsense. Training at
full combat speed and training your body how to brace against
impact is essential training for any martial artist.
"Emphasis
on slow movements alone leads to slow strikes which an opponent
can counter easily. Emphasis
on fast moves only makes it difficult to feel the path of your
energy and makes it easy to strike along a longer path than necessary.
Being fast refers to the speed generated through familiarity of
the energy path. It is a speed without loss of quality" - From
"Training for Sparring" by Chen Zhaokui
"I
am a firm believer in heavy bag and percussion training. I do
not like my fighters to train on a bag that weighs less than 80
pounds. The bag should have a firmness consistent with that of
softened rock. In other words, whatever the filling, the bag must
be quite dense. A fighter must condition his hands, feet, elbows
and knees to the shock of impact. Otherwise, all other preparations
for combat become useless. When properly conditioned, a fighter
has no apprehension about unloading a full-power strike on the
opponent. Poor conditioning leads to a fear of injury." - From
"Kuoshu Winning Secrets; Power Training" by
Mike Patterson
"No
one ever became a champion Olympic sprinter just by practising
walking" - Bruce Lee
The
following illustrations will attempt to show levels of relative
muscular tension during a fa jin strike.

The
white portions of the body show only peng or background tension.
The power (jin) surges up from the rear heel through each muscle
in turn, adding acceleration through each successive joint. The
red areas show the body parts where the momentum is currently
being accelerated and the orange through to yellow sections show
the slight increase of peng strength necessary to brace against
the impact. The fighter should not rise up as her power pushes
through her body, rather she should sink lower and compress to
brace. The whole process should happen in a fraction of a second.
Notice how the whole body returns to its"background" peng levels
once the power has been released so that she may return to a state
whereby she is equally ready to move any portion of her body.