while the majority of my training has been in karate, it is my belief that these principles are for the most part universal, as they deal with body mechanics in general as opposed to specific practices or techniques
Tense muscles are
strong, but they are also
slow and difficult to move. This is a good thing for a finished
technique, as it makes it less likely for your strike to bounce off its target, and makes it harder for an
opponents
block to move.
Loose muscles are
fast, and move freely, but they do not have a lot of
strength. This works well during the
execution of a technique, when the most important thing is getting from the start of it to the end as quickly and
efficiently as possible.
An
effective technique is one that uses the both types of
muscle tension, taking
advantage of their
strengths, and avoiding their
weaknesses. A good
punch, for example is like a
whip, flowing out loosely, and then snapping tight at the end.
In
combinations of more than one technique, this
transition between loose and tense gains a new
layer to be practiced. When your muscles are already tense (i.e. at the end of a technique), they must be relaxed for the next technique. Simply relaxing the muscles works, but it takes an extra fraction of a second, and all of the energy stored in the muscles is dissapated. Releasing the tension as you begin the technique
directs the energy into the movement, and makes it slightly faster.
Proper muscle tension is
critical to efficient technique. Tense up too often, and you end up pushing more than striking as you work against your own body. Stay too loose and your techniques, while quick, are unlikely to
penetrate. It is this fine line between bashing and slapping your opponent with a wet noodle you must walk.