First of all, let me point out that muscles do not “expand” so much as they “lengthen” and “contract” is slightly misleading as well. What is often meant by contraction/expansion in Karate, however, is not so much an explanation of what the muscles do, as a relational description of the movements of various parts of the body. These parts (usually 2 joints) move closer to and further from each other due to the amount of flexion in a joint between them. This is the type of contraction/expansion that I would like to discuss here.
This type of flexing movement usually involves a tensing of certain muscles during the “contraction” portion of the movement. But, contrary to what many may like you to believe, the difference in overall muscle tension is often not much different in a “contraction” move than an “expansion” move. This is due to the fact that while muscles on one side (of the arm, for example) are tensing/shortening, the muscles on the other side usually relax/lengthen to compensate. It is true that one can tense a majority of muscles at once, or relax almost all the muscles at once. Although there is often a noticeable difference between the total amount of muscle tension in your body at impact/completion of a technique and the relatively relaxed state of preparation, the overall tension should not differ much during the pre-impact portion of execution of quick karate techniques.
So why all the emphasis on contraction/expansion? If you are trying to think of “squeezing” and “stretching” muscles, maybe you should concentrate on the individual muscles involved. Sometimes, it is advantageous to break down a move into the component parts to analyze the various tensions involved. But I think a more obvious way to think about this is to simply study the movement of the joints. The muscles will do their work if the various body parts are moving in the proper ways. And it’s easier to keep track of, for example, where your knee is, than how much your various leg muscles are shortening/lengthening during a movement.
If you refer to my February article, “Tension vs Relaxation”, you can see that I have already discussed a related point. As I mentioned in that article, it is usually advantageous to relax muscles to increase speed, and tighten muscles to gain more connection to the rest of the body, both of which help create force (Force = Mass x Acceleration–I will discuss this in more detail in a future article). So if we are trying to maximize speed in a technique (in this example, a punch), why would we want to “contract” (=tense) our muscles? This is my point. There can be a contraction between different body parts (closing the distance between the two points) existing with minimal muscle tension. In the case of a punch, there is a certain amount of muscle tension required to launch the fist towards the target. But the muscles which should be tensed are those of the torso more than that of the arms (There is always some tension in the legs, but that’s a different story-again, see the February article for further comments). So while the punching arm is bent during the starting phase of the technique, the muscles of the arm are more relaxed. And when the arm is extended, the muscles momentarily tense. So the “contraction/expansion” of muscles is sometimes the opposite of the “contraction/expansion” of the moving body parts.
Copyright © 2022, Jon Keeling (originally published May 1998)