|A front fore fist punch with the |
reverse arm pulled back towards
the hip. (Image Source)
A lot of Taekwon-Do training occurs without hitting an actual target and many of the punches and kicks are done in the air, without any contact. During such training the reaction arm is crucial for keeping good balance and structural alignment. Not doing so may lead to bad habits and overextension of joints, which could lead to long term ailments. However, when you actually do hit something, the reaction arm is not necessarily required because the object you are hitting is providing the reaction force as we know, based on Newton's Third Law of Motion. In other words, when you train against a punching bag or when you actually hit a person, you may at times, and sometimes should, opt to do it without the reaction arm. In ITF Taekwon-Do we actually see this. Certain training is done with the reaction arm (e.g. fundamental technique training), while other exercises are done without the reaction arm (e.g. tournament sparring drills). The discrepancy doesn't mean that the one is “traditional” and the other “practical,” it merely means that one form of training assumes more force that could affect your structure and another form of training that assumes that you will be hitting actual objects.
|A knife-hand inward strike with |
the reverse arm covering the torso.
|Me demonstrating an arm|
bar: pulling with one hand,
while pressing with the other.
These are the two main ideas regarding the reaction arm in ITF Taekwon-Do. The first is that it acts as a reaction force that helps with proper balance and postural structure, which is especially necessary when practicing without the presence of a physical target. If you do hit an actual target you may often omit the reaction arm because the object will provide the reaction force according to Newton's Third Law of Motion. The second interpretation of the reaction arm is that it functions as a pull, which combines with the forward momentum of your attack, resulting in a more forceful collision. The reaction arm may also be part of other pull-push combination techniques.
What are your thoughts on the reaction arm?
Read my follow-up post on the reaction arm, which presents a third view based on centrifugal force: "Another Perspective on the Reaction Arm."