Reaction Force

Any upper body basic movement in Taekwondo should use reaction force. Reaction force is the method of using both sides of your body instead of one thus maximizing your power.

E.g. If you are executing a one-handed block or strike you can at least double your power by pulling your spare hand tightly back onto your hip at the same speed as you throw your technique forward. By using both sides of your body you generate more power than by just using a single arm.

Every single movement you practice in taekwondo should, if being carried out technically correct, use both arms, with one arm being the reaction force arm and coming back to your hip at speed and the other executing the technique.