When beginners are first taught to punch, they are taught to twist the fists and to pull one fist backward as the other is pushed forward. This motion is used to familiarize students with using equal and opposition reaction forces when using techniques. A question may be "Do the arms pull and push equally, or does one start or finish before the other?" This question is similar to a koan, a short and pithy but illogical statement used in meditation among Zen Buddhists, intended to free the mind from its rational mode of thought. For example, we know the sound of two hands clapping, but what is the sound of one hand clapping?
Most of us learned that the arms must start moving at the same time, move equally, and finish together, but is this true? While it does make learning the motion easier for beginning students, is this equal motion the best movement for more advanced students?
This punching koan does have an answer. For maximum power, the pulling arm starts first but finishes last. The pulling arm starts moving backward first so the reaction it generates will push the other arm, which starts moving at a higher acceleration than the pulling arm. At the higher acceleration rate, the punching arm reaches the target before the pulling arm gets all the way back so that the reaction force is still pushing the punching arm when it reaches it focus point.
What is the sound of one hand clapping? Silence!