Babies breathe naturally using their diaphragms. As they age, at some point they start breathing unnaturally using their chest muscles. After years of breathing in this inefficient manner, it is difficult to train students to breathe properly. When learning to punch and kick properly, Taekwondo students experience the same problem; they have done punched and kicked incorrectly for so long it is difficult for them to learn the natural, proper way.
When students first learn to punch, they use their arm muscles and lean or reach with their shoulders; therefore, their power comes from whatever energy they are able to generate with their arm and shoulder muscles, and the mass of their arm. To generate maximum power in a punch or kick, one should sequentially apply power to the technique using all the muscle from the soles of the base foot or feet to the point of impact, and, at moment of impact, apply as much mass as possible to the point of impact. Learning to apply muscle power sequentially is usually not much of a problem for students, but learning to apply mass, using hip snap, tends to take longer to master.
The audible snap of a technique comes from acceleration of the fabric of the uniform at the end of the sleeve or pant leg. No person can accelerate his or her arm or leg fast enough forward to achieve this snapping sound. To achieve a snapping sound, one must retract the technique as quickly as it was extended, just as when a person snaps a whip or a towel. The snap itself is useless; it only provides feedback to the user that the required quickness has been achieved. To make a snapping technique useful, mass must be applied behind the technique. When a snapping towel hits you on the chest, it stings; when a snapping punch hits you on the chest, it breaks ribs.