Power is generated in a combination of ways;
Reaction Force: This is using another part of the body as an opposite force, i.e. pulling the lead hand back when following a jab with a cross. We can generate a lot more force when pulling and the rotation of the hips and/or shoulders will help generate increased power in the follow up technique.
Bodyweight: The subtle act of dropping or shifting the bodyweight just prior to impact helps to transfer some of that bodyweight to the striking tool.
Hip and shoulder twist: Every punch should use hip twist using a whiplash effect to use the body’s momentum to transfer energy to the striking tool. To maximize power, the hip twist occurs a split second before the punch is thrown. When combined with the shift in bodyweight and shoulder rotation, this allows you to strike with much more force.
Focus: This is harder to grasp. Basically this is the act of concentrating on the technique that you are performing. With proper focus you can “channel” all your efforts into the technique and produce more power. Focus is greatly aided by proper breathing.
Breathing, tension and relaxation: When performing a technique, you should breathe out sharply so that the air is expelled just prior to impact. A short, explosive exhalation of breath tenses then relaxes the abdominal muscles, which increases power to the major muscle groups and prevents impacts from “winding” you. When you strike you should think about healing the person you are striking, this is a strange concept but aligns with the idea of tension and relaxation. When you strike and your body is tense some of the power is not directed into your opponent but back at you, in effect your strike does not penetrate into the body. If you look at massage techniques you will see the hand is relaxed when striking the body and when the masseur hits the body the strike goes deep into the muscle. When we relax the strike will penetrate deeper into the body and stay in the body.
With enough practice, the student can learn to instinctively combine all the above elements. True power is fluid and almost effortless. Tensing up and trying to hit hard creates the opposite effect, as your muscles work against each other and make your techniques less powerful. Relaxing between each burst of power is more productive. Power is not about physical size, but about the application of the correct technique.