If you want to work on the speed element of any kind of striking (including punching), there are some exercises that I've found which I believe will be helpful. I know I've mentioned some of these in other contexts, but I will repeat them here so you have them all in one place:
- Slow-Motion Practice -- Have you ever seen anyone practice Tai Chi? All the movements are slow, relaxed and graceful. When practiced as a martial art, the slow, easy movements of Tai Chi result in very quick and powerful strikes. I believe the rationale behind this is that performing the movements in a slow and relaxed manner allows the brain to distinguish the muscles necessary to the moves from those that are not. I was shocked at the power I developed in my brush, check, strike when I used this method
- External Resistance Practice -- I know that some of the karate-based arts practice kicking and striking in water up to the neck. The water provides resistance, and you feel which muscles are pushing against the water. Although the water slows down the moves, you try to execute your strikes as quickly as possible against the resistance.
- Self-Resistance Practice -- This may seem counter-intuitive, but it seems to work. It's a variation of Slow-Motion Practice, but you tense your muscles as you perform. If you're familiar with the sanchin kata of Shito Ryu karate, you will understand what I'm talking about. In this kind of practice, you deliberately tense your opposing muscle groups so that they work against each other. The movements are slow, deliberate, and difficult to execute. If you do it properly, your striking limb should quiver from the tension. This kind of movement provides an excellent workout, and will strengthen the muscle groups involved more effectively and more safely than working out with weights. I think it helps speed because it creates more body-and-muscle awareness.
- Mental Visualization Practice -- When I was in grade school, my friends and I would make elementary animated drawings on our writing tablets using stick figures. In drawing # 1, the figure would be in a normal, standing position; in drawing #2, his legs and arms would be out to the sides. By flipping the page back and forth, we could make it look as though the figure was leaping/dancing. In Mental Visualization Pracice, you see in your mind the beginning and ending positions of the strike you are working on. You have to see it from your own, subjective perspective. For example, you see in your mind's eye an orc standing in front of you, with your hands in the ready position. Then you see your hand at the completion of a palm heel strike. When you have these images firmly in mind, you "flip" back and forth between them. No in-betweens at all. Your brain will send low level impulses along the motor nerve pathways involved in the movement. On some level, your mind will also try to cause your actual strikes to imitate the incredible speed of your mental practice. This is how I developed a jab that amazed my jujitsu instructor who had boxed for eight years.