Force equals mass times acceleration, which means that speed is a key component in striking with power. If you want to strike hard, you must also be able to strike fast. Here are a few simple things you can do to help increase your punching speed:
Punch. It really doesn’t get any simpler than that. You get better at things by doing them repeatedly. The more you punch correctly, the better your punches will become. After all, perfect practice makes perfect.
Use weight training. A fast, strong punch requires strong deltoids. The military press, cleans, clean and press and medicine ball throws are good for building the delts.
Shadow box. While shadow boxing, make a conscious effort to focus on throwing crisp, speedy punches.
Use a speed bag. Spend at least three rounds per session on the speed bag. The speed bag is excellent for tiring out the muscles and building muscle endurance. This is really important as the fight goes on and your arms grow heavier as you get more tired.
Hit the heavy bag, fast. Instead of concentrating on hitting the bag as hard as possible, try to his it as fast as you possibly can while still retaining good form and decent power. Remember your footwork and move around the bag. Don’t just stand in one place.
Relax. The key to speed is relaxation. You can’t extend you limb as fast as possible if you are overly tense. Tense the muscles just before impact. The rest of the time you should be relaxed.