The bigger guy will not always win. Even though, 1 true fact about a bigger fighter is that, the bigger the puncher, the greater the whiplash and mass in a punch you will impact on the opponent. Speed and power are vital. Remember, speed wont do [censored] without power behind it. Power will knock the guy down, or out, speed could possibly be useless.

Now when you punch, various muscles are used to do different things. Some people think that the guy with the huge chest, the huge biceps or huge shoulders will always win. And believe me, from personal experience, its simply not true.

Now heres a list of muscles in no particular order that are involved in a punch, and basically what they do. And im not [censored] you, i know what im talking about

BICEPS-

Believe me, they have a serious job, in a punch..The Biceps most definitely are involved in " An Uppercut " " Hook " and the " HayMaker". In an uppercut, a stronger bicep gives you the advantaged to hook your arm with power during an uppercut, and stabalizes the punch. In a hook, it will stabalize the punch and give you extra power as you strike. And same for a haymaker.

Even during a straight and normal punch, the bicep prevents you from over extending your arm and causing damage to your elbow and vital ligaments. Also, ever notice that when youre in a stance and have your hands up, your bicep is pumped? With that, when you throw a punch, your bicep contracts and adds blow to the punch. It also will allow you to bring your hands back quicker which in turn means, youl strike again faster.

Triceps-

Basically a tricep releases power when it is extended in a punch, a strong tricep gives the push and strike power in a punch. And in boxing, the stronger the tricep, the easier it is for you to block a punch with your hands as you strike and knock away your opponents hands.

Shoulders, Chest, Back Muscles-

These 3 muscles are vital ina punch. The shoulder gives rotation for a punch as the back twists and contracts and the chest muscles add extreme power to a punch. The chest muscles are mainly involved in hooks and striaght punches. The shoulders play a important role in all punches..Back muscles add blow to the punch.

Hip Flexors, Legs, Abdominal Muscles-

As we know, power is generated from the ground up, in a punch. Strong legs are very important, if not the most important during a punch. The stronger the legs, the greater whiplash and engery and power you generate which travels up the body through the large muscles in your back and strong hips will allow a great amount of power to be released as you twist your body and swing into a punch.

Forearms-

The stronger the forearm, the tighter your fist. The tighter the fist, the more impact you release in a punch and the greater chance of injuring any other muscle in a punch, just in case you mispunch, the more of that backfiring impact your forearm will absorb. Forearms also add power to the punch upon impact.

* NECK *

Believe it or not, the stronger your neck, the greater your chance of takign a serious blow, and not getting knocked out is. The stronger the neck, the more impact from a punch you can take. ( Boxing, Martial Arts trick )
Hope i helped, because hitting harder seems to have been a issue for quite some time.

legs, hips core and shoulders.

Arms do very little. If you get a major 'pump' in your bi's when punching, your mechanics are waaay out.
Think of the legs and torso as the handle of the bullwhip, and the arms as the tip. The power comes from the handle and is transferred through to the tip. trying to add significant force via the bi's and tri's merely acts as impedance to the main power source. arms should remain relatively relaxed or you end up 'arm punching' which is useless.
The closer the range of the punch, the less arm involvement there is, so hooks and uppercuts use less, not more arm engagement.
I appreciate your enthusiasm, but your 'facts' are sadly incorrect.

Good guide. How about the wrist?

Agreed with Cord. Arms in general have comparitively little involvement as far as power generation of strikes. Good hooks and uppercuts rely mostly on body mechanics, not arm action.

Not to say that strengthening won't help - I am a big fan. But I think it's important not to overstate the effects of given muscle groups.