these boxers who "pump" up they're muscles i agree have got it wrong because they naively follow a typical bodybuilder style weight lifting plan
A punch starts in the toes and ends in the fist. Every muscle in between plays a role. You can have terrific legs but if your core can't transfer that power it's 100% worthless. In other words you don't need strong legs you need a strong body. Focusing on a muscle group is totally useless IMO.
you are correct that not everyone can be huge punchers but whats wrong with increasing power to an extent? what you don't probably know is strength can be acquired WITHOUT ADDING WEIGHT with or without iron i do heavy squats for my legs and the result is i have far more spring, quicker on my feet and hit harder what can be wrong with that? also did you know weight training increases tendon strength and bone density and protects against injuries? (you said it yourself but why limit it to fingers and hands?)
yes absolutely the obliques and abs, back must be strengthened too cable twist is good for the twisting motion
i use medicine ball throws (it will also help with ur balance and control). 8-12 lbs just like a punch but ur pushing the ball in the motion of a punch against the wall bout 10-12 feet away. thats just 1 i do. But it its true alot of it comes from ur legs and hip rotation
i have an idea for you attach a shot put ball (smaller than the standard though) to a rope and suspend the rope from a beam it fits in your hand easily and you don't have to tense your shoulders holding it up before throwing it add to this a weighted vest for resistance on the torso and legs
I have an idea that is less trouble setting up. Attach a 16 ounce weight to each hand, and then throw those weights at a not too hard surface, like a leather bag filled with cloth for example. :think
After finding the source, I realized I had initially read it in a book I have called Power by the Squat Doctor himself. Here is a piece and the link to the full page:thumbsup I was also wrong about the percentage(70) There have been some very interesting soviet studies on what makes a technically sound punch. The soviets looked at 120 boxers ranging from amateurs to experienced professionals. This study found that among the highest level boxers, the highest percent of their power (38.46%) came from the push-off of their back leg, whereas the arm extension and trunk rotation accounted for 24.12% and 37.42% respectively. Even more interesting was that the high level boxers were more ‘well rounded' with their power development compared to the less experienced boxers (arm extension 37.99%, trunk rotation 45.50% and leg extension 16.51%). This shows that with an increase in boxing skill and experience, boxers improve coordination between arm, leg and trunk movements. http://drsquat.com/content/punching-power
another idea i have is to put on wrist weights(must be very light though) ankle weights and a weighted vest and throw punches in the water not sure if the weights will help a great deal in stopping the floeting effect which interferes with the whole body technique as i don't know of anyone who has ever tried it also you can do a much higher volume of punches without having to retrieve an implement probably a good idea to wear footwear too lucky i have a pool in the garden