Originally Posted by Cut Me Mick
Just read a few articles on the subject. My understanding from what i read is the biceps and triceps help deliver the power, they're not the agonists during a punch.
More specifically, the triceps are for speed of straight punches. The biceps are for the speed and snap of your hooks and uppercuts. keep arms lean and fast so you can get those fast punches and fast combinations in. The lower body adds power and the arms add speed.
I don't know what you read but it sounds like the information from an internet blog boxing 'expert'. What you're saying doesn't make any sense anatomically or biomechanically. The whole body adds power and speed through the kinetic chain, having lean arms or not makes no difference to anything, they are light relatively speaking and the difference in weight between a slightly bulkier arm and a lean arm would be insignificant. It's the last link of the chain so you don't have to put in any effort to overcome the weight of your arm if you're punching anywhere near correctly.