It doesn't take an expert kinesiologist or doctor of sports medicine to see that there's been a major change in the way boxers have trained since the mid-20th century. Once upon a time, a boxer was instructed to stick to his punching bag and avoid weight training and bodybuilding like the plague. The fear was that too much musculature could render a fighter "musclebound" and lacking the necessary speed and agility. This concern was an issue not only in boxing but all major sports. Today, bodybuilding practices have been incorporated into the regimens of athletes in just about all sports, very definitely including boxing.
To get a sense of the change and how long it's been going on, compare pictures of middleweight champion Jake LaMotta circa 1945-50 with stills from Martin Scorsese's classic film biography of LaMotta, 1980's "Raging Bull." By modern standards, the young real LaMotta looks decidedly non-muscular, if not exactly flabby. By the time Robert De Niro portrayed him three decades later, however, it was clear that audiences would not accept a champion boxer looking quite so ordinary. In the early portions of the film, De Niro appears substantially more muscular and defined than the real LaMotta ever did.
Today, we know that bodybuilding techniques are hugely important to building and maintaining the strength and agility a good boxer needs, whether fighting in the ring or just sparring or practicing with a punching bag. Evander Holyfield and Mike Tyson were obvious examples of boxers with a decidedly muscular build, a look that is still controversial among some fight fans. While you would never see Holyfield or Tyson competing in Mr. Olympia competitions, they clearly had the built-up look of men who knew their way around a free weight room.
We're happy to say that it's become conventional wisdom that boxers should incorporate bodybuilding techniques in an intelligent and strategic fashion to increase their strength and endurance. Even a lightweight needs strong muscles and there's no reason any boxer, or any other athlete, should be afraid of incorporating natural and intelligent bodybuilding techniques.