The Rocky movies are fiction, Dave. That tells you pretty much all you need to know. But let me add some details.
First, we need to clear up the difference between force and pressure. Force is what causes something to accelerate, e.g., a fighter’s head in the direction of a thrown punch. In the United States, force is normally measured in pounds. Pressure is force per unit of contact area, commonly expressed in pounds per square inch (psi). When researchers study punching ability, they usually focus on force rather than pressure, since the pressure varies as the contact area expands on impact.
With that in mind, let’s look at the research:
If a punch thrown by Rocky IV villain Ivan Drago is supposed to measure 2,150 psi and his glove’s impact area is something like 4 square inches, he’d be exerting a force of 8,600 pounds, or more than four tons. Based on the professional literature, no boxer in real life comes anywhere close to that. I did find a 2007 news account about WBO cruiserweight champion Enzo Maccarinelli, whose punches supposedly packed a wallop of around 3.85 tons. However, the researchers making this claim have yet to publish their findings in a scientific journal, and I’m not taking them seriously until they do.
Even without Drago in the ring, boxing is a punishing sport, especially where the head is involved. Damage comes from three things: 1. the impact itself, which may be manifested in, say, a broken jaw; 2. acceleration to the brain leading to abrupt contact with the skull, possibly resulting in concussion; and 3. the rotational force that twists the brain within the skull, increasing the severity of injury and the likelihood of a knockout.
One metric for gauging the risk and seriousness of a brain injury is the Wayne State tolerance curve, which looks at both the g-force imparted to the head and the span of time involved. Generally speaking, you don’t want to take a shot of more than 50 g, although you can stand more if the impact is really brief—say, a couple thousandths of a second. If you’re on the receiving end of a Bruno-class impact, my guess is you won’t soon get up.
Punches to the head can cause detached retinas, brain hemorrhage, fractured bones and permanent neurological disorders. As I’ve mentioned before, something like a fifth of boxers suffer from dementia pugilistica, the consequence of repeated blows to the skull; it’s characterized by slurred speech and halting gait. Worse can happen. According to one estimate, boxing killed at least 650 fighters from 1918 through 1997.
Mixed martial arts (MMA) fighters, interestingly, seem to be less at risk. Since MMA rules allow grappling (meaning less punching) and tapouts (giving up), actual knockouts occur only half as often as in boxing.
Besides maybe getting killed, cumulative brain damage is the scariest part of boxing, as most fighters now recognize. To quote Terry Marsh, the undefeated light welterweight champion, “I don’t need the British Medical Association to tell me getting hit on the head can’t do me any good.” Muhammad Ali would surely concur.
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