10 On-Set Injuries You Won’t Believe Actors Worked Through

9. Sylvester Stallone - Swollen Heart - Rocky IV

When you're got Sylvester Stallone and Dolph Lundgren in a movie, you have to expect a certain amount of tough guy shenanigans. But what happened in Rocky IV defied expectations. While they were preparing to film the climactic fight scene, they decided together that they wanted a certain degree of authenticity to their action sequences. But how to achieve it? Although it may not have been the wisest plan looking back, they elected to have Dolph throw one real punch during the fight. Which seemed cool, until the impact of the blow on Sylvester Stallone's chest made his heart swell and caused a trip to the emergency room. Well, hindsight is 20/20, right? To this day, Stallone cites this injury as his worst, which for a guy who has also broken his neck and torn his chest muscles, that's saying something. His rendezvous with Dolph Lundgren's fist ended with the Italian Stallion spending eight days in intensive care, and likely would have killed him had he not sought medical treatment fairly soon after the injury occurred.