Perhaps you remember the scene from the 2013 thriller “Escape Plan,” when an inmate played by Arnold Schwarzenegger slugs a fellow prisoner played by Sylvester Stallone, knocking him flat on his back. Stallone gets up, dusts himself off, and delivers one of his famous haymakers to Schwarzenegger’s jaw. Yet the behemoth is unfazed, even laughing.

“You hit like a vegetarian,” he says, in his trademark Austrian-accented English. And while the line may lack the gravitas of “I’ll be back” or even “Hasta la vista, baby,” it resonates enough to get Stallone to try to hit him harder. Because no real man wants to be accused of being an herbivore, right?

This old-fashioned notion that tough guys — and tough women — must eat meat was challenged on Tuesday night at Harvard Law School (HLS), during a screening of the popular documentary “The Game Changers,” which includes the aforementioned clip as a call to vegetarian arms.

Hosted by the Animal Law & Policy Program and the Office for Sustainability, the screening was followed by a panel conversation including some of the athletes profiled in the film, as well as doctors and scientists, all advocating a plant-based diet. The main message? Those who eat a vegetarian, vegan, or plant-based diet pop a wallop, too.

“The Game Changers” trots out a convincing lineup of athletes who swear by plant-based diets, while supporting their anecdotal evidence with serious science from leading researchers and doctors in their fields. World-record-holding strongman Patrik Baboumian; Olympic track-cycling medalist Dotsie Bausch; Australian 400m dash champion Morgan Mitchell; former Tennessee Titans linebacker Derrick Morgan; Scott Jurek, the world’s most accomplished ultramarathoner; professional bodybuilder Nimai Delgado; and Ultimate Fighting Championship winner James Wilks all tout the benefits of eating plant-based, and they each say that making that commitment has played a significant role in their success. Jurek, Delgado, and Wilks (who narrates the film as his own journey to uncover the optimal diet for human performance) were the panelists at the HLS event.

“It’s hard to argue when you win, over and over and over again,” says Jurek, a vegan for the past 20 years who recently set the Appalachian Trail hike speed record, covering its entire 2,189 miles in 46-plus days. Jurek also took the Western States 100 Mile Endurance Run title seven years in a row from 1999-2005.

Delgado, for his part, won the first bodybuilding competition he ever competed in, prompting all kinds of questions as to what he was eating to get “so shredded.” People couldn’t believe that he consumed a vegan diet, including a lot of carbohydrates. Delgado says his competitors were struggling with low energy caused by low-carb diets. “The irony is, you see these guys onstage and their abs and six packs, and they look healthy,” he told the Harvard audience, “but inside they’re rotting.”