1 of 4 | Dwayne Johnson attends the premiere of “The Smashing Machine” at the 82nd Venice Film Festival in Italy on Sept. 1. Photo by Rune Hellestad/UPI | License Photo
As a former wrestler, Dwayne Johnson has made an acting career for himself by playing strong and physically imposing characters on screen.
But transforming into former MMA and UFC fighter Mark Kerr for the new film The Smashing Machine required Johnson to put on an additional 30 pounds of muscle. After a wig and 22 prosthetics, Johnson is nearly unrecognizable in the role as Kerr, a two-time UFC Heavyweight Tournament Champion.
The Smashing Machine, which follows Kerr’s career as well as his personal struggles with addiction, comes to theaters Friday. The film also stars Emily Blunt as Kerr’s wife, Dawn Staples, and is directed by Benny Safdie.
Johnson’s not the only actor to take on the physical transformation required to portray some of history’s most iconic fighters.
Here’s a look at seven other actors who got in shape to play legendary MMA fighters and boxers:
Christy (2025)
Like most actors who take on physical roles, Sydney Sweeney said she trained two or three times each day to play boxer Christy Martin. She also worked with a nutritionist, though her diet was a little unusual for the typical actor.
“There was a lot of Chick-fil-A,” director David Michôd told attendees at the Toronto Film Festival, where Christy premiered in September.
“A lot of Smuckers, a lot of milkshakes, a lot of protein shakes,” Sweeney added. “But it was incredible being able to completely embody such a powerful woman.”
Also starring Ben Foster as Martin’s abusive husband, the film hits theaters Nov. 7.
Sydney Sweeney (L) and Christy Salters Martin attend the premiere of “Christy” during the Toronto International Film Festival at the Princess of Wales Theatre in Canada on September 5. Photo by Chris Chew/UPI
Fire Inside (2024)
Actor Ryan Destiny said she went from barely being able to do one push-up to lighting up the screen as boxer-turned-MMA fighter Claressa Shields in The Fire Inside.
Shields told UPI that a training montage showing Destiny in the ring, running, doing push-ups, crunches and more was all authentically her. She said Destiny sought advice from her on how to cope with soreness after filming the scenes.
“Go and get a massage, ice bath, hot bath, rest, drink some water,” Shields said. “It’s OK to recover. I think a lot of athletes should do more recovery.”
Boxer Claressa Shields (L) and actor Ryan Destiny attend the premiere of “The Fire Inside” at the Directors Guild Theater in Los Angeles on December 4. File Photo by Jim Ruymen/UPI
Bleed for This (2016)
Miles Teller underwent intense dieting and training to drop from 188 pounds and 20% body fat to a leaner 168 pounds and 6% body fat for his performance as boxer Vinny Pazienza in Bleed for This.
He told Men’s Journal he worked with a nutritionist and trainer to lose weight, get a boxer’s build and even learn to take a punch. He said he was surprised how difficult it was to train himself not to flinch when he sees a punch coming.
Bleed for This tells the story of Pazienza, “The Pazmanian Devil,” a successful boxer sidelined by a devastating neck injury in a car crash. He ignores doctors’ advice not to return to the ring.
The Fighter (2010)
Christian Bale has become well known for his extreme body transformations for his on-screen roles. He dropped 60 pounds to play an emaciated insomniac in The Machinist in 2004, bulked back up for his first turn as Batman in 2005, and dropped back down again to portray the former addict and convict Dicky Eklund in The Fighter.
Eklund’s troubles with drugs and the laws cost him his boxing career, but The Fighter tells the story of how he turned his efforts toward training his brother, Micky Ward (Mark Wahlberg).
Bale’s turn as the beleaguered boxer earned him an Academy Award and a Golden Globe for Best Actor.
Dicky Eklund (L) and Christian Bale (R) attend the premiere of “The Fighter” at the Grauman’s Chinese Theatre in the Hollywood section of Los Angeles on December 6, 2010. File Photo by Phil McCarten/UPI
Cinderella Man (2005)
Actor Russell Crowe went so far in his training to play heavyweight boxing champion James J. Braddock that he injured himself ahead of filming.
While training in Sydney, Crowe dislocated his shoulder, which required him to undergo surgery. The incident held up filming of Ron Howard’s Cinderella Man for weeks.
A year after the injury, Crowe — who had a reputation for aggressive behavior and bar brawls at the time — said he never wanted to fight again.
“What I took away from filming Cinderella Man is realizing that getting punched in the head is stupid,” he said. “It’s not something I ever want to do again.”
While the film didn’t do as well as expected at the box office, it received a slew of nominations during the 2005 awards season. Paul Giamatti took home Best Supporting Actor awards at the Critics’ Choice Awards and Screen Actors Guild Awards.
Russell Crowe and Renee Zellweger arrive for the June 1, 2005, New York premiere of their film “Cinderella Man” File Photo by Ezio Petersen/UPI
Ali (2001)
Will Smith’s transformation into boxing legend Muhammad Ali was so authentic, even Ali’s own daughter was fooled.
“She said it took her 20 minutes after the movie to realize she actually wasn’t watching Daddy,” Smith told UPI in 2002. “She said 20 minutes after the film, it dawned on her that, ‘Wait a minute. That was Will. That wasn’t Daddy.’ And that was the ultimate compliment.”
Smith said he not only underwent physical training to play the iconic role, he also had to train mentally and emotionally. Ultimately, he spent a year training, gained 35 pounds and did all his own stunts for the role.
And it all paid off. Smith earned his first Academy Award nomination for his performance.
Will Smith is named actor of the year at ShoWest 2002 at Paris in Las Vegas on March 7, 2002, for his role in “Ali.” File Photo by Roger Williams/UPI
Raging Bull (1980)
Perhaps the most iconic boxing movie of all time, Raging Bull stars Robert De Niro as legendary middleweight boxer Jake LaMotta. Speaking on the Off Menu Podcast in May, De Niro said he packed on a whopping 60 pounds for the part.
“When I was getting the weight, I had to eat in the morning three full meals, which was hard to do, and then digest the food, to eat lunch and then dinner,” De Niro said. “It’s kind of fun for the first 10, 12, 15 pounds, and [then] it’s drudgery.”
The commitment was worth it, though. De Niro’s turn as LaMotta earned him his only Best Actor award at the Academy Awards.
Robert Deniro (L), Cathy Moriarty (2nd-L), Jake Lamotta (2nd-R) and Martin Scorsese reunite for a 25th anniversary screening of their film “Raging Bull” at the Ziegfeld Theater in New York on January 27, 2005. File Photo by Laura Cavanaugh/UPI
