Dwayne Johnson has undergone one of the most extreme physical transformations of his career — and even his trainer says it pushed new limits.
Preparing to play real-life MMA fighter Mark Kerr in The Smashing Machine, Johnson was given an unusual request from director Benny Safdie: get even bigger.
For a man already known as one of Hollywood’s most muscular stars, that meant taking things to another level entirely.
Working alongside long-time trainer Dave Rienzi, Johnson had around six months to completely reshape his body — not just to look like Kerr, but to move and perform like him too.
The training programme was intense. It included high-volume workouts, extra shoulder-focused sessions, and heavy trap-building exercises multiple times a week to replicate Kerr’s iconic physique. The goal wasn’t just size — it was accuracy.
Rienzi revealed that they studied footage of Kerr closely, focusing on key features like his massive shoulders and explosive power inside the ring.
But building muscle was only part of the challenge.
Johnson also had to maintain speed, endurance, and mobility while filming demanding fight scenes and preparing for wrestling appearances. That meant combining strength training with explosive movements, MMA-style drills, and regular cardio sessions.
His diet was just as extreme.
To fuel the transformation, Johnson consumed six to seven whole-food meals a day, plus additional shakes — all carefully balanced to build muscle without unnecessary fat gain. According to Rienzi, it was the most food Johnson has ever eaten for a role.
Filming itself added another layer of difficulty, with weeks of fight scenes taking a toll on his body. Despite the physical strain, Johnson remained committed — even going as far as taking real hits during filming to make scenes look authentic.
The result is what many are calling one of the most impressive transformations of his career, with critics praising both his physical resemblance to Kerr and his performance in the role.
Behind it all, Rienzi says one trait stands out above everything else: consistency.
No matter how busy his schedule gets, Johnson never skips training — a level of discipline that continues to set him apart in Hollywood.
