- The famously fit actor Dwayne Johnson gained more muscle for "Black Adam," his strength coach said.
- Techniques like pause reps, negatives, and static holds were part of his muscle-building workouts.
Dwayne "The Rock" Johnson took his physique "to a whole other level" for his starring role in DC's "Black Adam" with intense workouts designed to pack on muscle, according to Dave Rienzi, his strength-and-conditioning coach.
To get the already-fit Johnson in even better shape, Rienzi told Insider he used specific techniques to increase muscle tension during each exercise for optimal gains.
Strategies like slowing down each movement, holding a muscle contraction, and lengthening the muscle can help build muscle while avoiding injury, said Rienzi, who is also the cofounder of Johnson's energy-drink brand ZOA. Rienzi's video series, "Building Black Adam," shares more details about the specific workouts in Johnson's training.
"The philosophy I have now isn't about lifting maximal weight, it's about how can I maximally fatigue the muscle with a certain weight, trying to limit the load on the joints. That's where all the time-under-tension techniques come in," he said.
Pause reps create more muscle tension for better gains
To make The Rock even more massive, Rienzi had him focus on pausing at the top of each lift, squeezing the muscles to create tension and prompt more growth.
"Contracting as hard as you can at each peak helps take it to the next level," Rienzi said.
Building muscle with strength training is about continually challenging the muscles, a principle known as progressive overload.
You can increase the difficulty of an exercise by adding more weight or reps to keep making progress — but that's not the only way to get results, according to Rienzi. Slowing down an exercise can make your muscles work harder, which prompts them to grow, he said. To keep good form, you may need to lift slightly less weight, but the exercise should feel just as intense, if not more.
"Lifting a little bit lighter weight with slower, more controlled movements can really make the muscles do more work and have less strain on the joints," he said.
'Negative' reps emphasize the lengthening or lowering portion of exercises
Rienzi said a key part of The Rock's "Black Adam" training was an underrated workout technique known as negatives.
Negatives involve the portion of the exercise where the muscle lengthens, called an eccentric contraction, which research suggests is ideal for building muscle.
Examples include the descent portion of a pull-up or push-up, or extending your arm by your side as you lower the weight in a bicep curl.
"I love negatives. The mental thing with negatives is you're thinking about controlling the weight, or fighting the weight on the way down. You're exerting more effort," Rienzi said. "It's one of the most effective techniques in my opinion."
Static holds help safely make a movement more challenging
Rienzi also put The Rock to work by having him perform static holds under tension, keeping a weight in a fixed position while fighting gravity for a type of muscle contraction known as isometric exercise.
For example, a set of bicep curls might involve alternating sides with one arm curling, and the other holding a dumbbell at a 90 degree angle.
A major benefit of isometric or static exercise is that it can be lower impact on the joints since you're not changing the angle of the joint through the movement. However, you'll still want to incorporate full range of motion exercises for other benefits, including mobility, according to Rienzi.
Using a variety of options in your workouts can help you get the best results for your body and your goals, as long a you focus on the right intensity, he said.
"Trying to push yourself as hard as you can within whatever rep range you're working is how you get results," Rienzi said.