Arnold Schwarzenegger still aims to build muscle at 78 in retirement. In Arnold’s Pump Club newsletter from May 28, 2026, he broke down why some people build muscle faster than others.
“You know someone like this: they seemingly follow the same program as you, eat their protein, show up consistently, and still build twice the muscle in half the time.”
As a former seven-time Mr. Olympia, Schwarzenegger conquered the sport during the Golden Era, proving himself against legends like Frank Zane and Sergio Oliva. It’s been decades since he competed, but Schwarzenegger still pays close attention to his health and longevity inside and outside the gym.
Arnold Schwarzenegger Breaks Down Why Some People Respond Better to Weight Training
In the newsletter, he explained why testosterone, sex, and genetics aren’t the biggest predictors of muscle building.
“The biggest predictor of who builds muscle is not testosterone, sex, or genetics. It appears to be what happens inside individual muscle cells in the earliest stages of training, and you have much more control over your muscle-building potential than you might believe.”
Researchers believe some people build more muscle than others because of how the body uses ribosomes, or tiny structures within cells.
“Researchers from over a dozen independent labs synthesized more than two decades of evidence on why people following identical resistance training programs see such different results. Their most consistent finding across multiple independent groups is that higher responders appear to build more ribosomes from the very first workout. Ribosomes are the cellular machinery that manufactures proteins, the construction crew inside your muscle.”
“Lower responders show compromised ribosome accumulation early on. One analysis found that high responders were the only group to register measurable ribosome-related content after just a single exercise session.”
Surprisingly, researchers found that testosterone levels and diet in younger adults had no significant impact on who responded better to training.
“What researchers didn’t find is equally important: testosterone levels in younger adults showed no meaningful association with who responds better to training. Neither did habitual diet.
“Researchers don’t yet have a specific protocol for accelerating that process. What they do know is that the same levers driving muscle growth generally — volume, proximity to failure, consistency — also appear to reduce the prevalence of low responsiveness. The signal may simply need to be stronger and more sustained before it registers.”
If you’re a slow gainer, Schwarzenegger said you can break through the plateau with a more persistent training plan.
“Here’s the good news: The cells aren’t broken if you’re not a hyper-responder. They just need more. Specifically, you may need a larger, more persistent training stimulus before they get to work. That’s a very different problem from assuming you’ve hit some kind of ceiling. It means some people respond faster, not that others can’t respond meaningfully.”
“What researchers didn’t find is equally important: testosterone levels in younger adults showed no meaningful association with who responds better. Neither did habitual diet. And while aging does create real biological changes that can affect responsiveness, chronological age alone doesn’t determine your outcome.”
Even for older adults, he noted that a higher-volume training routine helped those who struggle to build muscle:
“Older adults are not condemned to low responsiveness. And many people labeled “non-responders” in shorter studies were likely misclassified. When measurement error is accounted for and training volume is increased, the category of true non-responder shrinks considerably.”
Schwarzenegger emphasized that mechanical tension drives muscle growth, along with taking your sets to near-failure.
“The primary driver of muscle growth is mechanical tension: the force your muscle generates working against a load, especially in a lengthened position. That tension is what signals ribosomes to get to work.”
But tension alone doesn’t do much if you stop three or four reps short every set, which is where the real stimulus lives. Research consistently shows that training within about 1-2 reps of your actual limit maximizes hypertrophy. Going all the way to failure on every set provides no measurable benefit and costs you recovery time.”
Schwarzenegger has also sought out strategies for burning fat and building muscle simultaneously. He examined a study involving three groups and found that those who ate the most protein managed to burn fat and build the most muscle.
Muscle building can vary in time, depending on a variety of factors like sex, genetics, and hormone fluctuations. Schwarzenegger believes that mechanical tension, consistency, and effort are the most important cornerstones of progress.
RELATED: Arnold Schwarzenegger Shares If Soy Protein is Inferior for Muscle Gains vs Dairy
