Bodybuilding legend Arnold Schwarzenegger is uncovering the truth behind slower reps, revealing if they lead to better gains. On February 19, 2025, he shared that slowing down repetitions won’t lead to more muscle growth. Instead, he said hypertrophy is maximized by mechanical tension.
“If you’re slowing reps down on purpose, you might just be making your workout feel harder without making it more effective.”
Arnold Schwarzenegger won the prestigious Mr. Olympia contest seven times throughout his career. He is considered the most famous and successful athlete to emerge from the IFBB Pro League.
In retirement, he remains dedicated to growing the sport of bodybuilding, especially with his Arnold’s Pump Club Newsletter, which offers fans curated fitness advice backed up by scientific research.
Arnold Schwarzenegger Says Slower Reps Don’t Mean More Muscle Growth: “That’s Not How It Works”
View this post on InstagramGet Fitter, FasterLevel Up Your Fitness: Join our 💪 strong community in Fitness Volt Newsletter. Get daily inspiration, expert-backed workouts, nutrition tips, the latest in strength sports, and the support you need to reach your goals. Subscribe for free!
In his latest Arnold’s Pump Club Newsletter, Schwarzenegger revealed why slower reps don’t equal more muscle growth. He emphasized that mechanical tension is key to maximizing hypertrophy.
“The Truth About Slow Reps and Muscle Growth
Some people believe that slowing down their reps will help build more muscle. The idea makes sense on the surface—more time under tension should mean more growth. But that’s not how it works.Research suggests that intentionally slow, controlled reps don’t lead to more muscle growth because they don’t create the mechanical tension needed to maximize hypertrophy.”
He posits that unintentionally slow reps are what matter most when it comes to building muscle.
“Instead, the unintentionally slow reps—when your muscles struggle to move the weight—are the ones that matter most.
If you use a lighter weight and move that weight slowly on purpose — to increase time under tension — you are applying less force than you could. That means the stimulus your muscles need to grow is less than ideal.”
He revealed that mechanical tension and pushing the body to experience more strain are the stimuli needed to grow.
“Researchers have found that mechanical tension is the primary driver of muscle growth. When you lift heavier weights or push lighter weights to failure, your muscles experience higher levels of mechanical strain. This forces your body to recruit more motor units, especially the high-threshold ones responsible for muscle growth.”
“So, you can grow with high reps and lower weight or with lower reps and higher weight. But this is where people get confused and think they should just slow down the pace of their reps.”
Although the concept of time under tension has been popularized in the fitness sector, he shared that with lighter weights and slower reps, lifters aren’t applying the necessary force to grow their muscles.
“It’s good to think about muscle growth as a game where you win by applying more force. If you use a lighter weight and move that weight slowly on purpose — to increase time under tension — you are applying less force than you could. That means the stimulus your muscles need to grow is less than ideal.
“The problem is that those slow reps are making your muscles burn. So it feels like it’s working, but it’s deceiving.”
Another study illustrated that intentionally slowing down reps only increased the perception of fatigue, not mechanical tension.
“A different study found that intentionally slowing down reps increases the perception of fatigue but doesn’t necessarily increase mechanical tension or motor unit recruitment. In other words, it makes the set feel harder, but that doesn’t mean it’s more effective.”
He says slow reps are effective for muscle growth when lifters reach fatigue and can no longer move the weight quickly.
“When your muscles are working so hard and have achieved enough fatigue that they cannot move the weight quickly, that’s the type of “slow reps” that are effective.
These “hard reps” are where mechanical tension peaks, rep speed unintentionally slows down, and you’re maximizing muscle growth.”
He believes finding the right balance of intensity and fatigue is key to making gains.
“As a rule of thumb, you want the last 1 to 3 reps of any set to be the “hard reps,” where you still can control the weight, but you’ve found the right balance between intensity and fatigue to maximize force and tension.
It’s why the most popular article in The Pump app is “first set mindset.” It’s the idea that you approach each and every set like it’s your first and only set, so you can learn how to push yourself as needed.”
As general guidance, he recommends not forcing slow reps, but instead focusing on controlled explosive movements throughout the concentric phase of an exercise.
“To make the most of every session, remember:
Don’t force slow reps—focus on controlled but explosive movements during the concentric phase (lifting the weight).”
He urges those aiming for muscle growth to push to failure so that their reps slow down naturally.
“Push sets close to failure to ensure you reach those reps where your movement slows down naturally.
Use loads heavy enough (65-85% of your 1-rep max) to challenge your muscles and force high-threshold motor unit recruitment. There are exceptions to the rules and times when you might need to use lighter weights (such as with injury). And remember, strength is relative to your ability. What is light for one person can be heavy for another, and as long as it’s challenging to you, that’s all that matters.”
Schwarzenegger continues to offer his fanbase useful advice for bettering their health and physiques. Instead of executing intentionally slower repetitions, he stands by pursuing failure until your reps slow down for optimal muscle growth results.
You can also follow us on Twitter, Facebook, Instagram, and
YouTube for even more content.
