Slow vs Fast Reps: Which Builds More Muscle?
4 min read
What’s the better approach for muscle growth—slow and steady, or fast and explosive? This question has sparked debate in gyms and strength circles for years. And recently, fitness educator Jeff Cavaliere (Athlean-X) tackled the topic in a new video that breaks down both styles of lifting and their role in hypertrophy (aka, muscle growth).
Here’s what you need to know:
The Case for Slow Reps
Slowing down your reps increases time under tension—a key factor in stimulating hypertrophy. Cavaliere outlines a method that gradually increases tempo:
Start with a 1-second concentric (lifting phase) and 1-second eccentric (lowering phase)
By the fifth rep, you're at a 5-second up / 5-second down tempo
Then, reverse the tempo back down until you’ve completed 10 reps total
That structure creates about 60 seconds of muscle tension per set, which is an excellent benchmark for triggering growth.
Slower reps don’t just burn more—they also help you develop control, improve form, and build a strong mind-muscle connection, all of which support long-term gains.
The Case for Fast Reps
Fast-paced reps can allow you to lift heavier loads—especially during the concentric phase—by using speed and momentum. This approach targets the fast-twitch muscle fibers, which are responsible for power and size.
But there’s a caveat: control matters. Even if you move quickly on the way up, it’s essential to slow things down on the way down (the eccentric phase). That’s where the real muscle damage—and growth—happens.
Common Mistakes to Avoid
Cavaliere also points out a common pitfall: partial reps done at lightning speed with little attention to form or control. While this might feel effective, it only works if you’re truly pushing to muscular failure—and even then, it’s not a strategy you want to rely on all the time.
So… Which Is Better?
Here’s the good news: both slow and fast reps have their place. The key is to understand what your goal is and how to execute each method properly. If you want more muscle, combining both approaches can give you the best of both worlds—slow reps for control and endurance, fast reps for power and strength.
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