How Fast Should You Lift? What Science Says About Tempo and Muscle Growth
Have you ever slowed down your reps because someone at the gym told you “time under tension” was the key to bigger muscles? Or maybe you’ve been told to move the weight fast to generate more force?
Tempo, the speed at which you perform your reps, is one of the most debated variables in training. But what does the science really say?
A team of researchers led by Dr. Brad Schoenfeld decided to answer this question with a systematic review and meta-analysis, pulling together data from multiple studies to see how rep speed affects muscle growth.
Why Tempo Matters (And Why It Might Not Matter That Much)
Let’s meet two lifters.
James lifts explosively. His bench press reps are quick—he focuses on intent and pushing fast, even under heavy load.
Dan lifts slowly and methodically. He takes 3 seconds up, pauses, and lowers for 4 seconds. He’s aiming for “time under tension” and control.
Who builds more muscle?
According to Schoenfeld’s research, both might get similar results—as long as they train to failure.
The review looked at eight studies comparing different rep durations. They analyzed tempos ranging from very fast (under 1 second per rep) to very slow (over 10 seconds per rep). The key takeaway?
Rep durations between 0.5 to 8 seconds led to similar hypertrophy. Training very slowly—more than 10 seconds per rep—seemed to be less effective.
What About Super-Slow Training?
Some fitness circles promote extremely slow training (e.g., 10-second lifts) as a safer or more intense way to train. But the research suggests it may not provide enough stimulus for maximal muscle growth.
In one study, people who trained with super-slow reps had less type II muscle fiber growth (the fibers most associated with strength and size) than those who used traditional, faster tempos.
Why? Super-slow reps often require you to use lighter loads, which may not recruit high-threshold motor units—the ones you need to target for muscle growth.
So… Does Tempo Matter at All?
Yes and no.
- If you’re lifting in a controlled, consistent way—between 0.5 to 8 seconds per rep—you’re likely fine.
- Training to failure is far more important than the exact rep speed.
- Going super slow (10+ seconds) may compromise gains unless there’s a therapeutic or safety reason to do it.
In other words: tempo matters less than effort and intensity.
Practical Takeaways for Your Training
Let’s say you’re training to build muscle. Here’s what you can apply today:
1. Use a Controlled but Natural Tempo
Most of your reps can follow a rough 2–3 second eccentric (lowering) and 1–2 second concentric (lifting) rhythm. No need to count precisely—just avoid bouncing or rushing.
2. Train to or Near Failure
Whatever your tempo, bring your sets close to muscular failure. That’s where motor unit recruitment and muscle fiber activation peaks.
3. Avoid Super-Slow Unless There’s a Specific Reason
If you’re rehabbing, learning technique, or training under load limitations, slower reps may be helpful. But don’t expect them to build more muscle.
4. Match Tempo to Intent
If you’re lifting heavy, your reps will slow down naturally. If you’re doing higher reps, you might have more freedom to experiment with tempo—just don’t let it compromise effort.
5. Consistency Beats Obsession
Focus more on showing up, training hard, and recovering well than obsessing over seconds per rep.
Final Thoughts
Tempo isn’t magic. It’s a tool.
Schoenfeld’s research makes one thing clear: you don’t need a stopwatch to grow muscle—you need effort, consistency, and progressive overload.
So next time someone debates whether 4–0–2 or 2–1–2 is the superior tempo, just remember: as long as you train with intent and push yourself, your muscles won’t be counting seconds—they’ll be growing.
References
- Schoenfeld, B. J., Ogborn, D. I., & Krieger, J. W. (2015). Effect of Repetition Duration During Resistance Training on Muscle Hypertrophy: A Systematic Review and Meta-Analysis. Sports Medicine, 45(4), 577–585. https://doi.org/10.1007/s40279-015-0304-0
- Schuenke, M. D., Herman, J. R., et al. (2012). Early-phase muscular adaptations in response to slow-speed versus traditional resistance-training regimens. European Journal of Applied Physiology, 112(10), 3585–3595.
