House of Hypertrophy
Rep speed doesn't significantly affect muscle growth when training close to failure, but super-slow protocols may reduce gains.
Muscle growth is similar across a wide range of rep speeds when training to failure, but extremely slow tempos with light weights appear less effective.
We checked the science
our breakdown of the video
10 claims, each mapped to its moment in the video
To figure out whether speeding up or slowing down the lifting vs. lowering part of a weight workout makes your muscles grow more, scientists need to test each part separately—not at the same time.
Multiple causal studies (randomized trials and reviews) support this claim.
Lifting weights fast or slow doesn’t make much difference in how much your muscles grow — the extra gain from going slow is practically nothing.
Multiple causal studies (randomized trials and reviews) support this claim.
When people lift weights without going all the way to exhaustion, using machines that force a set speed might make fast lifting look better—but that’s because those machines don’t act like real free weights or gym machines we usually use.
Not enough evidence yet — take this with caution.
When you first start lifting weights, you get stronger not because your muscles grow bigger right away, but because your brain gets better at telling your muscles when and how to contract.
Evidence contradicts this claim.
When people lift weights regularly, their muscles usually get about 5% bigger on average, no matter what kind of weight routine they follow.
Evidence points in both directions — no clear conclusion yet.
How fast or slow you lift and lower weights doesn’t matter as much for building muscle as how much weight you lift, how many reps you do, or how close you push yourself to failure.
Evidence contradicts this claim.
If you lift and lower weights quickly or slowly, as long as you do both phases the same way, your muscles grow about the same amount—speed doesn’t make a big difference.
Multiple causal studies (randomized trials and reviews) support this claim.
If you lift weights until you're really tired, it doesn't matter if you lift slowly or quickly—you'll still build about the same amount of muscle.
Good evidence supports this claim, with little to contradict it.
Lifting weights really slowly with lighter weights doesn’t build as much muscle as lifting heavier weights at a normal speed—even if you push yourself to the limit in both cases.
Not enough evidence yet — take this with caution.
You can build muscle just as well lifting light weights as heavy ones — as long as you push yourself until you can’t do another rep.
Multiple causal studies (randomized trials and reviews) support this claim.
Key Takeaways
Summary
Based on the video transcript only.
- 1Problem: People think slowing down reps makes muscles grow bigger, but it’s unclear if speed actually matters.
- 2Core methods: Faster eccentric tempo, slower eccentric tempo, faster concentric tempo, slower concentric tempo, super-slow training (10s concentric, 4s eccentric), training to failure.
- 3How methods work: Faster tempos reduce time under tension per rep; slower tempos increase it; super-slow uses very long durations with lighter weights; training to failure means pushing until you can’t do another rep, which stresses muscles enough to grow regardless of speed.
- 4Expected outcomes: Muscle growth is about 5% on average, whether using fast or slow tempos; super-slow training led to less muscle fiber growth in one study.
- 5Implementation timeframe: Muscle growth occurs over weeks to months; no specific timeframe is given, but results are similar regardless of tempo as long as training is intense enough.
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