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.
Evidence from Studies
Supporting (2)
Community contributions welcome
Effect of Repetition Duration During Resistance Training on Muscle Hypertrophy: A Systematic Review and Meta-Analysis
This study found that whether you lift weights slowly or quickly (as long as it’s not super slow), your muscles grow about the same amount — so the speed doesn’t really matter for building muscle.
How Slow Should You Go? A Systematic Review With Meta-Analysis of the Effect of Resistance Training Repetition Tempo on Muscle Hypertrophy
This study found that whether you lift weights slowly or quickly, your muscles grow about the same amount — so speeding up or slowing down your reps doesn’t really make a difference in building muscle size.
Contradicting (1)
Community contributions welcome
The study says how fast you lift weights matters for muscle growth, but it doesn’t say whether fast and slow lifting make almost the same amount of muscle gain — so we can’t tell if the claim is right or wrong.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.