The Study
Effect of different eccentric tempos on hypertrophy and strength of the lower limbs
This study found that if you lift weights slowly for 4 seconds vs 2 seconds on one leg, your thigh muscle in one spot (vastus medialis) might grow a tiny bit more — but the rest of your leg muscles and your strength didn’t change much. It doesn’t prove one way is better overall — just that this one small difference happened in this one group.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
People did leg extensions with either a slow (4-second) or fast (2-second) downward motion for 8 weeks to see if one made their thigh muscles grow more.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 554 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1The difference in muscle growth was small and only in one part of the thigh — not enough to matter for most people trying to build overall leg size or strength.
- 2The inner thigh muscle (vastus medialis) grew a little more with the slow motion (4s), but the outer and front thigh muscles grew the same.
- 3Strength didn't change between slow and fast.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Biology of Sport
Year
2021
Authors
P. Azevedo, M. G. D. Oliveira, B. Schoenfeld
Related Content
Claims (6)
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.
If you're a young adult who doesn't lift regularly and you do leg extensions slowly (4 seconds down), your inner thigh muscle gets a little thicker than if you do it faster (2 seconds down)—but the outer and front thigh muscles don't change much.
If you're a young adult who hasn't trained before and you do leg extensions slowly—either taking 2 seconds or 4 seconds to lower the weight—your thigh muscles will grow about the same amount, and you'll get just as strong either way.
If you're a young adult who hasn't trained much before, slowing down the lowering part of a leg extension from 2 seconds to 4 seconds won't make you significantly stronger, even though your muscle is under tension longer.
When you lower a weight slowly (like 4 seconds), your inner thigh muscle (vastus medialis) grows more than the other thigh muscles — the others don’t seem to care as much about the slow lowering.
If you take four seconds to lower the weight during leg extensions instead of two seconds, your muscles are under strain for about 95% longer—without doing more reps—over eight weeks of training.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.