The Claim
In untrained young adults performing unilateral knee extensions, a 4-second eccentric tempo results in a small but statistically significant increase in vastus medialis muscle thickness compared to a 2-second eccentric tempo (Hedges’ g = 0.47), with no meaningful difference observed in vastus lateralis or rectus femoris muscle thickness.
What the research says
Supports is higher
Support is ahead, but a single strong opposing study can change this.
These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.
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.
See the scientific wording
In untrained young adults performing unilateral knee extensions, a 4-second eccentric tempo produces a small but statistically significant increase in vastus medialis muscle thickness compared to a 2-second eccentric tempo (Hedges’ g = 0.47), while no meaningful difference is observed in the vastus lateralis or rectus femoris.
What the research says
1 studyStudy: Effect of different eccentric tempos on hypertrophy and strength of the lower limbs
This study found that slowing down the lowering part of knee extensions made one specific knee muscle (vastus medialis) grow a little more than usual, but didn’t help the other thigh muscles — just like the claim said.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.