The Claim
Concentric-only resistance training at moderate volume results in significantly smaller increases in muscle thickness (2.5%) compared to eccentric-only or concentric-eccentric training (9–11%) in untrained young adults after five weeks, indicating that concentric contractions alone are insufficient to drive substantial hypertrophy under these conditions.
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.
After five weeks of moderate-volume resistance training, untrained young adults who performed only concentric movements gained 2.5% less muscle thickness than those who performed eccentric-only or combined concentric-eccentric movements.
See the scientific wording
Concentric-only resistance training at moderate volume produces significantly smaller increases in muscle thickness (2.5%) compared to eccentric-only or concentric-eccentric training (9–11%) in untrained young adults after five weeks, indicating that concentric contractions alone are insufficient to drive substantial hypertrophy under these conditions.
When muscles lengthen under load, they experience high tension that activates signals inside muscle cells, turning on a system that builds more contractile proteins. This increases the size of muscle fibers. Concentric contractions do not create enough tension to trigger this system strongly, so they cause little growth.
What the research says
1 studyLifting a weight up without lowering it slowly only makes muscles grow a tiny bit — just 2.5% — but lowering it slowly (even without lifting) makes them grow almost 10%, just like doing both. So, lowering weights is way more important for building muscle than just lifting them.
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.