The Claim
In untrained adults, resistance training with a 1-second eccentric phase produces the same increase in biceps brachii muscle thickness as resistance training with a 4-second eccentric phase, with both conditions resulting in approximately 15–18% hypertrophy, indicating no difference in muscle hypertrophy due to eccentric phase duration.
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.
In people who have not trained before, lifting weights with a 1-second or 4-second lowering phase results in the same amount of biceps muscle growth, around 15–18%.
See the scientific wording
In untrained adults, resistance training with either a 1-second or 4-second eccentric phase produces equivalent increases in biceps brachii muscle thickness (approximately 15–18%), indicating that eccentric phase duration does not influence muscle hypertrophy in novice lifters.
When someone lifts weights, the stretching and pulling of muscle fibers during exercise triggers signals inside the muscle cells that tell them to build more protein, making the fibers thicker. This happens whether the weight is lowered slowly or quickly, because the total force and stretch on the muscle are enough to start the growth process either way.
What the research says
1 studyIn people new to weightlifting, whether you lower the weight slowly or quickly during bicep curls, your biceps grow about the same amount—speed doesn’t matter for muscle size.
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.