The Claim
In untrained young adults, performing barbell squats with a 4-second eccentric phase for 7 weeks results in a significantly greater increase in vastus lateralis muscle cross-sectional area compared to performing the same exercise with a 1-second eccentric phase, with effect sizes of 1.74 and 1.37, respectively.
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 untrained young adults, doing barbell squats with a 4-second lowering phase for 7 weeks causes a larger increase in the size of the vastus lateralis muscle than doing the same squats with a 1-second lowering phase.
See the scientific wording
In untrained young adults, performing barbell squats with a 4-second eccentric phase for 7 weeks leads to a significantly greater increase in vastus lateralis muscle cross-sectional area (effect size = 1.74) compared to a 1-second eccentric phase (effect size = 1.37), suggesting that prolonged eccentric tension may preferentially stimulate hypertrophy in this specific quadriceps muscle.
When the muscle is stretched slowly under load, the fibers experience longer tension, which activates the slow-twitch fibers more than the fast-twitch ones. These slow fibers grow larger because the sustained stress triggers signals that build more muscle protein, leading to thicker muscle fibers and increased muscle size.
What the research says
1 studyIn a study where people did squats with a slow vs. fast lowering phase, those who lowered the bar slowly for 4 seconds ended up with bigger thigh muscles than those who lowered it quickly for 1 second.
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.